Camshaft Discussion part II
09-13-2004, 08:42 PM
#402
I saw this in the Cyl Heads post but was right on point for here. This was posted by Greg Good:
First off, I think we are taught the "cycles" of a four cycle engine in the wrong order. The first cycle discussed is always the intake stroke, and the nice pictures in the books always show the engine starting off with a clean and thoroughly exhausted cylinder. That is the ideal situation, but it is not how it always happens in real life. The "cycles", in reality, should be taught with the exhaust cycle first. Now, the intake valve opens in the latter stage of the exhaust phase, against residual pressure that's left over from the exhaust phase prior to the intake opening point. The amount of this residual pressure is directly determined by how well the combination of exhaust port, header, and camshaft did their jobs. If they did not do their job, and a high residual pressure is present when the intake valve opens, exhaust gases flow into the intake port. This is the worst thing you could ever have happen. The higher the rpm, the worse it gets. Exhaust gases that enter the intake port displace and contaminate fresh air and fuel, and also counter the velocity in the intake port. You will never have a good intake stroke unless the exhaust stroke before it was a good one. Heads with larger intake valves are more sensitive to exhaust reversion because they flow more air "backwards" at low lift. Any good head porter, when R&D'ing for a better valve job, always takes low lift reverse intake flow into consideration because it determines the rate at which exhaust reversion can get into the intake port during the initial phase of overlap.
The most important part of the exhaust stroke is the blowdown period. From the first point of exhaust opening to BDC I want all the valve lift the cam grinder can give me, and all the flow I can get out of the port at the lifts seen during this time. The blowdown period is the best time to get exhaust flow out because it is leaving the cylinder under its own pressure and the piston is not having to push it out. The valve has not reached full lift by BDC so that means that you need really good mid-lift flow to help the blowdown period. I like for my exhaust ports to "come on" at as low a lift as possible. The valve job, venturi size, and chamber shrouding control this. I've changed valve jobs to increase mid-lift flow. I've run intake lobes with their faster ramps on the exhaust to gain more lift at BDC. It works for me.
Beyond blowdown on the rest of the exhaust stroke, where the piston is pushing the exhaust out, high lift exhaust flow determines how easily the remainder of exhaust gets pumped out. So, the better the high lift cfm number, the less work the engine has to do to get the piston to TDC. When everything is working right, and the port flows enough, and the valve opens just soon enough, the less residual pressure the intake valve sees, and the less exhaust gas enters the intake port.
How much exhaust flow does a guy need? Depends on the application. You guys running street engines on pump gas (low compression) need a pretty high percentage in my opinion to get the job done. Low compression engines do not like an early exhaust opening. The exhaust valve opens during the latter stage of the power stroke. An exhaust valve that opens too early shortens the power stroke and hurts power. That's why the cams you see that are running good on low compression street engines typically have exhaust lobes that are close in duration to the intake lobes.
An engine with high compression, such as 15:1 or 16:1, is not very sensitive at all to exhaust opening point, and we can run 25-30 degrees more duration on the exhaust than the intake. In that case we'll set up the heads to favor the intake ports by cutting down the exhaust valve and increasing the intake valve size. When you are able to run 25 degrees more duration on the exhaust you can get by with 65% of the intake port for exhaust flow. The extra cam duration makes up for the weaker exhaust flow.
The most important part of the exhaust stroke is the blowdown period. From the first point of exhaust opening to BDC I want all the valve lift the cam grinder can give me, and all the flow I can get out of the port at the lifts seen during this time. The blowdown period is the best time to get exhaust flow out because it is leaving the cylinder under its own pressure and the piston is not having to push it out. The valve has not reached full lift by BDC so that means that you need really good mid-lift flow to help the blowdown period. I like for my exhaust ports to "come on" at as low a lift as possible. The valve job, venturi size, and chamber shrouding control this. I've changed valve jobs to increase mid-lift flow. I've run intake lobes with their faster ramps on the exhaust to gain more lift at BDC. It works for me.
Beyond blowdown on the rest of the exhaust stroke, where the piston is pushing the exhaust out, high lift exhaust flow determines how easily the remainder of exhaust gets pumped out. So, the better the high lift cfm number, the less work the engine has to do to get the piston to TDC. When everything is working right, and the port flows enough, and the valve opens just soon enough, the less residual pressure the intake valve sees, and the less exhaust gas enters the intake port.
How much exhaust flow does a guy need? Depends on the application. You guys running street engines on pump gas (low compression) need a pretty high percentage in my opinion to get the job done. Low compression engines do not like an early exhaust opening. The exhaust valve opens during the latter stage of the power stroke. An exhaust valve that opens too early shortens the power stroke and hurts power. That's why the cams you see that are running good on low compression street engines typically have exhaust lobes that are close in duration to the intake lobes.
An engine with high compression, such as 15:1 or 16:1, is not very sensitive at all to exhaust opening point, and we can run 25-30 degrees more duration on the exhaust than the intake. In that case we'll set up the heads to favor the intake ports by cutting down the exhaust valve and increasing the intake valve size. When you are able to run 25 degrees more duration on the exhaust you can get by with 65% of the intake port for exhaust flow. The extra cam duration makes up for the weaker exhaust flow.
10-08-2004, 09:50 PM
#403
6600 rpm clutch dump of death Administrator
Thread Starter
Found these threads thanks to a link from 383lq4SS (thanks BTW) from this thread on mid lift numbers
https://ls1tech.com/forums/generation-iii-internal-engine/223995-importance-mid-lift-flow-numbers.html
Anyhow, it references another thread.
http://www.eng-tips.com/viewthread.cfm?qid=92513
which has some good info from Larry Meaux of Meaux Racing Heads in Louisiana.
The references a thread which has info from Darin Morgan of Reher Morrison
http://speedtalk.com/forum/viewtopic.php?t=321
Here is some of the more important info...
http://www.eng-tips.com/viewthread.cfm?qid=92513
Rick360 (Electrical) Apr 14, 2004
When porting a set of heads there are ways to enhance high, mid or low lift flow characteristics. I realize the ideal is to gain at all lifts but sometimes there is a tradeoff.
Which one would you trade for what other one? and why?
I profiled a cam which has .800" net lift thru its entire lift curve to see how long the valve was at what point, the piston velocity, and the flow at that lift. I then calculated theoretical flows throughout the intake stroke to see which lift points made the bigger difference. It seems that .700" and up had a bigger effect. Does this hold true on a dyno? Would gaining 10cfm at .7" - .8" be worth giving up 10 cfm at .5"-.6"?
Rick
Start Your Own Eng-Tips Group! Click Here!
SMOKEY44211 (Automotive) Apr 15, 2004
I have found the biggest single factor affecting low, mid and high lift flow is the valve seat angle. Shallow angles (15-30deg)tend to favor low lift flow. In some racing classes where the cam may be lift restricted there is some gain to optimizing low lift flow. Current trend in Pro stock drag class seems to favor steep (55deg) intake valve angles to take advantage of the high lift flow. Port shape and sizing seems to favor all lift ranges. If a port change enhances high lift flow low lift flow is better also.---------Phil
Rick360 (Electrical) Apr 15, 2004
There are things that can help at certain lift ranges on some types of heads. What I would like to know is which is more important. Is it the highest .100" that matters most given equal port sizes, as I have calculated?
Rick
patprimmer (Automotive) Apr 15, 2004
I don't think it's that simple
It will depend a lot on cam profile, pressure gradient across the port to chamber interface and piston speed at the particular valve lift. This is I think a complex subject and variable from engine to engine.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
SMOKEY44211 (Automotive) Apr 16, 2004
If highest power is your primary consideration then I would have to say high lift flow is paramount. When the other factors of fuel economy, desire for broader torque curve, physical restrictions, rules restrictions enter into the equation then you are forced to look at both ends of the lift/flow curve. Every application has a different answer based on those variables.-----Phil
MaxRaceSoftware (Automotive) Apr 16, 2004
Rick360,
i use .87 % PerCent times the "Theoretical Cam's Max Lift"
then make sure i have great FlowBench CFM numbers from that point to ( .25 * Int_Valve_Diameter )....along without sacrificing too much flow at any other points below that range.
the .87 % => accounts for Valve Lash Loss, valvetrain deflection losses, some intake manifold and carb CFM loss,
and accounts for where the cam's "lift dwell time" would be most effective if you looked at Valve Lift / Piston Velocity / CFM demand
a .800" Lift cam - .025" Lash = .775"
.775" - another .025 to .030" valvetrain deflection loss
= .750" or so
.750" = valve lift is only at .750" a few degrees
.800" Lift times .87 % = .696" rounded off to .700" lift
cam will be at .700" lift to .500" lift when piston velocity is at maximum till cylinder volume is at maximum
its very important to have great Cyl Head Flow from
.25 * Int VD to between .37 to .41 times Int VD
Curtain_Area = Valve_Area when Valve Lift is .25 times Valve_Diameter
you still want Low-Lift flow to take maximum advantage of Inertia/Ram effects at Intake Valve closing point
and Intake Valve opening point...
but you want the Intake valve to act like a one-way valve
=> letting air flow into cylinder, but not letting air escape back out the cylinder
50,55,58 degree seat angles will help make intake valve seem like one-way valve...along with using a number of distinct valve seat angles ..instead of using a radius valve job on Intake side
on a few engine Dyno tests i did => Radius -vs- Angle
Intake valve jobs ....the "series of Angles" valve job on Intake side made Torque sooner in RPM curve and wider Torque Curve ..than the Radius Intake valve job...but both made close to same Peak HP
on older style cyl heads that have abrupt short turns
the Max_Useable_Valve_Lift = .37 * Intake_Valve_Diameter
on ProStock Technology;
the Max_Useable_Valve_Lift = .39 * Intake_Valve_Diameter
to
the Max_Useable_Valve_Lift = .41 * Intake_Valve_Diameter
anything greater seems to loose too much curtain area velocity without gaining enough CFM flow
.42 * Intake_Valve_Diameter would be the most Lift possible that would make Power
your Intake and Exhaust valve sizes should determine your Camshaft's max useable Lift in all out Race Engines !
to see if greater Intake Valve Lift would help ??
then just multiply ;
HP Potential Gain = .257 * CFM@28" * Number_of_Cylinders
.257
.285
.310 Factors
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
https://ls1tech.com/forums/generation-iii-internal-engine/223995-importance-mid-lift-flow-numbers.html
Anyhow, it references another thread.
http://www.eng-tips.com/viewthread.cfm?qid=92513
which has some good info from Larry Meaux of Meaux Racing Heads in Louisiana.
The references a thread which has info from Darin Morgan of Reher Morrison
http://speedtalk.com/forum/viewtopic.php?t=321
Here is some of the more important info...
http://www.eng-tips.com/viewthread.cfm?qid=92513
Rick360 (Electrical) Apr 14, 2004
When porting a set of heads there are ways to enhance high, mid or low lift flow characteristics. I realize the ideal is to gain at all lifts but sometimes there is a tradeoff.
Which one would you trade for what other one? and why?
I profiled a cam which has .800" net lift thru its entire lift curve to see how long the valve was at what point, the piston velocity, and the flow at that lift. I then calculated theoretical flows throughout the intake stroke to see which lift points made the bigger difference. It seems that .700" and up had a bigger effect. Does this hold true on a dyno? Would gaining 10cfm at .7" - .8" be worth giving up 10 cfm at .5"-.6"?
Rick
Start Your Own Eng-Tips Group! Click Here!
SMOKEY44211 (Automotive) Apr 15, 2004
I have found the biggest single factor affecting low, mid and high lift flow is the valve seat angle. Shallow angles (15-30deg)tend to favor low lift flow. In some racing classes where the cam may be lift restricted there is some gain to optimizing low lift flow. Current trend in Pro stock drag class seems to favor steep (55deg) intake valve angles to take advantage of the high lift flow. Port shape and sizing seems to favor all lift ranges. If a port change enhances high lift flow low lift flow is better also.---------Phil
Rick360 (Electrical) Apr 15, 2004
There are things that can help at certain lift ranges on some types of heads. What I would like to know is which is more important. Is it the highest .100" that matters most given equal port sizes, as I have calculated?
Rick
patprimmer (Automotive) Apr 15, 2004
I don't think it's that simple
It will depend a lot on cam profile, pressure gradient across the port to chamber interface and piston speed at the particular valve lift. This is I think a complex subject and variable from engine to engine.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
SMOKEY44211 (Automotive) Apr 16, 2004
If highest power is your primary consideration then I would have to say high lift flow is paramount. When the other factors of fuel economy, desire for broader torque curve, physical restrictions, rules restrictions enter into the equation then you are forced to look at both ends of the lift/flow curve. Every application has a different answer based on those variables.-----Phil
MaxRaceSoftware (Automotive) Apr 16, 2004
Rick360,
i use .87 % PerCent times the "Theoretical Cam's Max Lift"
then make sure i have great FlowBench CFM numbers from that point to ( .25 * Int_Valve_Diameter )....along without sacrificing too much flow at any other points below that range.
the .87 % => accounts for Valve Lash Loss, valvetrain deflection losses, some intake manifold and carb CFM loss,
and accounts for where the cam's "lift dwell time" would be most effective if you looked at Valve Lift / Piston Velocity / CFM demand
a .800" Lift cam - .025" Lash = .775"
.775" - another .025 to .030" valvetrain deflection loss
= .750" or so
.750" = valve lift is only at .750" a few degrees
.800" Lift times .87 % = .696" rounded off to .700" lift
cam will be at .700" lift to .500" lift when piston velocity is at maximum till cylinder volume is at maximum
its very important to have great Cyl Head Flow from
.25 * Int VD to between .37 to .41 times Int VD
Curtain_Area = Valve_Area when Valve Lift is .25 times Valve_Diameter
you still want Low-Lift flow to take maximum advantage of Inertia/Ram effects at Intake Valve closing point
and Intake Valve opening point...
but you want the Intake valve to act like a one-way valve
=> letting air flow into cylinder, but not letting air escape back out the cylinder
50,55,58 degree seat angles will help make intake valve seem like one-way valve...along with using a number of distinct valve seat angles ..instead of using a radius valve job on Intake side
on a few engine Dyno tests i did => Radius -vs- Angle
Intake valve jobs ....the "series of Angles" valve job on Intake side made Torque sooner in RPM curve and wider Torque Curve ..than the Radius Intake valve job...but both made close to same Peak HP
on older style cyl heads that have abrupt short turns
the Max_Useable_Valve_Lift = .37 * Intake_Valve_Diameter
on ProStock Technology;
the Max_Useable_Valve_Lift = .39 * Intake_Valve_Diameter
to
the Max_Useable_Valve_Lift = .41 * Intake_Valve_Diameter
anything greater seems to loose too much curtain area velocity without gaining enough CFM flow
.42 * Intake_Valve_Diameter would be the most Lift possible that would make Power
your Intake and Exhaust valve sizes should determine your Camshaft's max useable Lift in all out Race Engines !
to see if greater Intake Valve Lift would help ??
then just multiply ;
HP Potential Gain = .257 * CFM@28" * Number_of_Cylinders
.257
.285
.310 Factors
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
10-08-2004, 09:51 PM
#404
6600 rpm clutch dump of death Administrator
Thread Starter
LJW (Industrial) Apr 19, 2004
What a great thread!
What is the best strategy for dealing with very low lift/diameter ratios (.428 total lift/1.570 Intake Valve diameter)? Are tricks to limit reversion helpful in engines that do not have a lot of overlap?
Larry Wiechman
MaxRaceSoftware (Automotive) Apr 20, 2004
(.428 total lift/1.570 Intake Valve diameter)
============================================
equals = .2726 Lift/Diameter Ratio
its above the .25 L/D Ratio ...so might watchout for effects of BackCut angle on the intake valve -VS- no BackCut angle on intake valve ....just depends on how you port the bowl-area , short-turn, and valve job.
a 1.570 Intake Valve , using a safe .87 Factor times OD
will give you 1.837 sq. inches of cross-sectional area
that you shouldn't exceed if you want good port velocity
Cross-sectional area = 1.570 * .87 * 3.1416 * .428
if you had no overlap period...the engine would still respond to low-lift flow and valve job specs
because of Inertia Ram/Wave tuning effects at intake valve closing point
you could use .87 , .89, .90, .91 to (.92 as absolute max)
Factor ....this Factor accounts for the fact that the actual diameter at seat insert is much less than the valve's OD because of seat angle widths and number of seat angles, and transition into bowl and short-turn.
same way with effective valve area calculation
you have to also account for the valve stem dia.
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 23, 2004
Larry,
I have a simular problem, .. and have several questions for you, ..
but I'll start with a description of my project.
Round port, 3" long, 1.24" round at gasket tapering to 1.34" at the short turn or entry into the valve bowl.
The valve bowl is 1.40", throat under valve is 1.290" and the OD of the valve is 1.54"
spec cam has a max lift of .348" at the valve.
So, .. low lift flow is all I have to go after and the flow number that seems to transfer to the dyno & race track is .250" to .300"
I've been able to get 94 cfm @ 10" h2o at .350" lift.
So my questions, .. first your overall thoughts on the port size and their effects on the flow at .300" VS .200"
Second, .. I have been a "hands on" cylinder head guy for most of my life, ,,
and lack the math knowledge without the use of computers. Tips on getting the basics for a guy like me, . . . teach an old dog to be an engineer?
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Aug 25, 2004
.226 Lift/Diameter Ratio = (.348 / 1.540)
so its below the .25 L/D Ratio Valve-to-Port transition point, that means the valve job and Bowl-Area is mostly controlling all the Flow characteristics.
don't make the Cross-sectional area larger than 1.490 sq.in
and probably smaller than 1.200 is too small unless you are turning this engine at very low RPMs ?
Valve-----Curtain(effective)
Lift------Area
.200------0.714 sq.inches
.300------1.071
.348------1.242
.400------1.428
94 cfm @10" = 157.3 cfm @ 28 inches
1.540 od = 1.863 area = 84.4 cfm/sq.inch ratio @ 28"
----HP per Cylinder (28")-----(600 Rpm/Sec Dyno Rate)----
.257 Flow Factor = 40.4 HP potential per Cylinder
.285 Flow Factor = 44.8 for very good SuperStock engines
.300 Flow Factor = 47.2 for 16:1 CR State-of-Art ProStock
1.290 / 1.540 = 83.8 % ..sort of small ...should be able to effectively use 87 to 90 PerCent at the throat or seat insert area
87+ % percent should work better ??
------Velocity in Feet per Second-----(.350" Lift & 28")
1.240 area at gasket = 312.6 fps
1.410 area at valve bowl = 267.7 fps
1.307 area at throat = 288.9 fps
312.6 fps is about the highest velocity you would want to see inside your Port at the smallest cross-sectional area when flow tested at 28 inches ...anything too much higher than that will be on the verge of loosing HP ..you sure won't be able to push it past 350 fps at 28 inches
at 10 inches = 209.3 fps is too high
at 28 inches = 350.3 fps is too high
at 36 inches = 397.2 fps is too high
even though you see Flow gains on the Bench it will begin not to correlate into real world HP past 350 fps port velocity at 28 inches or 209.3 fps @ 10 inches...in fact if you make the head flow more with a Sonic Choke problem..you'll just make the head go sooner into Sonic Choke on a live engine
at 350 fps at 28 inches you might only see a few HP loss, but as go go past that point...HP drops like a rock as Sonic Choke sets in earlier in the Lift Cycle
Example=> small Block Chevy engine 570 HP 165 cc port volume 1.940/1.500 valves 375 fps port velocity max @ 36 inches on FlowBench with 36 " Test Pressure
2 different pairs of the same exact casting number/valve sizes/port volumes/etc. ..even have identical flow numbers on intake and exhaust sides (just different port shapes)
1 pair has 458.6 fps port velocity at 36 inches
and looses over 75 HP at 7500 RPM compared to the other identical pair of heads that had 375 fps port velocity
if you add more max lift with a head like this, you just go into Sonic Choke earlier..thats why some engines don't respond to cam/valve lift increases.
if your engine doesn't like at least .37 Lift/Diameter Ratio then you have a severe Sonic Choke/Flow restriction problem
if rules allow , on the Intake side an engine should like .37 to .42+ L/D Ratio on max effort type engines
if port axis to valve axis is severe..heads might only respond up to .37-.39 L/D Ratio..as short turn radius gets better and port-to-valve axis gets better, then engine should respond towards .41-.42+ L/D Ratios on the Intake side
the Exhaust L/D Ratio is usually 95+ PerCent of the Intake side
in all out max-effort engine =
your valve sizes should ultimately determine cam's max lift
your desired engine operating RPM range should determine
overlap period and durations
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 27, 2004
Larry,
A few questions, .. the curtain area at .300" how much will that flow?
what's the best possable?
also, .. I'm very bad at math, .. is there a spread sheet available to do the calc's, .. curtian area, .. etc.?
About the "sonic choke" these Velocities you referr to, .. how does that translate to the running engine, .. as the dynamic velocities must be much higher.
This is a restricted engine, .. stock cam, Webber 2bl. carb, .. 9.5:1 comp.
we turn them about 7000 max, .. peak HP tendes to be around 6200.
A more complex problem, and one you have made a refference to.
Just ran a track test a few weeks ago, .. ran a baseline, .. then swapped on my head, car went a second a lap faster on a 2.6 mi road course.
Huge gain, and the driver said he could feel the difference.
That engine got pulled and went to builder "A", ran back to back dyno on the two heads, .. showed less then 1/2 hp difference, .. and the TQ and HP curves where the same.
The faster head from the track test them came to a test in MD, .. rebuilt shortblock, .. and a back to back with my head and the customer's best head, .. less then 1/2 hp difference. The only difference I could find is the BSFC on my head was 2-3 points higher, .. with the same 1280 a/f setting.
But we know it's faster on the track, .. customer could feel the difference, .. and the lap time didn't lie, . I was at the test.
So, .. what's the deal????? If the car goes faster but we can't measure the difference on the dyno it has to be acceleration rate, .. but a second a lap? Now we tested at Watkins Glen, .. known as a HP track.
Your thoughts, .. is there a way to measure this.
With this combo this has been happining often, .. seeing no real gain over another ported head on the dyno but they run great on the track??????
Thanks,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
What a great thread!
What is the best strategy for dealing with very low lift/diameter ratios (.428 total lift/1.570 Intake Valve diameter)? Are tricks to limit reversion helpful in engines that do not have a lot of overlap?
Larry Wiechman
MaxRaceSoftware (Automotive) Apr 20, 2004
(.428 total lift/1.570 Intake Valve diameter)
============================================
equals = .2726 Lift/Diameter Ratio
its above the .25 L/D Ratio ...so might watchout for effects of BackCut angle on the intake valve -VS- no BackCut angle on intake valve ....just depends on how you port the bowl-area , short-turn, and valve job.
a 1.570 Intake Valve , using a safe .87 Factor times OD
will give you 1.837 sq. inches of cross-sectional area
that you shouldn't exceed if you want good port velocity
Cross-sectional area = 1.570 * .87 * 3.1416 * .428
if you had no overlap period...the engine would still respond to low-lift flow and valve job specs
because of Inertia Ram/Wave tuning effects at intake valve closing point
you could use .87 , .89, .90, .91 to (.92 as absolute max)
Factor ....this Factor accounts for the fact that the actual diameter at seat insert is much less than the valve's OD because of seat angle widths and number of seat angles, and transition into bowl and short-turn.
same way with effective valve area calculation
you have to also account for the valve stem dia.
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 23, 2004
Larry,
I have a simular problem, .. and have several questions for you, ..
but I'll start with a description of my project.
Round port, 3" long, 1.24" round at gasket tapering to 1.34" at the short turn or entry into the valve bowl.
The valve bowl is 1.40", throat under valve is 1.290" and the OD of the valve is 1.54"
spec cam has a max lift of .348" at the valve.
So, .. low lift flow is all I have to go after and the flow number that seems to transfer to the dyno & race track is .250" to .300"
I've been able to get 94 cfm @ 10" h2o at .350" lift.
So my questions, .. first your overall thoughts on the port size and their effects on the flow at .300" VS .200"
Second, .. I have been a "hands on" cylinder head guy for most of my life, ,,
and lack the math knowledge without the use of computers. Tips on getting the basics for a guy like me, . . . teach an old dog to be an engineer?
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Aug 25, 2004
.226 Lift/Diameter Ratio = (.348 / 1.540)
so its below the .25 L/D Ratio Valve-to-Port transition point, that means the valve job and Bowl-Area is mostly controlling all the Flow characteristics.
don't make the Cross-sectional area larger than 1.490 sq.in
and probably smaller than 1.200 is too small unless you are turning this engine at very low RPMs ?
Valve-----Curtain(effective)
Lift------Area
.200------0.714 sq.inches
.300------1.071
.348------1.242
.400------1.428
94 cfm @10" = 157.3 cfm @ 28 inches
1.540 od = 1.863 area = 84.4 cfm/sq.inch ratio @ 28"
----HP per Cylinder (28")-----(600 Rpm/Sec Dyno Rate)----
.257 Flow Factor = 40.4 HP potential per Cylinder
.285 Flow Factor = 44.8 for very good SuperStock engines
.300 Flow Factor = 47.2 for 16:1 CR State-of-Art ProStock
1.290 / 1.540 = 83.8 % ..sort of small ...should be able to effectively use 87 to 90 PerCent at the throat or seat insert area
87+ % percent should work better ??
------Velocity in Feet per Second-----(.350" Lift & 28")
1.240 area at gasket = 312.6 fps
1.410 area at valve bowl = 267.7 fps
1.307 area at throat = 288.9 fps
312.6 fps is about the highest velocity you would want to see inside your Port at the smallest cross-sectional area when flow tested at 28 inches ...anything too much higher than that will be on the verge of loosing HP ..you sure won't be able to push it past 350 fps at 28 inches
at 10 inches = 209.3 fps is too high
at 28 inches = 350.3 fps is too high
at 36 inches = 397.2 fps is too high
even though you see Flow gains on the Bench it will begin not to correlate into real world HP past 350 fps port velocity at 28 inches or 209.3 fps @ 10 inches...in fact if you make the head flow more with a Sonic Choke problem..you'll just make the head go sooner into Sonic Choke on a live engine
at 350 fps at 28 inches you might only see a few HP loss, but as go go past that point...HP drops like a rock as Sonic Choke sets in earlier in the Lift Cycle
Example=> small Block Chevy engine 570 HP 165 cc port volume 1.940/1.500 valves 375 fps port velocity max @ 36 inches on FlowBench with 36 " Test Pressure
2 different pairs of the same exact casting number/valve sizes/port volumes/etc. ..even have identical flow numbers on intake and exhaust sides (just different port shapes)
1 pair has 458.6 fps port velocity at 36 inches
and looses over 75 HP at 7500 RPM compared to the other identical pair of heads that had 375 fps port velocity
if you add more max lift with a head like this, you just go into Sonic Choke earlier..thats why some engines don't respond to cam/valve lift increases.
if your engine doesn't like at least .37 Lift/Diameter Ratio then you have a severe Sonic Choke/Flow restriction problem
if rules allow , on the Intake side an engine should like .37 to .42+ L/D Ratio on max effort type engines
if port axis to valve axis is severe..heads might only respond up to .37-.39 L/D Ratio..as short turn radius gets better and port-to-valve axis gets better, then engine should respond towards .41-.42+ L/D Ratios on the Intake side
the Exhaust L/D Ratio is usually 95+ PerCent of the Intake side
in all out max-effort engine =
your valve sizes should ultimately determine cam's max lift
your desired engine operating RPM range should determine
overlap period and durations
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 27, 2004
Larry,
A few questions, .. the curtain area at .300" how much will that flow?
what's the best possable?
also, .. I'm very bad at math, .. is there a spread sheet available to do the calc's, .. curtian area, .. etc.?
About the "sonic choke" these Velocities you referr to, .. how does that translate to the running engine, .. as the dynamic velocities must be much higher.
This is a restricted engine, .. stock cam, Webber 2bl. carb, .. 9.5:1 comp.
we turn them about 7000 max, .. peak HP tendes to be around 6200.
A more complex problem, and one you have made a refference to.
Just ran a track test a few weeks ago, .. ran a baseline, .. then swapped on my head, car went a second a lap faster on a 2.6 mi road course.
Huge gain, and the driver said he could feel the difference.
That engine got pulled and went to builder "A", ran back to back dyno on the two heads, .. showed less then 1/2 hp difference, .. and the TQ and HP curves where the same.
The faster head from the track test them came to a test in MD, .. rebuilt shortblock, .. and a back to back with my head and the customer's best head, .. less then 1/2 hp difference. The only difference I could find is the BSFC on my head was 2-3 points higher, .. with the same 1280 a/f setting.
But we know it's faster on the track, .. customer could feel the difference, .. and the lap time didn't lie, . I was at the test.
So, .. what's the deal????? If the car goes faster but we can't measure the difference on the dyno it has to be acceleration rate, .. but a second a lap? Now we tested at Watkins Glen, .. known as a HP track.
Your thoughts, .. is there a way to measure this.
With this combo this has been happining often, .. seeing no real gain over another ported head on the dyno but they run great on the track??????
Thanks,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
10-08-2004, 09:53 PM
#405
6600 rpm clutch dump of death Administrator
Thread Starter
MaxRaceSoftware (Automotive) Aug 27, 2004
A few questions, .. the curtain area at .300" how much will that flow?
what's the best possable?
also, .. I'm very bad at math, .. is there a spread sheet available to do the calc's, .. curtian area, .. etc.?
--------------------------------
theoretical flow at .300" lift should be = 93.4 cfm @ 10"
10 inches of Flow Test Pressure =>209.3 fps
209.343 fps = (10 ^ .5) * 66.2
where 10= Test Pressure & 66.2 = Units Constant , ^.5= SquareRoot
then CFM = FPS * Area * .41666667
so 93.4 CFM = 209.343 fps * 1.071 * .41666667
where 1.071 is the Effective Curtain Area @ .300" Lift
and i'm calculating all this stuff on a handheld calculator & posting from my Home Computer..all my Formulas/Equations/Software are on my Shop Computer so i maybe off a few thousandths at .300" Lift for your Effective Curtain Area... i already noticed a few math errors in my previous Post
------Velocity in Feet per Second-----(.350" Lift & 28")
1.240 area at gasket = 312.6 fps
1.410 area at valve bowl = 267.7 fps
1.307 area at throat = 288.9 fps
should read this instead
------Velocity in Feet per Second-----(.350" Lift & 28")
1.208 area at gasket = 312.5 fps
1.410 area at Short Turn = 267.8 fps
1.540 area at valve bowl = 245.1 fps
1.307 area at throat = 288.9 fps
<<<About the "sonic choke" these Velocities you referr to, .. how does that translate to the running engine, .. as the dynamic velocities must be much higher.<<<
10 inches of Flow Test Pressure =>209.3 fps
209.343 fps = (10 ^ .5) * 66.2
where 10= Test Pressure & 66.2 = Units Constant , ^.5= SquareRoot
you are Flow testing at 10 inches of Test Pressure , so if
you see 10 inches "or more" of Pitot Probe pressure, then
you are close to starting point where that 209.343 fps on the FlowBench will begin to correlate into Sonic Choke in live engine condition 600 to 700 fps (82.2 to 111.8 inches) Same thing at 28" or any test pressure...if your Pitot Probe pressure reading at the smallest cross-sectional area is equal to or greater than your test pressure the FlowBench will begin not to correlate to real HP
<<<The faster head from the track test them came to a test in MD, .. rebuilt shortblock, .. and a back to back with my head and the customer's best head, .. less then 1/2 hp difference. The only difference I could find is the BSFC on my head was 2-3 points higher, .. with the same 1280 a/f setting.
But we know it's faster on the track, .. customer could feel the difference, .. and the lap time didn't lie, . I was at the test.<<<<
take some Pitot Probe readings as you Flow Test your heads
use a 180 deg or "J" type Probe on the Intake side
you want to measure velocity fps...see what you come up with between the 2 Heads
Plenum volume or entire Induction volume can cause differences between Track and Dyno
the engine with higher BSFC's usually runs slower down the DragStrip compared to what Dyno might show
how much different is the Engine Rpm/Sec accel rate on the Road Course compared to on the Dyno ??
Dyno headers & Dyno exh lengths/mufflers -vs- in Car exhaust, can change how much HP engine makes in the Car
one Head might like the Dyno exhaust and make 200 HP
the other Head might not like the Dyno exh but still make 200 HP, but more in the Car with real headers/exh system
an onboard Data Recorder also linked to Strain Gauge setup on driveshaft yoke would reveal a lot of useful info .
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 27, 2004
I didn't mean to hi-jack Rick's thread here, .. Rick are you OK with this?
Larry,
Thanks for the time you take to discuss this, ..
The FASTER head had 2-3 higher BSFC on the dyno at 1280 a/f.
I think the dyno headers are the same as what we used in the car, ..
I know port volume on the faster head is a few cc's larger, . . .
The kicker to this is, .. this has been happining with all the engine builders I supply. Dyno numbers don't look that different but the on-track performence is much better. Four different dynos, .. four different engine builders, .. same engine package.
Thanks for the math lesson on the curtain area & flow. I need some serious work on my math skills.
By your calc, .. I'm getting all that the curtain area will flow, .. around 93 cfm @ 10", .. My new flow bench being built will flow 900 cfm @ 36", .. I'm going to try some tests at 36" to see if a difference shows up.
Another thing to throw in the mix, .. and maybe the reason why the BSFC is up. With the limited cam we retard the stock cam to get the engine to run up high. I took the exhaust port and made it flow 100% of the intake at .050" up to .200", .. the idea was to help scavenge the cylinder and help the cam.
The real problem is I have one engine builder that seems to "challenge" me on this. If it doesn't run better on the dyno it "can't" be better on the track?
Thanks,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Aug 27, 2004
>> My new flow bench being built will flow 900 cfm @ 36", .. I'm going to try some tests at 36" to see if a difference shows up.<<
tryout 50" to 60" Test Pressure also and see if theres a difference ??
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
GT6Steve (Industrial) Aug 27, 2004
Larry says "an onboard Data Recorder also linked to Strain Gauge setup on driveshaft yoke would reveal a lot of useful info".
Forgive me changing the subject but this sounds like an onboard dyno. Can you elaborate on the strain gage setup?
Steve
MaxRaceSoftware (Automotive) Aug 27, 2004
>>the Exhaust L/D Ratio is usually 95+ PerCent of the Intake side<<
the above is wrong, it should have read =>
the Exhaust Valve Lift is usually 95+ PerCent of the Intake Side
================================================
Forgive me changing the subject but this sounds like an onboard dyno. Can you elaborate on the strain gage setup?
---Steve
http://www.land-and-sea.com/rotary-s...shaft-dyno.htm
Steve checkout the above Link ... there are more articles on this elsewhere .
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
A few questions, .. the curtain area at .300" how much will that flow?
what's the best possable?
also, .. I'm very bad at math, .. is there a spread sheet available to do the calc's, .. curtian area, .. etc.?
--------------------------------
theoretical flow at .300" lift should be = 93.4 cfm @ 10"
10 inches of Flow Test Pressure =>209.3 fps
209.343 fps = (10 ^ .5) * 66.2
where 10= Test Pressure & 66.2 = Units Constant , ^.5= SquareRoot
then CFM = FPS * Area * .41666667
so 93.4 CFM = 209.343 fps * 1.071 * .41666667
where 1.071 is the Effective Curtain Area @ .300" Lift
and i'm calculating all this stuff on a handheld calculator & posting from my Home Computer..all my Formulas/Equations/Software are on my Shop Computer so i maybe off a few thousandths at .300" Lift for your Effective Curtain Area... i already noticed a few math errors in my previous Post
------Velocity in Feet per Second-----(.350" Lift & 28")
1.240 area at gasket = 312.6 fps
1.410 area at valve bowl = 267.7 fps
1.307 area at throat = 288.9 fps
should read this instead
------Velocity in Feet per Second-----(.350" Lift & 28")
1.208 area at gasket = 312.5 fps
1.410 area at Short Turn = 267.8 fps
1.540 area at valve bowl = 245.1 fps
1.307 area at throat = 288.9 fps
<<<About the "sonic choke" these Velocities you referr to, .. how does that translate to the running engine, .. as the dynamic velocities must be much higher.<<<
10 inches of Flow Test Pressure =>209.3 fps
209.343 fps = (10 ^ .5) * 66.2
where 10= Test Pressure & 66.2 = Units Constant , ^.5= SquareRoot
you are Flow testing at 10 inches of Test Pressure , so if
you see 10 inches "or more" of Pitot Probe pressure, then
you are close to starting point where that 209.343 fps on the FlowBench will begin to correlate into Sonic Choke in live engine condition 600 to 700 fps (82.2 to 111.8 inches) Same thing at 28" or any test pressure...if your Pitot Probe pressure reading at the smallest cross-sectional area is equal to or greater than your test pressure the FlowBench will begin not to correlate to real HP
<<<The faster head from the track test them came to a test in MD, .. rebuilt shortblock, .. and a back to back with my head and the customer's best head, .. less then 1/2 hp difference. The only difference I could find is the BSFC on my head was 2-3 points higher, .. with the same 1280 a/f setting.
But we know it's faster on the track, .. customer could feel the difference, .. and the lap time didn't lie, . I was at the test.<<<<
take some Pitot Probe readings as you Flow Test your heads
use a 180 deg or "J" type Probe on the Intake side
you want to measure velocity fps...see what you come up with between the 2 Heads
Plenum volume or entire Induction volume can cause differences between Track and Dyno
the engine with higher BSFC's usually runs slower down the DragStrip compared to what Dyno might show
how much different is the Engine Rpm/Sec accel rate on the Road Course compared to on the Dyno ??
Dyno headers & Dyno exh lengths/mufflers -vs- in Car exhaust, can change how much HP engine makes in the Car
one Head might like the Dyno exhaust and make 200 HP
the other Head might not like the Dyno exh but still make 200 HP, but more in the Car with real headers/exh system
an onboard Data Recorder also linked to Strain Gauge setup on driveshaft yoke would reveal a lot of useful info .
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 27, 2004
I didn't mean to hi-jack Rick's thread here, .. Rick are you OK with this?
Larry,
Thanks for the time you take to discuss this, ..
The FASTER head had 2-3 higher BSFC on the dyno at 1280 a/f.
I think the dyno headers are the same as what we used in the car, ..
I know port volume on the faster head is a few cc's larger, . . .
The kicker to this is, .. this has been happining with all the engine builders I supply. Dyno numbers don't look that different but the on-track performence is much better. Four different dynos, .. four different engine builders, .. same engine package.
Thanks for the math lesson on the curtain area & flow. I need some serious work on my math skills.
By your calc, .. I'm getting all that the curtain area will flow, .. around 93 cfm @ 10", .. My new flow bench being built will flow 900 cfm @ 36", .. I'm going to try some tests at 36" to see if a difference shows up.
Another thing to throw in the mix, .. and maybe the reason why the BSFC is up. With the limited cam we retard the stock cam to get the engine to run up high. I took the exhaust port and made it flow 100% of the intake at .050" up to .200", .. the idea was to help scavenge the cylinder and help the cam.
The real problem is I have one engine builder that seems to "challenge" me on this. If it doesn't run better on the dyno it "can't" be better on the track?
Thanks,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Aug 27, 2004
>> My new flow bench being built will flow 900 cfm @ 36", .. I'm going to try some tests at 36" to see if a difference shows up.<<
tryout 50" to 60" Test Pressure also and see if theres a difference ??
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
GT6Steve (Industrial) Aug 27, 2004
Larry says "an onboard Data Recorder also linked to Strain Gauge setup on driveshaft yoke would reveal a lot of useful info".
Forgive me changing the subject but this sounds like an onboard dyno. Can you elaborate on the strain gage setup?
Steve
MaxRaceSoftware (Automotive) Aug 27, 2004
>>the Exhaust L/D Ratio is usually 95+ PerCent of the Intake side<<
the above is wrong, it should have read =>
the Exhaust Valve Lift is usually 95+ PerCent of the Intake Side
================================================
Forgive me changing the subject but this sounds like an onboard dyno. Can you elaborate on the strain gage setup?
---Steve
http://www.land-and-sea.com/rotary-s...shaft-dyno.htm
Steve checkout the above Link ... there are more articles on this elsewhere .
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
10-08-2004, 09:53 PM
#406
6600 rpm clutch dump of death Administrator
Thread Starter
CurtisBoggs (Automotive) Aug 29, 2004
Larry,
Did some flow tests at higher pressures, .. didn't find anything significant. My exhaust port does flow better at low lifts though.
The only thing I haven't done is wet flow tests, .. .. so I'm guessing
that my valve job VS the other valve job has better wet flow.
Since you've seen identical engines on the dyno run different on the track, .. have you been able to trace it back to why???
Thanks,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
CurtisBoggs (Automotive) Aug 29, 2004
seat angle?
any experience with a 30º or 35º seat angle, ..
do they live, .. how long etc. ????
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Aug 29, 2004
Since you've seen identical engines on the dyno run different on the track, .. have you been able to trace it back to why???--Thanks,--Curtis
---------------------------------
So far on my SF-901 Dyno the Engines run what they should down the DragStrip,...but i've heard a few Stories like your's .
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
MaxRaceSoftware (Automotive) Aug 29, 2004
seat angle?
any experience with a 30º or 35º seat angle, ..
do they live, .. how long etc. ????
Curtis
--------------------
Pontiac and Oldsmobile used 30 deg seat/valve angles on a few OEM engines...i use to convert some these 30 deg to 45 angles for ET Bracket racing but that was with .450" lift cams and upwards
a 1.540 valve w/max .348" Lift would probably like a 30 or 35 deg VJ might be better..thats where you can experiment
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 29, 2004
Larry,
Thanks, .. yes I'm going to try a 30, 35 & 37, .. see what happens.
Thanks again,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Sep 9, 2004
A few questions, .. the curtain area at .300" how much will that flow?
what's the best possable?
also, .. I'm very bad at math, .. is there a spread sheet available to do the calc's, .. curtian area, .. etc.?
================================================== =
Curtis, Darin Morgan has a Excel SpreadSheet available
for you to download and use or at least get an idea of whats important/relevant ?
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at
http://www.rehermorrison.com
Go to my (Darin's) web site at
http://webpages.charter.net/dsda/
I have uploaded an XL spread sheet showing the discharge Coe.
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Sep 9, 2004
Larry,
Thanks, .. you ARE the MAN!
Another question, .. perhaps for another thread, ..
I'm thinking about building a F/ED dragester with a Mopar W9 rp cylinder head on a Mopar aluminum 4 cylinder block, ..
do you have any experience with these combos?
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
Rick360 (Electrical) Sep 9, 2004
Larry,
Thanks for the info. I checked out the spreadsheet to see the formulas involved and I have a question about the disch coef. The basic formula is FLOW/(CURTAIN AREA * 137.7). What is 137.7 for? a constant for something? Is this constant different depending on test pressure?
Rick
MaxRaceSoftware (Automotive) Sep 10, 2004
Larry,
Thanks for the info. I checked out the spreadsheet to see the formulas involved and I have a question about the disch coef. The basic formula is FLOW/(CURTAIN AREA * 137.7). What is 137.7 for? a constant for something? Is this constant different depending on test pressure?--Rick
-------------------------------------------------
Quote by Darin Morgan =>
"There are many coefficients that I use and CFM/SQin is by far the simplest. The other coefficients you should learn and use are,
(1) Discharge Coe. Based on theoretical maximum such as the SAE factor of 137CFM/SQin or the 146CFM/SQin that most of us use. The equation uses the window area at every lift increment, the theoretical maximum and a ratio of effective area and actual flow area."
Rick for more Info checkout this Link
http://speedtalk.com/forum/viewtopic.php?t=321
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
http://www.maxracesoftware.com/
CurtisBoggs (Automotive) Sep 11, 2004
Larry,
More discussions, ..
I have a 2" valve, .. data from my portflow software.
.200" lift, 132.6 cfm @ 28" , est valve area 1.257, 105 cfm per sq in.,
flow area sq in. .910, flow coef. .724
.300" lift, 201.1 cfm, est valve area sq in. 1885, 106.67 cfm per sq in.,
flow area sq in. 1.380, flow coef. .732
So, am I missing something or does this seem to be fairly poor??
This is a late model 5.7 Hemi head, .. ported, valve job with wide 60 still using the 45, and flow didn't chamge at all under .400" ????????????
I've gained nothing in the lift range of the cam, ..Help!
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
Larry,
Did some flow tests at higher pressures, .. didn't find anything significant. My exhaust port does flow better at low lifts though.
The only thing I haven't done is wet flow tests, .. .. so I'm guessing
that my valve job VS the other valve job has better wet flow.
Since you've seen identical engines on the dyno run different on the track, .. have you been able to trace it back to why???
Thanks,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
CurtisBoggs (Automotive) Aug 29, 2004
seat angle?
any experience with a 30º or 35º seat angle, ..
do they live, .. how long etc. ????
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Aug 29, 2004
Since you've seen identical engines on the dyno run different on the track, .. have you been able to trace it back to why???--Thanks,--Curtis
---------------------------------
So far on my SF-901 Dyno the Engines run what they should down the DragStrip,...but i've heard a few Stories like your's .
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
MaxRaceSoftware (Automotive) Aug 29, 2004
seat angle?
any experience with a 30º or 35º seat angle, ..
do they live, .. how long etc. ????
Curtis
--------------------
Pontiac and Oldsmobile used 30 deg seat/valve angles on a few OEM engines...i use to convert some these 30 deg to 45 angles for ET Bracket racing but that was with .450" lift cams and upwards
a 1.540 valve w/max .348" Lift would probably like a 30 or 35 deg VJ might be better..thats where you can experiment
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Aug 29, 2004
Larry,
Thanks, .. yes I'm going to try a 30, 35 & 37, .. see what happens.
Thanks again,
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
MaxRaceSoftware (Automotive) Sep 9, 2004
A few questions, .. the curtain area at .300" how much will that flow?
what's the best possable?
also, .. I'm very bad at math, .. is there a spread sheet available to do the calc's, .. curtian area, .. etc.?
================================================== =
Curtis, Darin Morgan has a Excel SpreadSheet available
for you to download and use or at least get an idea of whats important/relevant ?
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at
http://www.rehermorrison.com
Go to my (Darin's) web site at
http://webpages.charter.net/dsda/
I have uploaded an XL spread sheet showing the discharge Coe.
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
CurtisBoggs (Automotive) Sep 9, 2004
Larry,
Thanks, .. you ARE the MAN!
Another question, .. perhaps for another thread, ..
I'm thinking about building a F/ED dragester with a Mopar W9 rp cylinder head on a Mopar aluminum 4 cylinder block, ..
do you have any experience with these combos?
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
Rick360 (Electrical) Sep 9, 2004
Larry,
Thanks for the info. I checked out the spreadsheet to see the formulas involved and I have a question about the disch coef. The basic formula is FLOW/(CURTAIN AREA * 137.7). What is 137.7 for? a constant for something? Is this constant different depending on test pressure?
Rick
MaxRaceSoftware (Automotive) Sep 10, 2004
Larry,
Thanks for the info. I checked out the spreadsheet to see the formulas involved and I have a question about the disch coef. The basic formula is FLOW/(CURTAIN AREA * 137.7). What is 137.7 for? a constant for something? Is this constant different depending on test pressure?--Rick
-------------------------------------------------
Quote by Darin Morgan =>
"There are many coefficients that I use and CFM/SQin is by far the simplest. The other coefficients you should learn and use are,
(1) Discharge Coe. Based on theoretical maximum such as the SAE factor of 137CFM/SQin or the 146CFM/SQin that most of us use. The equation uses the window area at every lift increment, the theoretical maximum and a ratio of effective area and actual flow area."
Rick for more Info checkout this Link
http://speedtalk.com/forum/viewtopic.php?t=321
Larry Meaux (maxracesoftware@yahoo.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers
Support Israel - Genesis 12:3
http://www.maxracesoftware.com/
CurtisBoggs (Automotive) Sep 11, 2004
Larry,
More discussions, ..
I have a 2" valve, .. data from my portflow software.
.200" lift, 132.6 cfm @ 28" , est valve area 1.257, 105 cfm per sq in.,
flow area sq in. .910, flow coef. .724
.300" lift, 201.1 cfm, est valve area sq in. 1885, 106.67 cfm per sq in.,
flow area sq in. 1.380, flow coef. .732
So, am I missing something or does this seem to be fairly poor??
This is a late model 5.7 Hemi head, .. ported, valve job with wide 60 still using the 45, and flow didn't chamge at all under .400" ????????????
I've gained nothing in the lift range of the cam, ..Help!
Curtis
Curtis Boggs
Racing Flow Development
http://www.raceflowdevelopment.com
10-08-2004, 09:55 PM
#407
6600 rpm clutch dump of death Administrator
Thread Starter
http://speedtalk.com/forum/viewtopic.php?t=321
bill jones
New Member
Joined: 05 Sep 2004
Posts: 37
Location: salt lake city, ut
Posted: Tue Sep 07, 2004 5:06 pm Post subject: Darin's 116cfm per square is measured using what criteria?
--------------------------------------------------------------------------------
-Darrin Morgan mentioned 116cfm per square inch of port area as being a pretty important number to him at .900" lift
-Could I get an explanation of how this 116 is determined and why that number is so important.
-It appears to me that this 116CFM number probably changes with application like for a low lift 4 valve per cylinder engine or a .500" lift two valve per cylinder street engine what should we be looking for?
-I would think this 116CFM number has to be based on a certain test pressure used on a flowbench like probably at 28", so if you had flow numbers at 25" you'd have about a 5.8% lower number like 109CFM per square inch?
-What is considered excellent cfm per square inch at the lower valve lift increments?
-Is this 116 number based on valve diameter, throat diameter, average port crossectional area, used only for the intake or also includes the exhaust port?
-Is it figured with an intake manifold and/or carburetors installed?
----------------------------------
-I have a lot of porting and flowtesting experience with everything except .900" lift flow numbers, doing mostly lower budget oval track and bracket racer projects and the past 5 years or so a lot of 4 valve projects that only have .350" to .400" max valve lift.
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bill jones
New Member
Joined: 05 Sep 2004
Posts: 37
Location: salt lake city, ut
Posted: Tue Sep 07, 2004 5:06 pm Post subject: Darin's 116cfm per square is measured using what criteria?
--------------------------------------------------------------------------------
-Darrin Morgan mentioned 116cfm per square inch of port area as being a pretty important number to him at .900" lift
-Could I get an explanation of how this 116 is determined and why that number is so important.
-It appears to me that this 116CFM number probably changes with application like for a low lift 4 valve per cylinder engine or a .500" lift two valve per cylinder street engine what should we be looking for?
-I would think this 116CFM number has to be based on a certain test pressure used on a flowbench like probably at 28", so if you had flow numbers at 25" you'd have about a 5.8% lower number like 109CFM per square inch?
-What is considered excellent cfm per square inch at the lower valve lift increments?
-Is this 116 number based on valve diameter, throat diameter, average port crossectional area, used only for the intake or also includes the exhaust port?
-Is it figured with an intake manifold and/or carburetors installed?
----------------------------------
-I have a lot of porting and flowtesting experience with everything except .900" lift flow numbers, doing mostly lower budget oval track and bracket racer projects and the past 5 years or so a lot of 4 valve projects that only have .350" to .400" max valve lift.
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10-08-2004, 09:56 PM
#408
6600 rpm clutch dump of death Administrator
Thread Starter
shawn
New Member
Joined: 11 Aug 2003
Posts: 28
Posted: Tue Sep 07, 2004 6:03 pm Post subject:
--------------------------------------------------------------------------------
I think he is refering to flow vs. valve diameter at the standard 28"'s, with a specific type of valve job. This would put a 2.500 inch at about 569 cfm.Is this right Darin?I think this is also a threshold that the headporters strive for.With a given bore diameter and engine combo, the intake valve diameter is limited. It's up to the smart guys like Darin to squeeze as much flow as possible out of this as possible and still have something that will accelerate down the track. How did I do Darin?
Shawn
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Darin Morgan
Guest
Posted: Wed Sep 08, 2004 7:32 am Post subject: Coe
--------------------------------------------------------------------------------
This subject is far to complex to get into on a message board because a small book can be written on this subject alone. If you do heads for living you need to study and understand flow coefficients and discharge coefficients as well as the proper use of ratios. Without a thorough understanding of these concepts you will not be able to design the most efficient port possible for a given engine combination. Raw flow figures are Satan's tool of deception! I don't mean to get to dramatic but that pretty much sums up my view about people who use flow figures to rate a cylinder heads efficiency. There are many coefficients that I use and CFM/SQin is by far the simplest. The other coefficients you should learn and use are,
(1) Discharge Coe. Based on theoretical maximum such as the SAE factor of 137CFM/SQin or the 146CFM/SQin that most of us use. The equation uses the window area at every lift increment, the theoretical maximum and a ratio of effective area and actual flow area. Go to my web site at http://webpages.charter.net/dsda/
I have uploaded an XL spread sheet showing the discharge Coe.
(2) Velocity profile Coe. Based on overall volume of runner, Mean velocity , average flow curve and valve area exposed to chamber.
Its basically a velocity average of the intake runner column verses valve area
There a LOT of other ratios and Coe you should use and know. You should figure out what the mean gas velocities are in the range of VE the engine will be running in. You should figure out what the intake tuned power band (Tuned length of runner) is verses piston speed. You should know the overall runner volume to cylinder ratio. These are just a few but you get the idea. If you know all this about an engine you can make educated decisions on what to do next. otherwise your just fumbling around in the dark. It saves a lot of money, time and aggravation.
The 116 cfm/SQin I was referring to is a simplified coefficient based on area and flow at 28 inches depression. It rates the efficiency of the area exposed to the cylinder ( valve head diameter ) and the flow going into the cylinder as it relates to bore diameter, chamber design and shrouding as well as the port design itself. There are many coefficients that I use and this is by far the simplest. You find the valve head area
Diameter*Diameter*.7854=Area
then you divide the flow by the area. Its that simple. Plot the curve for every head you do. You will start to see what's going on.
You will find that when you stick a really big valve in a head to gain some more CFM that the CFM/SQin ( efficiency) drops off. In other words, that three or five CFM you gained by putting in a big valve just cost you 20 horsepower because you killed the efficiency of the port.
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at http://www.rehermorrison.com
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Darin Morgan
Guest
Posted: Wed Sep 08, 2004 7:43 am Post subject: CFM/SQin
--------------------------------------------------------------------------------
Actually, the CFM/SQin calculation is not a true Coefficient because its not based on a theoretical maximum. Its actually a Ratio. Sorry, I am still not awake this morning.
.
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shawn
New Member
Joined: 11 Aug 2003
Posts: 28
Posted: Wed Sep 08, 2004 9:38 am Post subject:
--------------------------------------------------------------------------------
great info. Darin. I think you should write that book, too. Does your class get into this type of information or is it more of an entry level type class?Also, is there any books out that would explain these coe's in more detail?
shawn
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bill jones
New Member
Joined: 05 Sep 2004
Posts: 37
Location: salt lake city, ut
Posted: Wed Sep 08, 2004 11:25 am Post subject:
--------------------------------------------------------------------------------
-Thanks for the replys.
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Darin Morgan
Guest
Posted: Wed Sep 08, 2004 1:14 pm Post subject: Reher Morrison engine building school
--------------------------------------------------------------------------------
I dont get into all of it but I do go over the basics. Look for an advanced cylinder head school in the next year or two.
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Darin Morgan
Guest
Posted: Wed Sep 08, 2004 1:27 pm Post subject: CFM/SQin
--------------------------------------------------------------------------------
shawn wrote:
I think he is refering to flow vs. valve diameter at the standard 28"'s, with a specific type of valve job. This would put a 2.500 inch at about 569 cfm.Is this right Darin?I think this is also a threshold that the headporters strive for.With a given bore diameter and engine combo, the intake valve diameter is limited. It's up to the smart guys like Darin to squeeze as much flow as possible out of this as possible and still have something that will accelerate down the track. How did I do Darin?
Shawn
A Pro Stock head will move about 576cfm at one inch lift (about 350 ft/sec and 280 ft/sec average). Thats,,,,
2.515*2.515*.7854=4.967 SQ/in
576/4.967=115.9 CFM/SQin
We measure up to 1.100 lift because thats how high we lift the valve.
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bill jones
New Member
Joined: 05 Sep 2004
Posts: 37
Location: salt lake city, ut
Posted: Wed Sep 08, 2004 3:35 pm Post subject:
--------------------------------------------------------------------------------
-how do you calibrate your flowbench?
-do you use a sharp edge orifice?
-What do you consider a standard cubic foot of air to weigh in pounds?
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learner
Member
Joined: 06 Jul 2003
Posts: 78
Posted: Wed Sep 08, 2004 4:50 pm Post subject:
--------------------------------------------------------------------------------
Class.....? could someone fill me in on these classes. Is it a seminar, classroom setting, times, places...I know i couldn't be so lucky for it to be an online class since i live 2500 miles from there.
Thanks
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New Member
Joined: 11 Aug 2003
Posts: 28
Posted: Tue Sep 07, 2004 6:03 pm Post subject:
--------------------------------------------------------------------------------
I think he is refering to flow vs. valve diameter at the standard 28"'s, with a specific type of valve job. This would put a 2.500 inch at about 569 cfm.Is this right Darin?I think this is also a threshold that the headporters strive for.With a given bore diameter and engine combo, the intake valve diameter is limited. It's up to the smart guys like Darin to squeeze as much flow as possible out of this as possible and still have something that will accelerate down the track. How did I do Darin?
Shawn
Back to top
Darin Morgan
Guest
Posted: Wed Sep 08, 2004 7:32 am Post subject: Coe
--------------------------------------------------------------------------------
This subject is far to complex to get into on a message board because a small book can be written on this subject alone. If you do heads for living you need to study and understand flow coefficients and discharge coefficients as well as the proper use of ratios. Without a thorough understanding of these concepts you will not be able to design the most efficient port possible for a given engine combination. Raw flow figures are Satan's tool of deception! I don't mean to get to dramatic but that pretty much sums up my view about people who use flow figures to rate a cylinder heads efficiency. There are many coefficients that I use and CFM/SQin is by far the simplest. The other coefficients you should learn and use are,
(1) Discharge Coe. Based on theoretical maximum such as the SAE factor of 137CFM/SQin or the 146CFM/SQin that most of us use. The equation uses the window area at every lift increment, the theoretical maximum and a ratio of effective area and actual flow area. Go to my web site at http://webpages.charter.net/dsda/
I have uploaded an XL spread sheet showing the discharge Coe.
(2) Velocity profile Coe. Based on overall volume of runner, Mean velocity , average flow curve and valve area exposed to chamber.
Its basically a velocity average of the intake runner column verses valve area
There a LOT of other ratios and Coe you should use and know. You should figure out what the mean gas velocities are in the range of VE the engine will be running in. You should figure out what the intake tuned power band (Tuned length of runner) is verses piston speed. You should know the overall runner volume to cylinder ratio. These are just a few but you get the idea. If you know all this about an engine you can make educated decisions on what to do next. otherwise your just fumbling around in the dark. It saves a lot of money, time and aggravation.
The 116 cfm/SQin I was referring to is a simplified coefficient based on area and flow at 28 inches depression. It rates the efficiency of the area exposed to the cylinder ( valve head diameter ) and the flow going into the cylinder as it relates to bore diameter, chamber design and shrouding as well as the port design itself. There are many coefficients that I use and this is by far the simplest. You find the valve head area
Diameter*Diameter*.7854=Area
then you divide the flow by the area. Its that simple. Plot the curve for every head you do. You will start to see what's going on.
You will find that when you stick a really big valve in a head to gain some more CFM that the CFM/SQin ( efficiency) drops off. In other words, that three or five CFM you gained by putting in a big valve just cost you 20 horsepower because you killed the efficiency of the port.
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at http://www.rehermorrison.com
Back to top
Darin Morgan
Guest
Posted: Wed Sep 08, 2004 7:43 am Post subject: CFM/SQin
--------------------------------------------------------------------------------
Actually, the CFM/SQin calculation is not a true Coefficient because its not based on a theoretical maximum. Its actually a Ratio. Sorry, I am still not awake this morning.
.
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shawn
New Member
Joined: 11 Aug 2003
Posts: 28
Posted: Wed Sep 08, 2004 9:38 am Post subject:
--------------------------------------------------------------------------------
great info. Darin. I think you should write that book, too. Does your class get into this type of information or is it more of an entry level type class?Also, is there any books out that would explain these coe's in more detail?
shawn
Back to top
bill jones
New Member
Joined: 05 Sep 2004
Posts: 37
Location: salt lake city, ut
Posted: Wed Sep 08, 2004 11:25 am Post subject:
--------------------------------------------------------------------------------
-Thanks for the replys.
Back to top
Darin Morgan
Guest
Posted: Wed Sep 08, 2004 1:14 pm Post subject: Reher Morrison engine building school
--------------------------------------------------------------------------------
I dont get into all of it but I do go over the basics. Look for an advanced cylinder head school in the next year or two.
Back to top
Darin Morgan
Guest
Posted: Wed Sep 08, 2004 1:27 pm Post subject: CFM/SQin
--------------------------------------------------------------------------------
shawn wrote:
I think he is refering to flow vs. valve diameter at the standard 28"'s, with a specific type of valve job. This would put a 2.500 inch at about 569 cfm.Is this right Darin?I think this is also a threshold that the headporters strive for.With a given bore diameter and engine combo, the intake valve diameter is limited. It's up to the smart guys like Darin to squeeze as much flow as possible out of this as possible and still have something that will accelerate down the track. How did I do Darin?
Shawn
A Pro Stock head will move about 576cfm at one inch lift (about 350 ft/sec and 280 ft/sec average). Thats,,,,
2.515*2.515*.7854=4.967 SQ/in
576/4.967=115.9 CFM/SQin
We measure up to 1.100 lift because thats how high we lift the valve.
Back to top
bill jones
New Member
Joined: 05 Sep 2004
Posts: 37
Location: salt lake city, ut
Posted: Wed Sep 08, 2004 3:35 pm Post subject:
--------------------------------------------------------------------------------
-how do you calibrate your flowbench?
-do you use a sharp edge orifice?
-What do you consider a standard cubic foot of air to weigh in pounds?
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learner
Member
Joined: 06 Jul 2003
Posts: 78
Posted: Wed Sep 08, 2004 4:50 pm Post subject:
--------------------------------------------------------------------------------
Class.....? could someone fill me in on these classes. Is it a seminar, classroom setting, times, places...I know i couldn't be so lucky for it to be an online class since i live 2500 miles from there.
Thanks
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10-08-2004, 09:57 PM
#409
6600 rpm clutch dump of death Administrator
Thread Starter
Darin Morgan
Guest
Posted: Thu Sep 09, 2004 10:01 am Post subject: Mass of gas and oriface
--------------------------------------------------------------------------------
bill jones wrote:
-how do you calibrate your flowbench?
-do you use a sharp edge orifice?
-What do you consider a standard cubic foot of air to weigh in pounds?
I still use the Oriface plate that came witt the bench form SuperFlow.
One cubic foot of "air" weighs .074 to .078 lbs. or 1.25grams
One cubic inch of air weighs .00000000045 lbs or .00069 grams.
Air consists of rouphly 79% Nitrogen, 20% Oxygen and 1% of other gasses like argon.
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shawn
New Member
Joined: 11 Aug 2003
Posts: 28
Posted: Thu Sep 09, 2004 4:39 pm Post subject:
--------------------------------------------------------------------------------
"Class.....? could someone fill me in on these classes. Is it a seminar, classroom setting, times, places...I know i couldn't be so lucky for it to be an online class since i live 2500 miles from there. "
Darin and the guys at Reher-Morrison have a engine building class that they run at the shop. You can check it out at their web site.
Darin, i would love to see you do an advanced class. Sign me up!I looked on the SAE site and searched for discharge coe.'s and came up with quite a few papers avaliable. Is there some that you know of that cover what you have discussed?Not that i'm cheap or anything, well maybe i am, but at $12.00 a whack i don't want one that covers something non applicable.Or maybe a book avaliable that would go into more detail?
thanks again,
shawn
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Guest
Posted: Fri Sep 10, 2004 6:44 am Post subject:
--------------------------------------------------------------------------------
shawn wrote:
"Class.....? could someone fill me in on these classes. Is it a seminar, classroom setting, times, places...I know i couldn't be so lucky for it to be an online class since i live 2500 miles from there. "
Darin and the guys at Reher-Morrison have a engine building class that they run at the shop. You can check it out at their web site.
Darin, i would love to see you do an advanced class. Sign me up!I looked on the SAE site and searched for discharge coe.'s and came up with quite a few papers avaliable. Is there some that you know of that cover what you have discussed?Not that i'm cheap or anything, well maybe i am, but at $12.00 a whack i don't want one that covers something non applicable.Or maybe a book avaliable that would go into more detail?
thanks again,
shawn
I have been a member of SAE for over a decade now and I can tell you from experience that its well worth it! Whether or not the papers are "non applicable" or not, you will always learn something by reading them. I have stacks and stacks of SAE papers dealing with everything related to Poppet valve technology, induction system design, Inertial tuning, High amplitude wave " shock wave tuning", Fuel injection design, carburetors and everything in between. Go get the CD that cover the last ten years or so. It cost about $375.00 and you will be reading for the next five months! There is a wealth of information out there, its just knowing where to look. The SAE is the first place I looked. Look up the paper on " An Analyses of the Volumetric Efficiency characteristics of 4 stroke cycle engines using the mean inlet Mach number " It paper number 790484. There math is a little screwy but you will get the drift of what they are talking about. It deals with air velocities in the intake tract and how fast is to fast. It deals with high velocity issues in the intake tract and sheds some light on why engines nose over due to exceeding the " mean" .55 Mach number.
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eraser44
New Member
Joined: 10 Sep 2004
Posts: 3
Posted: Fri Sep 10, 2004 10:36 am Post subject: 116 cfm
--------------------------------------------------------------------------------
Darin,
Is this a fixed ratio for all cu in engines, or just 500" in Pro Stock? It would seem smaller motors need less flow. I have a 263" Buick V6, 2.125" intake valve, 322 cfm flow @ .800. With your formula I get a ratio of 91.83, but if I take the ratio of 263" to 500" (53%) then 53% of 576 cfm on your Pro Stock heads = 305 cfm on my little motor which puts me in the ball park.
Right or wrong?
Thanks
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Darin Morgan
Guest
Posted: Fri Sep 10, 2004 12:29 pm Post subject: Re: 116 cfm
--------------------------------------------------------------------------------
eraser44 wrote:
Darin,
Is this a fixed ratio for all cu in engines, or just 500" in Pro Stock? It would seem smaller motors need less flow. I have a 263" Buick V6, 2.125" intake valve, 322 cfm flow @ .800. With your formula I get a ratio of 91.83, but if I take the ratio of 263" to 500" (53%) then 53% of 576 cfm on your Pro Stock heads = 305 cfm on my little motor which puts me in the ball park.
Right or wrong?
Thanks
Its a big mistake to try and use ratios like that. You cant take a crossectional area or flow curve from a 500 and use a ratio to downscale the numbers. It does not work.
Yes the 116cfm/SQin is for canted valve heads with very efficient chamber designs. A wedge head will see about 95-98 CFM/SQin at .800. Only the most advanced wedge heads on the planet can exceed 100 CFM/SQin.
2.125*2.125*.7854=3.546 SQin
322/3.546=90.80 CFM/SQin
3.546*95 = 336 CFM
You need to plot the ENTIRE curve and not just at .800. The you will see and understand how the changes you make effect the efficiency of the curve and not just the flow curve itself.
Will your head be able to hit 336 CFM? Maybe not but that's what your shooting for! Maybe a smaller valve will flow more CFM/SQin due to chamber shrouding? Maybe you move the head over with offset dowels and unshroud the valve? Maybe you work on the seat/throat area to make it turn the air more efficiently. Its a target. Its a theoretical maximum. You still need to plot the entire curve for a couple of months before it becomes intuitive. There are so many other variables to consider as well. Dont get tunnel vision and let just this one blind you. Keep your velocitys in check as well. Thats just as important..
.
.
.
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at http://www.rehermorrison.com
Guest
Posted: Thu Sep 09, 2004 10:01 am Post subject: Mass of gas and oriface
--------------------------------------------------------------------------------
bill jones wrote:
-how do you calibrate your flowbench?
-do you use a sharp edge orifice?
-What do you consider a standard cubic foot of air to weigh in pounds?
I still use the Oriface plate that came witt the bench form SuperFlow.
One cubic foot of "air" weighs .074 to .078 lbs. or 1.25grams
One cubic inch of air weighs .00000000045 lbs or .00069 grams.
Air consists of rouphly 79% Nitrogen, 20% Oxygen and 1% of other gasses like argon.
Back to top
shawn
New Member
Joined: 11 Aug 2003
Posts: 28
Posted: Thu Sep 09, 2004 4:39 pm Post subject:
--------------------------------------------------------------------------------
"Class.....? could someone fill me in on these classes. Is it a seminar, classroom setting, times, places...I know i couldn't be so lucky for it to be an online class since i live 2500 miles from there. "
Darin and the guys at Reher-Morrison have a engine building class that they run at the shop. You can check it out at their web site.
Darin, i would love to see you do an advanced class. Sign me up!I looked on the SAE site and searched for discharge coe.'s and came up with quite a few papers avaliable. Is there some that you know of that cover what you have discussed?Not that i'm cheap or anything, well maybe i am, but at $12.00 a whack i don't want one that covers something non applicable.Or maybe a book avaliable that would go into more detail?
thanks again,
shawn
Back to top
Guest
Posted: Fri Sep 10, 2004 6:44 am Post subject:
--------------------------------------------------------------------------------
shawn wrote:
"Class.....? could someone fill me in on these classes. Is it a seminar, classroom setting, times, places...I know i couldn't be so lucky for it to be an online class since i live 2500 miles from there. "
Darin and the guys at Reher-Morrison have a engine building class that they run at the shop. You can check it out at their web site.
Darin, i would love to see you do an advanced class. Sign me up!I looked on the SAE site and searched for discharge coe.'s and came up with quite a few papers avaliable. Is there some that you know of that cover what you have discussed?Not that i'm cheap or anything, well maybe i am, but at $12.00 a whack i don't want one that covers something non applicable.Or maybe a book avaliable that would go into more detail?
thanks again,
shawn
I have been a member of SAE for over a decade now and I can tell you from experience that its well worth it! Whether or not the papers are "non applicable" or not, you will always learn something by reading them. I have stacks and stacks of SAE papers dealing with everything related to Poppet valve technology, induction system design, Inertial tuning, High amplitude wave " shock wave tuning", Fuel injection design, carburetors and everything in between. Go get the CD that cover the last ten years or so. It cost about $375.00 and you will be reading for the next five months! There is a wealth of information out there, its just knowing where to look. The SAE is the first place I looked. Look up the paper on " An Analyses of the Volumetric Efficiency characteristics of 4 stroke cycle engines using the mean inlet Mach number " It paper number 790484. There math is a little screwy but you will get the drift of what they are talking about. It deals with air velocities in the intake tract and how fast is to fast. It deals with high velocity issues in the intake tract and sheds some light on why engines nose over due to exceeding the " mean" .55 Mach number.
Back to top
eraser44
New Member
Joined: 10 Sep 2004
Posts: 3
Posted: Fri Sep 10, 2004 10:36 am Post subject: 116 cfm
--------------------------------------------------------------------------------
Darin,
Is this a fixed ratio for all cu in engines, or just 500" in Pro Stock? It would seem smaller motors need less flow. I have a 263" Buick V6, 2.125" intake valve, 322 cfm flow @ .800. With your formula I get a ratio of 91.83, but if I take the ratio of 263" to 500" (53%) then 53% of 576 cfm on your Pro Stock heads = 305 cfm on my little motor which puts me in the ball park.
Right or wrong?
Thanks
Back to top
Darin Morgan
Guest
Posted: Fri Sep 10, 2004 12:29 pm Post subject: Re: 116 cfm
--------------------------------------------------------------------------------
eraser44 wrote:
Darin,
Is this a fixed ratio for all cu in engines, or just 500" in Pro Stock? It would seem smaller motors need less flow. I have a 263" Buick V6, 2.125" intake valve, 322 cfm flow @ .800. With your formula I get a ratio of 91.83, but if I take the ratio of 263" to 500" (53%) then 53% of 576 cfm on your Pro Stock heads = 305 cfm on my little motor which puts me in the ball park.
Right or wrong?
Thanks
Its a big mistake to try and use ratios like that. You cant take a crossectional area or flow curve from a 500 and use a ratio to downscale the numbers. It does not work.
Yes the 116cfm/SQin is for canted valve heads with very efficient chamber designs. A wedge head will see about 95-98 CFM/SQin at .800. Only the most advanced wedge heads on the planet can exceed 100 CFM/SQin.
2.125*2.125*.7854=3.546 SQin
322/3.546=90.80 CFM/SQin
3.546*95 = 336 CFM
You need to plot the ENTIRE curve and not just at .800. The you will see and understand how the changes you make effect the efficiency of the curve and not just the flow curve itself.
Will your head be able to hit 336 CFM? Maybe not but that's what your shooting for! Maybe a smaller valve will flow more CFM/SQin due to chamber shrouding? Maybe you move the head over with offset dowels and unshroud the valve? Maybe you work on the seat/throat area to make it turn the air more efficiently. Its a target. Its a theoretical maximum. You still need to plot the entire curve for a couple of months before it becomes intuitive. There are so many other variables to consider as well. Dont get tunnel vision and let just this one blind you. Keep your velocitys in check as well. Thats just as important..
.
.
.
Darin Morgan
R&D-Cylinder Head Dept.
Reher-Morrison Racing Engines
1120 Enterprise Place
Arlington Texas 76001
817-467-7171
FAX-468-3147
Visit our web site at http://www.rehermorrison.com
