Vizard's LSA - CI/Inch Valve Diameter chart
09-19-2007, 11:49 AM
#61
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Originally Posted by LS1curious
hmm I think you don't understand highoutput 4cylinder ITB stuff. 90 kpa idle on its best day.
No matter what you do to a carburator it'll never be anything beyond a gas can with a straw sticking out of it period.
You can add a ton of air bleeding and emulsifiying orifices and circuts you can redesign the discharge orifices all day but its doesn't change that fact ever. A carberator is a pressure differential device. No pressure difference no function. Sure a carb can tolerate low idle vacum becuase the venturi it self genrates Some of the signal. but as soon as that fuel hits the plenum it falls right out of suspension.
we have a huge difference between a Electronics guy and someone who does what he talks about for a living. Honestly the EFI system is not holding the EFI pro-mod back. Something else in the system is.Could be the ratting for flow on the TB's honestly. You have one TB with a rating at 1.5 inchs of mercury and another at 28inch of water deprssion. You also have a laminar flow elemnt in the carberator which is the venturi itself the helps drive airflow through the plate.
but I am done with this topic. EFI wins if carbs are so great why is proof is in the pudding. F1 runs EFI. if a carb had an advatage I think the companies spending millions daily to find HP would be all over it.
If you want to talk fankly about fuel atomoization differences between carberators and EFI glad to have that discussion.
No matter what you do to a carburator it'll never be anything beyond a gas can with a straw sticking out of it period.
You can add a ton of air bleeding and emulsifiying orifices and circuts you can redesign the discharge orifices all day but its doesn't change that fact ever. A carberator is a pressure differential device. No pressure difference no function. Sure a carb can tolerate low idle vacum becuase the venturi it self genrates Some of the signal. but as soon as that fuel hits the plenum it falls right out of suspension.
we have a huge difference between a Electronics guy and someone who does what he talks about for a living. Honestly the EFI system is not holding the EFI pro-mod back. Something else in the system is.Could be the ratting for flow on the TB's honestly. You have one TB with a rating at 1.5 inchs of mercury and another at 28inch of water deprssion. You also have a laminar flow elemnt in the carberator which is the venturi itself the helps drive airflow through the plate.
but I am done with this topic. EFI wins if carbs are so great why is proof is in the pudding. F1 runs EFI. if a carb had an advatage I think the companies spending millions daily to find HP would be all over it.
If you want to talk fankly about fuel atomoization differences between carberators and EFI glad to have that discussion.
09-19-2007, 12:03 PM
#62
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That may be true....
But peak power is only a number.
Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.
A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
But peak power is only a number.
Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.
A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
09-19-2007, 12:06 PM
#63
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the F1 guys seem to have found a way to fix that problem by locating the injector at the top of or just above the velocity stack in the TB. In doing so they get a much better atomoization and then its all straight toss up. It takes a bit of refinament and testing to find the optimal angle and hieght but locating the injector above the Blades on a single plane would be very close. In fact I am wating to see somebody ambitous enough to try a big injector TBI 4bbl setup vs a carb. Very straightforward A-B tsting.
Originally Posted by WOTFMAN
Carbs make more power then EFI because of fuel atomization properties. The droplets turn into vapor in a well ported intake and cylinder head. So fine a mist/vapor that you can make the power over EFI.
09-19-2007, 12:32 PM
#64
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There are plenty of dual injector ITB setups that run a primary injector close to the valve, and a secondary injector at the mouth of the velocity stack or trumpet.
09-19-2007, 12:38 PM
#66
Originally Posted by stevieturbo
That may be true....
But peak power is only a number.
Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.
A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
But peak power is only a number.
Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.
A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
09-19-2007, 02:08 PM
#67
This has gotten pretty far off track and turned in to a Carb vs EFI post, not the intended Vizad LSA argument.
I have a few questions based more on the original topic.
Say you have 2 cams specs first one being a popular cam:
Cam 1 (108 icl / 110l lsa)
Intake
.006 - .050 - .200
294 -- 243 -- 164
Exhaust
.006 - .050 - .200
300 -- 250 -- 169
IVO .006 - .050 - .200
------ 39* - 13.5* - (-26) --- BTDC
IVC .006 - .050 - .200
------ 75 --- 49.5 ---10 ----- ABDC
EVO .006 - .050 - .200
------ 82 ----57 ----- 12 ----- BBDC
EVC .006 - .050 - .200
------ 38 ----13 -- (-32) ----- ATDC
26.5* overlap
11.03 SCR - 8.02 DCR
Cam 2 (106icl 108lsa)
Intake
.006 - .050 - .200
286 -- 236 -- 159
Exhaust
.006 - .050 - .200
286 -- 236 -- 159
IVO .006 - .050 - .200
------ 37 -- 12* - (-26.5) --- BTDC
IVC .006 - .050 - .200
------ 69 --- 44 ---5.5 ----- ABDC
EVO .006 - .050 - .200
------ 73 ----48 ----- 9.5 -- BBDC
EVC .006 - .050 - .200
----- 33 ----- 8 --- (-30.5) - ATDC
20* overlap
11.03 SCR - 8.47 DCR
Wouldn't cam #2
Have less chance of reversion?
Make more bottom end TQ?
Carry TQ/RPM just about as far as cam 1?
Be "easier" to tune?
I have a few questions based more on the original topic.
Say you have 2 cams specs first one being a popular cam:
Cam 1 (108 icl / 110l lsa)
Intake
.006 - .050 - .200
294 -- 243 -- 164
Exhaust
.006 - .050 - .200
300 -- 250 -- 169
IVO .006 - .050 - .200
------ 39* - 13.5* - (-26) --- BTDC
IVC .006 - .050 - .200
------ 75 --- 49.5 ---10 ----- ABDC
EVO .006 - .050 - .200
------ 82 ----57 ----- 12 ----- BBDC
EVC .006 - .050 - .200
------ 38 ----13 -- (-32) ----- ATDC
26.5* overlap
11.03 SCR - 8.02 DCR
Cam 2 (106icl 108lsa)
Intake
.006 - .050 - .200
286 -- 236 -- 159
Exhaust
.006 - .050 - .200
286 -- 236 -- 159
IVO .006 - .050 - .200
------ 37 -- 12* - (-26.5) --- BTDC
IVC .006 - .050 - .200
------ 69 --- 44 ---5.5 ----- ABDC
EVO .006 - .050 - .200
------ 73 ----48 ----- 9.5 -- BBDC
EVC .006 - .050 - .200
----- 33 ----- 8 --- (-30.5) - ATDC
20* overlap
11.03 SCR - 8.47 DCR
Wouldn't cam #2
Have less chance of reversion?
Make more bottom end TQ?
Carry TQ/RPM just about as far as cam 1?
Be "easier" to tune?
09-20-2007, 06:37 PM
#68
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Originally Posted by stevieturbo
That may be true....
But peak power is only a number.
Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.
A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
But peak power is only a number.
Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.
A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
Bottom line is a person with a high knowledge base on carbs can and will outperform the EFI guy. Argue all you want, show me proof that EFI will outperform it in a series as tight as NASCAR or Pro Stock.
09-20-2007, 06:39 PM
#69
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Originally Posted by LIL SS
This has gotten pretty far off track and turned in to a Carb vs EFI post, not the intended Vizad LSA argument.
I have a few questions based more on the original topic.
Say you have 2 cams specs first one being a popular cam:
Cam 1 (108 icl / 110l lsa)
Intake
.006 - .050 - .200
294 -- 243 -- 164
Exhaust
.006 - .050 - .200
300 -- 250 -- 169
IVO .006 - .050 - .200
------ 39* - 13.5* - (-26) --- BTDC
IVC .006 - .050 - .200
------ 75 --- 49.5 ---10 ----- ABDC
EVO .006 - .050 - .200
------ 82 ----57 ----- 12 ----- BBDC
EVC .006 - .050 - .200
------ 38 ----13 -- (-32) ----- ATDC
26.5* overlap
11.03 SCR - 8.02 DCR
Cam 2 (106icl 108lsa)
Intake
.006 - .050 - .200
286 -- 236 -- 159
Exhaust
.006 - .050 - .200
286 -- 236 -- 159
IVO .006 - .050 - .200
------ 37 -- 12* - (-26.5) --- BTDC
IVC .006 - .050 - .200
------ 69 --- 44 ---5.5 ----- ABDC
EVO .006 - .050 - .200
------ 73 ----48 ----- 9.5 -- BBDC
EVC .006 - .050 - .200
----- 33 ----- 8 --- (-30.5) - ATDC
20* overlap
11.03 SCR - 8.47 DCR
Wouldn't cam #2
Have less chance of reversion?
Make more bottom end TQ?
Carry TQ/RPM just about as far as cam 1?
Be "easier" to tune?
I have a few questions based more on the original topic.
Say you have 2 cams specs first one being a popular cam:
Cam 1 (108 icl / 110l lsa)
Intake
.006 - .050 - .200
294 -- 243 -- 164
Exhaust
.006 - .050 - .200
300 -- 250 -- 169
IVO .006 - .050 - .200
------ 39* - 13.5* - (-26) --- BTDC
IVC .006 - .050 - .200
------ 75 --- 49.5 ---10 ----- ABDC
EVO .006 - .050 - .200
------ 82 ----57 ----- 12 ----- BBDC
EVC .006 - .050 - .200
------ 38 ----13 -- (-32) ----- ATDC
26.5* overlap
11.03 SCR - 8.02 DCR
Cam 2 (106icl 108lsa)
Intake
.006 - .050 - .200
286 -- 236 -- 159
Exhaust
.006 - .050 - .200
286 -- 236 -- 159
IVO .006 - .050 - .200
------ 37 -- 12* - (-26.5) --- BTDC
IVC .006 - .050 - .200
------ 69 --- 44 ---5.5 ----- ABDC
EVO .006 - .050 - .200
------ 73 ----48 ----- 9.5 -- BBDC
EVC .006 - .050 - .200
----- 33 ----- 8 --- (-30.5) - ATDC
20* overlap
11.03 SCR - 8.47 DCR
Wouldn't cam #2
Have less chance of reversion?
Make more bottom end TQ?
Carry TQ/RPM just about as far as cam 1?
Be "easier" to tune?
09-20-2007, 10:29 PM
#71
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Prize Indeed
Originally Posted by edcmat-l1
Well, duh. Never said it was. Overlap is nothing more than how long both valves are off their repective seats.
Yeah. And the ability to breathe can be influenced, both positively, and negatively by valve events/overlap.
Not really sure what you mean there. Overlap is ONLY defined as degrees of rotation over which both valves are open. So, thats another DUH statement.
Virtually all of the components and specs you've regarded as meaningless, all have an effect on what cam specs will work best.
Yeah. And the ability to breathe can be influenced, both positively, and negatively by valve events/overlap.
Not really sure what you mean there. Overlap is ONLY defined as degrees of rotation over which both valves are open. So, thats another DUH statement.
Virtually all of the components and specs you've regarded as meaningless, all have an effect on what cam specs will work best.
09-22-2007, 02:55 PM
#72
I'm trying to understand why. I'm happy to admit I don't know everything, but know one explains why so I try to use logic, and logic tells me that there is less over lap. I have always been under the impression overlap can aid in reversion. Is it due to where the exhaust valve opens?
Originally Posted by WOTFMAN
Cam # 1 will make the better low end grunt. Cam 2 would have more chance of reversion if the intake and cylinder head ports werent tuned for what that cam will want as far as runner length goes.
10-13-2007, 09:46 AM
#73
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Anway, I found David Vizard's article called Perfect Timing he wrote specifically for GMHTP in Oct-03. It's a 6 page article geared toward Gen III engines. I also found another article he wrote called Setting the Record straight: Exploding Valvetrain Myths. Both are good articles about camshafts with good images to reinforce his points.
10-13-2007, 12:27 PM
#74
TECH Senior Member
First of all these cams aren't even in the same league. Can't even compare them.
You are comparing a T-Rex size cam to like a TSP torquer.
Look at the IVC and EVO of both cams it is pretty obvious that cam2 will come on sooner in the rpms, peak sooner, peak trq sooner.
So basically minor bolt on, stock gears the cam2 would whoop the others *** in quarter and it wouldn't even be funny.
But if you optimize the combo of both, then you are comparing a midget Asian elephant to a mamoth.
