Simple yet Strong. 550/500 418"/243/Fast 102
12-19-2014, 05:45 PM
#61
That is correct. If you read my "Why LSA doesn't matter thread" I discuss this in depth.
With a well tuned primary length and collector design, it is possible to drop the pressure in the cylinder below atmospheric during the overlap event at certain RPM's where the engine comes into tune. This allows the now higher pressure intake charge to accelerate in the intake port and into the cylinder during overlap while the piston is on the exhaust stroke. That is before it's even started to draw on the intake stroke and created any depression in the cylinder.
Without harnessing this phenomenon, a N/A engine will never approach or exceed 100% VE. Since we can jump start cylinder fill and velocity in the intake port before the piston has created any depression, VE% can now increase much higher than it could before. If you read my thread I mentioned, I show some in cylinder pressure diagrams that show how an engine running out of tune(where no negative pressure exists in the cylinder during overlap) cannot even come close to achieving the same cylinder pressure as an engine running in tune.
The same can be said about an engine that uses no overlap, or very little overlap as well.
As far as intake flow at .050-.150, you don't want a lot of intake flow at these lifts...at least IMO. The more the port flows forward at this lift, the better it will flow backwards. There are things you can do with back cuts, seat angles and chamber shape to limit this, but a port that flows really well at low lift doesn't need nearly as much overlap as a head that doesn't. If you used a lot of overlap on a head that flows well at low lift, you can run into issues with reversion during the overlap event. Another unwanted trait of a cylinder head that flows well at low lift is reversion on the IC event. Not something we want if we're to trap as much mixture before the IC event as possible.
Standing up the valve job with steeper angles helps to kill off flow at low lift which is something a lot of head porters employ, especially on the exhaust valve job.
I would not use those lobes. In a high RPM hydraulic roller application I do everything I can to slow down the ramp rate of the lobe so that stability is great even at high RPM. Keeping a hydraulic stable is like skating on ice. You can do it with great control, but if you get out of sync or too aggressive you'll fall and bust your hind end.
I would use a lobe with at least 53-56* cam duration between .006 and .050 lobe lift. Something like a HUC, QXX, QNX, EHX etc. would be my preference. All of those lobes still have exceptional high lift cylinder fill area and will make MUCH more power than the LSK/LSL lobes at high RPM. There is a big difference between a high lift lobe like a LSK and a high lift lobe like a QXX, QNX, high lift HUC etc. etc. etc.
I also think your IVC event is a bit too early for a 13:1 engine and you will incur pumping losses because of it. If the piston is forced to pump against a closed cylinder for too long, and the pressure inside of that cylinder is really high there is a good chance you'll not gain the full benefit from the added compression if the IC event occurs too early. You'll gain something versus a lower compression deal, but if you really want that added compression to make more torque and HP, I'd close the intake later.
Do you have a flow sheet that shows airflow to at least .750-.800" lift?
Also, airflow at 28" is not the same as airflow at 60", 80" or even 100" depression. A running engine will achieve much higher depression than a flow bench can, and on a running engine a port will stall or go turbulent much sooner than it will on a bench. That is why it is a good practice to use a head that flows laminar past your intended cam lift.
If your intake port flows to .700" lift, a .640" lift cam will most likely make more power than a .620" lift cam if the valve train is stable and the lobe design is good for the application. If the intake port flows to .750" lift, then it's a good line of thought that a .660" lift cam, possibly even a .675" lift cam will make more power than a .640" lift cam.
The main thing I'd do is change the lobe design to a much slower seat to seat ramp rate. That doesn't mean you have to lower the valve lift, but the valve train has to be under control or else valve timing will never operate around the parameters it was designed.
If all of this comes together as designed, and the head continues to flow laminar at or above .700" lift I could see a gain of 10-20hp over your current camshaft. If the head is not laminar and goes turbulent at or before .700" lift, I don't see you gaining any power at all. Maybe 3-5hp if that.
With a well tuned primary length and collector design, it is possible to drop the pressure in the cylinder below atmospheric during the overlap event at certain RPM's where the engine comes into tune. This allows the now higher pressure intake charge to accelerate in the intake port and into the cylinder during overlap while the piston is on the exhaust stroke. That is before it's even started to draw on the intake stroke and created any depression in the cylinder.
Without harnessing this phenomenon, a N/A engine will never approach or exceed 100% VE. Since we can jump start cylinder fill and velocity in the intake port before the piston has created any depression, VE% can now increase much higher than it could before. If you read my thread I mentioned, I show some in cylinder pressure diagrams that show how an engine running out of tune(where no negative pressure exists in the cylinder during overlap) cannot even come close to achieving the same cylinder pressure as an engine running in tune.
The same can be said about an engine that uses no overlap, or very little overlap as well.
As far as intake flow at .050-.150, you don't want a lot of intake flow at these lifts...at least IMO. The more the port flows forward at this lift, the better it will flow backwards. There are things you can do with back cuts, seat angles and chamber shape to limit this, but a port that flows really well at low lift doesn't need nearly as much overlap as a head that doesn't. If you used a lot of overlap on a head that flows well at low lift, you can run into issues with reversion during the overlap event. Another unwanted trait of a cylinder head that flows well at low lift is reversion on the IC event. Not something we want if we're to trap as much mixture before the IC event as possible.
Standing up the valve job with steeper angles helps to kill off flow at low lift which is something a lot of head porters employ, especially on the exhaust valve job.
I would not use those lobes. In a high RPM hydraulic roller application I do everything I can to slow down the ramp rate of the lobe so that stability is great even at high RPM. Keeping a hydraulic stable is like skating on ice. You can do it with great control, but if you get out of sync or too aggressive you'll fall and bust your hind end.
I would use a lobe with at least 53-56* cam duration between .006 and .050 lobe lift. Something like a HUC, QXX, QNX, EHX etc. would be my preference. All of those lobes still have exceptional high lift cylinder fill area and will make MUCH more power than the LSK/LSL lobes at high RPM. There is a big difference between a high lift lobe like a LSK and a high lift lobe like a QXX, QNX, high lift HUC etc. etc. etc.
I also think your IVC event is a bit too early for a 13:1 engine and you will incur pumping losses because of it. If the piston is forced to pump against a closed cylinder for too long, and the pressure inside of that cylinder is really high there is a good chance you'll not gain the full benefit from the added compression if the IC event occurs too early. You'll gain something versus a lower compression deal, but if you really want that added compression to make more torque and HP, I'd close the intake later.
Do you have a flow sheet that shows airflow to at least .750-.800" lift?
Also, airflow at 28" is not the same as airflow at 60", 80" or even 100" depression. A running engine will achieve much higher depression than a flow bench can, and on a running engine a port will stall or go turbulent much sooner than it will on a bench. That is why it is a good practice to use a head that flows laminar past your intended cam lift.
If your intake port flows to .700" lift, a .640" lift cam will most likely make more power than a .620" lift cam if the valve train is stable and the lobe design is good for the application. If the intake port flows to .750" lift, then it's a good line of thought that a .660" lift cam, possibly even a .675" lift cam will make more power than a .640" lift cam.
The main thing I'd do is change the lobe design to a much slower seat to seat ramp rate. That doesn't mean you have to lower the valve lift, but the valve train has to be under control or else valve timing will never operate around the parameters it was designed.
If all of this comes together as designed, and the head continues to flow laminar at or above .700" lift I could see a gain of 10-20hp over your current camshaft. If the head is not laminar and goes turbulent at or before .700" lift, I don't see you gaining any power at all. Maybe 3-5hp if that.
12-19-2014, 06:07 PM
#64
I will go back and read that one for sure. I will add it to my Martin's Words of Wisdom document. Is it in Advanced Engine Tech? Thanks for the response. This has turned into a very informative thread. As soon as you think you are catching on you feel dumb again. If you ever get in a gun fight give ma a call, I have a PhD. in those.
When the value of the dollar drops to zero, and society as we know it comes to an end, please come pick me up...that's all I ask.
LOL!!!
It's in Gen 3 engine section and is a sticky.
12-19-2014, 06:14 PM
#65
I got you brother. You will be my first stop. Some one has to rebuild civilization and the LSX community when the world takes a dump.
Last edited by Pray; 12-19-2014 at 06:27 PM.
12-19-2014, 06:27 PM
#67
01-08-2015, 06:17 PM
#69
Great, that whole post is gone. Now it looks like you want to be shot from my post.
On another note, I got one intake port done and I think I found the limit of my abilities with a stinking 2" valve. The good news is that they keep flowing up to .750" lift. To bad it only gained 12cfm by then from .500" lift. Should have just stayed with my first cut and then laid back the SSR. After 9 hours and beating my head against the wall I only gained in the middle and still didn't beat my last heads numbers up top. I will have to check the runner volume to compare. I would bet $100 it is 225-227cc's.
.100..........70
.200........143
.300........217
.400........269
.500........292
.600........293
.700........297
.750........304
What do you think this will do with the combo we talked about the other day? I decided to go with the cam you recommended over the one I came up with. I am going to mill the heads to 60cc's to get my DCR to 8.76. I am a little concerned with my bottom end the more I looked at the OP's graph. I have to deal with 4,100lbs.
On another note, I got one intake port done and I think I found the limit of my abilities with a stinking 2" valve. The good news is that they keep flowing up to .750" lift. To bad it only gained 12cfm by then from .500" lift. Should have just stayed with my first cut and then laid back the SSR. After 9 hours and beating my head against the wall I only gained in the middle and still didn't beat my last heads numbers up top. I will have to check the runner volume to compare. I would bet $100 it is 225-227cc's.
.100..........70
.200........143
.300........217
.400........269
.500........292
.600........293
.700........297
.750........304
What do you think this will do with the combo we talked about the other day? I decided to go with the cam you recommended over the one I came up with. I am going to mill the heads to 60cc's to get my DCR to 8.76. I am a little concerned with my bottom end the more I looked at the OP's graph. I have to deal with 4,100lbs.
01-09-2015, 08:43 AM
#71
Any thoughts?
01-09-2015, 08:56 AM
#72
The other benefit to this set up is that according to my velocity probe, I have the exact same velocity around the entire valve upon exit so my runner us set up to take full advantage of the valves diameter. I will have to check my CD. It just bums me out the the other set of heads I did made it to 297 @ .500 and 310 @ .600. I guess that is what a 2.02" valve will gain you.
01-09-2015, 11:33 AM
#73
I didn't loose anything at all in the middle. It was a freebee cut that only got me gain's. Well, just an extension of Lift I guess. I didn't gain anything. I barely took any off the actual apex since it is so long and undefined. Maybe a couple thou. I just have a little less friction on my inside calipers now. I did however lean it back away from the valve on the straight wall or high side pretty much making a concentric circle matching the valve. The curve of both sides of the SSR now match the roof and the curve of the far wall of the bowl going down into the valve. I really didn't take anything out on the bowl wall furthest from the SSR. Just smoothed it out and opened it up a hair right behind the valve guide. The cross section of the SSR is 2.856" and the cross section of the seat at its narrowest just below the 80* cut is 2.533". I opened the throat to 1.796" which is just under 90%. I think that is what I am limited to at this point. The throat diameter and when I un-shrouded the valve it hut top end and I had to fight to get it back. My mid lift went up though. I think it is the valve job and the throat diameter that are my limiting factors right now. I asked for 38*, 45*, 65*, 75* with the valves sunk a hair to get some seat width on the 38* cut but ended up with a touch of 36*. 45*, 60*, and 80*. My numbers are right in line with AI and TEA up to .500" if not a little better but that .600" number I am down to both. The only thing I can think of now is going after the far curved wall and hitting the roof first and gaining some more height there since the whole port is exactly even right now just canted to match the valve angle. I can also go after the back of the bowl just up from the valve seat and create a little more "roof" area and possibly a little venturi effect. I also didn't widen the bowl much, just enough to get it nice and round.
Any thoughts?
Any thoughts?
Glad you took my advice on the short side and it looks to have done well.
Is your valve opening fixture deflecting as the valve is opening? Kinda weird to see the head pop from .300-.400 instead of from .400-.500?
01-09-2015, 11:35 AM
#74
Thanks. I will give b you a call in about 20 min.
01-09-2015, 06:42 PM
#75
Tried calling the shop twice today and couldn't get a hold of you. There is no deflection. I use a really light spring on the head. The last set I did had the same flow characteristics and the two heads were within 5 cfm of each other up to .500. I made some more cuts and used a string to follow the flow and even though nothing big showed up on the bench I do get a climb up to .600 now. The good news is that my bias is now towards the cylinder wall side so my swirl picked up a bunch. There is no turbulence up to .690 lift now. .600 could be 300 cfm but I will have to get it back on the SF600. My bench only shows me gains or losses.
01-10-2015, 12:46 PM
#77
Tried calling the shop twice today and couldn't get a hold of you. There is no deflection. I use a really light spring on the head. The last set I did had the same flow characteristics and the two heads were within 5 cfm of each other up to .500. I made some more cuts and used a string to follow the flow and even though nothing big showed up on the bench I do get a climb up to .600 now. The good news is that my bias is now towards the cylinder wall side so my swirl picked up a bunch. There is no turbulence up to .690 lift now. .600 could be 300 cfm but I will have to get it back on the SF600. My bench only shows me gains or losses.
Shoot me an email martin@tick-performance.com and I'll shoot it over to you.