independent LS7 header comparison
Originally Posted by WhiteDiamond
Jason,
Do you have some information to help us understand that dip the LG headers saw at the start of the dyno? The air/fuel ratio isn't labled as to which one is which, either.
Todd
Do you have some information to help us understand that dip the LG headers saw at the start of the dyno? The air/fuel ratio isn't labled as to which one is which, either.
Todd
It's not tuning. The AFR I posted is LG's. Every header is a trade off. The LGs are quite long so theres a dip in torque then as you can see they really come on strong midrange. The Kooks are shorter, the bottom is a little more uniform but they do not make as much peak torque.
even though the exhaust valve situation is less than ideal, this style of head will (have, look at LG's results) make more power than any lsx casting to date.
if the exhaust was such a big deal, a blower/turbo wouldn't work.
if the exhaust was such a big deal, a blower/turbo wouldn't work.
So it would seem the 427 would enjoy a cam with more overlap to help evacuate the cylinder, and an exhaust lobe with more duration (especially at .006"-.050") and more lift than on the intake lobe. At least more so than the LS1,2,6 castings.
Right??
Right??
Originally Posted by Greg Fell
even though the exhaust valve situation is less than ideal, this style of head will (have, look at LG's results) make more power than any lsx casting to date.
if the exhaust was such a big deal, a blower/turbo wouldn't work.
if the exhaust was such a big deal, a blower/turbo wouldn't work.
The LS7 head is (obviously) a seriously kickass piece of hardware, there's no question about that... I just kind of like to play "what if", and was thinking out loud that I think that if it were up to me, I'd trade some intake flow for better exhaust flow. Alas, GM forgot to ask me what I thought (it's not that they didn't care what I thought, see... it's that they forgot to ask...
) when they were designing the LS7 head. 
TECH Regular
Joined: Nov 2005
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From: Arlington, TN
One thought.
The LS7 was based off of the C5R and the C5R's didn't have a full exhaust system to go through per say.
If I'm not mistaken the C5R's went strait headers to side pipes.... with an exhaust line like that you can get away with a small exhaust valve and medium size exhaust lobe...
Why? -> Velocity Velocity Velocity
Unfortunately for a street application you add in a catalytic converter, a couple of bends, a resonator, and a muffler... And total performance for the motor suffers due to lost exhaust velocity...
So you tweak the exhaust port, add in a cam with a larger exhaust lobe with more duration to help get the gas's out of the combustion chamber...
Ya do what ya gotta do.
I remember reading one of the guy's from ET saying the Exhaust side didn't matter... only when your doing a race application can you put 90% of your effort onto the intake and leave the exhaust side weak... in a real world application exhaust needs at least 40% of your attention to make a good total package (then again I could be smoking crack... nope thats meth my fault).
The LS7 was based off of the C5R and the C5R's didn't have a full exhaust system to go through per say.
If I'm not mistaken the C5R's went strait headers to side pipes.... with an exhaust line like that you can get away with a small exhaust valve and medium size exhaust lobe...
Why? -> Velocity Velocity Velocity
Unfortunately for a street application you add in a catalytic converter, a couple of bends, a resonator, and a muffler... And total performance for the motor suffers due to lost exhaust velocity...
So you tweak the exhaust port, add in a cam with a larger exhaust lobe with more duration to help get the gas's out of the combustion chamber...
Ya do what ya gotta do.
I remember reading one of the guy's from ET saying the Exhaust side didn't matter... only when your doing a race application can you put 90% of your effort onto the intake and leave the exhaust side weak... in a real world application exhaust needs at least 40% of your attention to make a good total package (then again I could be smoking crack... nope thats meth my fault).
Here's another comparison. This was done on a different but identical engine on a different day. We were very pleased with the TPIS header performance.
TPIS peak hp: 634 hp
TPIS peak tq: 554 lb-ft
TPIS peak hp: 634 hp
TPIS peak tq: 554 lb-ft
Last edited by Katech_Jason; Apr 12, 2006 at 07:47 PM.
Where were the X pipes on both tests? I know the C6 LG system uses 2 pipes between the X and the headers. I thought I read that the X pipes are best off the collectors. Great stuff!
Originally Posted by Phil99vette
Where were the X pipes on both tests? I know the C6 LG system uses 2 pipes between the X and the headers. I thought I read that the X pipes are best off the collectors. Great stuff!
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