Originally Posted by Ted B

No, I am talking about advancing the intake cam to 110 deg and tightening the LSA to 110 deg to make the engine more mechanically efficient at lower rpm.


No, you do not have a strange 3071. Your 3071 is normal.

You are running 29 psi on pump fuel, and this is what I suspected. This does not appear to be normal, and is almost certainly the cause of your problem.

I don't have any first-hand experience with a 3071 on an EVO, but 29psi is too much boost on pump fuel. In order to run this much boost without getting detonation, the ignition timing has to be retarded quite a bit. If the ignition timing is retarded far enough, the air/fuel charge is still burning when the exhaust valve opens. This creates high EGTs. Also, the mixture is burning inside the turbine housing, which is causing the turbo to spool quicker, and this is the cause of the surging issues. The high heat is not good for the turbo, and you aren't making any more power than you would with less boost and a more realistic ignition curve.

Also, your AFR is a very, very rich 10.5:1. This is only going to make things worse, because you're going to have unburned fuel igniting as soon as it contacts free oxygen in the exhaust system.

What I would do is bring the boost down to ~23-24psi, bring the AFR to ~11.2-11.5:1, and retune the ignition curve. You should make the same power, but you won't have the surging issues and your turbo will last longer.

Originally Posted by Trojan man (Post 3121561)

Wang, that's correct. A larger intake duration bias will typically help out top end breathing. And, obviously most importantly is that the combinations need to be matched appropriately for your goals.

Evojon - No offense, but for your own sake, please do a lot more research into this subject. Cam designs vary SIGNIFICANTLY from OHV and DOHC motors. The cam specs themselves can't even be compared due to the different valvtrain geometries. For example, a 224/224 (single) cam on an ls-1 is a good midrange cam. I don't think anyone would ever run a 224/224 setup on an evo, because the two cam specs represent completely different valve actuation in real life. Also a turbo cam usually has the exact opposite duration setup as an NA or supercharged cam.