cams and wastgate

[crazy torino]

whats a good size waste gate to run on a big 16g evo III gtturbo (4g63 motor) running 30psi of boost.
also me and my friend had a conversation about cams on imports and he said he read that " chainging cams make you loose bottom end"........ however i read about a evo (same 46g3 motor) that stuck hks 272 cams in it and help out extremly. so what say ye ??????

[scottsee]

Im not possitive you would want to run 30 pounds of boost on an Evo III 16g. Max airflow is around 42lb/min and that is acheveable around 22-24psi w/ Cams. Eveything after that will just be reducing the effency of your Turbo & Intercooler and Airflow will drop.

The performance of cams will depend on a few things. They are really designed to supply longer/higer durrations on airflow by change your overlap durration; increasing exhaust speeds, inturn changing the cylinder vacume and turblance of the combustin chamber. Cams are designed to improve Volemetric Effency of your engine, and raise airflow at higher RPM's. The downfall is the lower airflow # at lower RPM's as well as needing to have a slightly higher idle. There're plenty of diffrent girinds available for ones specific goal.

<Edit. it's tough to sumorise Cam's. I've only read a few books on the subject, and am NOT an expert in their abilities..

[scottsee]

Oh yeah, Wategate. 31mm i belive is the stock internal size on that turbo. A common upgrade is the 34mm and even a few people get the 38mm.

[kjewer1]

30 psi on a evo 16g will not be possible, apart from a quick spike at the beggining of the gear. Boost is excess airflow not being "used" by the motor. The 16g doesnt flow enough air to back up 30 psi ahead of the motor If you want to max out the turbo on an internal gate, stay on the stock size! The larger gate will blow open early (force (on the gate) = pressure times area). If you are talking externals, the old standby is the Tial 38, can't go wrong with that valve, and any external is 100 times better than an internal. I could write a novel explaining why citing my past experiences on countless turbos/setups, but I don't have that kind of time

Cams are bigtime. There's a reason that they were one of the first mods on my Evo, after using them on the DSMs. The short version is more airflow at higher rpm, and more airflow at the same boost. If you know my pump gas tuning methodologies, you know why I think this is important. I have never seen a drastic drop in low end performance either. There is some small amount of power loss off boost, but its minimal, and it is certainly still driveable.

[Whathits14]

Most people think 272s are the best for almost any setup, street or strip. Can idle well if you tune properly, and big gains up top and will keep the EVO moving in the upper powerband. Forcedperformance cams are also good, 2's are like 272s and 3's are slightly bigger.

[guitarXgeek]

Originally Posted by Whathits14

Most people think 272s are the best for almost any setup, street or strip. Can idle well if you tune properly, and big gains up top and will keep the EVO moving in the upper powerband. Forcedperformance cams are also good, 2's are like 272s and 3's are slightly bigger.

The FP2's are also slightly cheaper than the HKS 272's. The FP2's also reportedly have a slightly better idle than the HKS's. Just thought I'd add that in