ViNNiE_NB

Highly tuned engines, equipped with free-flowing exhaust, suffer from low-end performance caused by too little exhaust back-pressure. This situation allows some of the incoming fuel/air charge to leave the cylinder with the exhaust. The muffler supplies just the right amount of back-pressure to assure that the incoming air/fuel charge stays in the cylinder, assuring maximum horsepower and torque.
As engine speeds and load conditions change, so do pressure waves in the exhaust system.
So, to say. 0 backpressure is not good and probably not obtainable...A little back pressure is good...3psi or less... You could measure the back pressure in your exhaust with a 0-15psi gauge, just make sure everything is high temp resistant....
OEMs use back pressure to get the best milage from their cars, typically their back pressure is quite high which gives the car more low end torque/hp....
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ViNNiE_NB

Oh and this is helpful knowledge...

http://www.ztechz.net/id7.html

Buck

I am going to say it again, rephrasing.

in a turbo application, the TURBO will provide plenty of "backpressure". Screw the exhaust, I mean realistically you would want an open dump in a turbo application. Again, get your exhaust as free-flowing as possible with a turbo.

ViNNiE_NB

Yes but my whole argument was why so big with such a small turbo and little HP. Yes u don't relatively need back pressure with a turbo application, but u do need some, it all has to do with the placement of the engine and the size of the turbo. Back pressure can be helpful, I say go with a 3" exhaust and little back pressure if ur gonna push 350+WHP. Other then that u can still run ur stock 2.25" and get 300WHP easily and save money on not buying a huge exhaust.

Buck

Agreed, if you aren't going for really big goals it makes sense to avoid unnecessary purchases.

lilaznjdawg

I have a greddy turbo kit for sale if you want it. IT comes with everything including fuel injectors, a new fuel rail, pre-tapped oil pan, dezod wiring harness for a ultimate e-manage. let me know.!