Author Topic: Turbo exhaust size (Read 3589 times)

92E36 · « **on:** September 12, 2009, 12:17:22 AM »

im currently in the build of a m42 turbo. i have a 92 e36 318IS 5 speed. i will be running t3 turbo with internal wastegate.OBX exhaust manifold. i will be running standard 8 psi boost. I have a custom built chip for the ECU. It has a front mount intercooler and 328I injectors. What size exhaust tubing should i use for this project.any help would be greatly appreciated. thanks

(please note that in New Zealand we have an exhaust noise limit of 95db.)

Danny707 · « **Reply #1 on:** September 12, 2009, 03:44:54 AM »

2.5" should be fine.

I actually ran 2" on mine and it flowed fine.

Awgy · « **Reply #2 on:** September 12, 2009, 05:23:23 AM »

I will be running 2.5" on 6-8 lbs of boost in a couple of weeks. Ill let you know what i think about it. It will be under 95dbs for sure. Any exhaust modified to be louder is illegal in California.

Got any pics of the build?

AcSchnitzer318is · « **Reply #3 on:** September 13, 2009, 09:38:45 AM »

I'm running 3" from the turbo to the muffler. No cat, muffler is 2.5" magnaflow universal jobbie. Exhaust shop did an awesome job. mandrel bends all the way back.

Flow is great @10psi and it sounds deeper, I guess due to the resonance of the added space. I might add a resonator in the future though.

92E36 · « **Reply #4 on:** September 14, 2009, 02:42:17 AM »

ive got 2 1/4 all the way through from the turbo to a 3" muffler. The turbo exhaust snail outlet is 2".

What do you think???

AcSchnitzer318is · « **Reply #5 on:** September 14, 2009, 09:54:02 AM »

Should be fine at lower boost levels.

I was wrong on my setup. Just took it out last night to get hot coated. Downpipe is actually 2.5" from turbo and is increased to 3" about two feet down.