Hello guys. I'm looking for help from the turbo gurus here. I will be turbo'ing my '01 5.3L ECSB soon, details in sig. The engine will be mostly stock with a turbo cam. The plan is to go with a KB kit and start with an MP70 turbo. But I would like to build in the ability to go bigger in the future, like 76mm or larger. The goal is 450-500rwhp with the MP70, and up to 600rwhp later on.

Will a 3.5" DP suffice, or would it be wise to go with a 4" in the beginning? I know a 4" DP is overkill for an MP70, but what about for a 76mm or bigger? Any downsides to a 4" DP besides the added cost? Fitment? Reduced power with the smaller turbo?

Thanks!

 

No expert but I think a 3.5 will support even your higher goals. Also full 4" exhaust will be louder

 

I'm using a 3.5" with mine, 790/939 rwhp/tq and 10.90@126 with a 365" and small tc76. You will be plenty fine with a 3.5" especially with the 5.3. A higher end turbo like a precision, turbonetics or even magnum ball bearing will gain you more than the bigger down pipe.

 

Why don't you just start out with a t 76 to begin with and save you trouble later on.
Oh yea.3.5 inch dp here and goes into a 4" pipe

 

Yea, start with a 76mm and save some time down the road..

 

I already have the 70mm sitting on my desk, and would like to give it a shot before going larger. Who knows, the 70mm might be enough to keep me happy

Sounds like 3.5" is the way to go. Thanks guys!

 

70mm on 10# will be fun!

 

This is my plan for now!

You should be able to hit your "later" goal of 600hp with the 70mm 3.5" dp/exhaust, but will probably take around 16-18psi which is pretty damn close to maxing that 70 out with the 5.3L. The 70 will also spool just a little quicker as well. I ordered my 70mm kit with the intention of going turbo cam and 12+ psi down the road and I only have a 3" dp. I will be running 3.5"-4" after the 3" dp and cutout I have.

Hope that helps!

 

Um Guys, Foose04 is making over 700rwhp with a T76 and only a 3" down pipe. The outlet on the turbo is only 3"

 

Who's to say he wouldn't make more power from a bigger down pipe swap..? Send him one for testing ha ha ha