Ok so I bought a gmpp header, catless zzp downpipe, and a gmpp catback from a member on here. I am curious as to how much power will I receive from this combination? I have stage 2, and injen intake for now. After these things I will be getting 2.8, meth, fmic, and a tune.

 

with the things you just purchased, maybe 10-12hp

 

thats it? I was expecting maybe 15-20whp.

 

Yea 5-10 is a little low.

15-20 is a pretty good guess.

realisitic at least.

 

Cool. thats awesome. Now that I have the new header and dp on, will I be reading lower boost?(these things are not installed yet)

 

It will probably be a little lower since you are reducing the back pressure.

But you should replace that GMPP manifold. The only reason to run a GMPP exhaust manifold is if you are under warranty. If you are not...I wouldn't even bother installing it. Get a header!

 

The only reason Im gonna run the gmpp header is im getting it pretty cheap. Plus I like having gmpp parts.

 

15-20whp with the gm manifold downpipe and gm exhaust? i highly doubt it. maybe around 12 or so to the wheels.

reducing the backpressure i sGOOD not BAD. i don't know why so many people think it's a bad thing to get rid of backpressure...

boost will be lower.

 

10-15, 15 on the high side. That WHP. Obviously your crank hp will be in the 15-20 range "as advertised." lol.

It would probably be good for like 1 mph in the 1/4.

 

I never said it was bad. Why do you think I said he should replace the GMPP Exhaust manifold? Because he should reduce the back pressure even more.

 

i think people just add up the advertised horsepower. they don't realize it doesn't work that way.

 

I was guessing 15-20whp. I can see why I wouldnt get 15whp from all this. I have heard that the gmpp is a very free flowing exhaust. The downpipe is catless and the header is honed a lil bigger.

 

my bad, i misread. i didn't realize you were talking about the boost, i thought you were talking about the hp. you were spot on.

the gmpp will not be as free flowing as a 2.5" exhaust. with a 2.8" pully and other mods especially, i would consider getting a 2.5" exhaust, and a different manifold. the gmpp mani is almost worthless compared to other parts that are out there.

 

Esp with a catless dp. The catless dp out flows the GMPP Manifold.

https://www.cobaltss.net/forums/2-0l-lsj-performance-tech-47/flow-calculation-some-lsj-parts-67539/

 

you can get a clear image equal length for barely over 200, that's a bargain if you ask me. I only paid 40 bucks for my pacesetter, but it's only got 1.5" primaries, so I'll upgrade in the future.

 

Oh man, that Downpipe to GMPP catback is going to bottleneck like a motha *****......My car picked up 1mph from taking the GMPP off and going with a 2.5"..This was with a 3" DP to the GMPP and it was awful, i felt a nice increase right after my 2.5" got put on.