I dont understand how this occured, but after I got my GMPP Catback and XTC Header installed tonight, I took it out for a test run with my friend. We saw a consistent 17-17.5 lbs of boost and then once we hit 5K in the RPM's it spiked up to 18.5-19 lbs. of boost. How did that happen? Also, I couldn't get my header installed tonight, will that drop the boost then? Currently I have the stock header to the 2.5" DP to the 2.25" Catback. Let me know what you guys think. It is unbelievable tho. Great top end performance gains.

 

Cooler weather.

 

Too much back pressure form the 2.25 inch exhaust

 

thats what my vote would be

 

So is that not a good thing then? Will the addition of the headers lower my boost. And Shortbus, it is pretty cool out here tonight, about 50 degrees. But I thought you were supposed to drop in boost when you open up the exhaust with headers, dp, and catback.

 

Yeah you should drop in pressure when you open up the exhaust side.

 

Yeah, but the stock exhaust is 2.5 and yours is 2.25 which is more restrictive. So it doesn't matter if your header and down pipe flow good, if your exhaust system doesn't then they're no good.

 

He's got the GMPP exhaust... it's a lot more free flowing than stock... it won't create more back pressure.

 

Okay, I understand that and the reasoning. Is it a cause for concern that the numbers I am seeing are occuring? Is my car okay or is it something to worry about?

 

I have also heard that from a lot of members too.

 

smaller dostn mean it flows worse, it flows better than stock and its proven.

 

2.25 vs. 2.5 is not the way to look at it. The way the GMPP 2.25 Exhaust is made, it flows better and is less restictive than Stock. It's like the GMPP header... They are the EXACT SAME header pipe... the GMPP has just been Extrude Honed... it is more free flowing that way.

 

With that being said, what do you think could possibly have given me the boost numbers that I am now seeing?

 

I honestly have no idea... I'm scratching my head. I can ask my buddy at work tomorrow if this hasn't been answered by then... He's got a degree in automotive and knows TONS. The only thing I can think about is that Header... I don't know too much about it... how it compares, Etc... but I wouldn't think that it could possibly be any more restrictive than our crap of a stock header.

Light in head....... Unless you're boost gauge is Screwed up. Like I said... I'll talk with him tomorrow.

 

Is the gmpp exhaust FULL 2.25"?

 

The stock exhaust is still 2.5", the cork is the stock muffler. Remove that and the cork is gone.

 

if the stock downpipe is 2.5, or even 2.25, adding that downpipe will do nothing , because the rest of the exhaust pipe is 2.25...so basically...if any part of your exhaust is 2.25..then the rest of it might as well be because it bottles it up at that point. right? i dont know.

 

Is it possible that when you were putting everything on you might have messed up the cat? A clogged cat will give you higher than normal boost numbers.

 

The muffler is the big problem in your car. The early RL's exhausts were better flowing but didnt sound as good as the SS's. The 06 SS's exhaust sounds 350-ish factory. Sounding better ='s more restriction.

Im guessing the 19psi pump was either your new cat getting situated and clogged up a sec, a misfire, exhaust restriction for a second, almost anything. All I know is that if you see it again, I would get it fixed. Anyway I hope you have a 2.8" pulley cuz if you dont something is wrong.

 

The stock DP is a few sizes , haha . 3" inlet , which necks down to 2" immediately jus before the flexpipe section ....the section between the flexpipe portion an the cat is 2.75" , then after the cat is 2.75 before going back down to 2.5 at the exhaust flange .

 

that 2.25 exhaust is straight through, there would be less pressure on it than there would be on the stock exhaust.

like alpha said it was more than likely the cat.

 

First off, I do have a 2.8" pulley which I was seeing 17.5 lbs before the install of the dp and catback. But I can't see how the cat is/was clogged since it went from the box to the car. I have never seen or heard anything like this before so I am open to all ideas of what it could be. Just a thought, could it be that with the stock header (I think is smaller than dp) is creating a vaccuum with the larger dp leading it to increase boost?

 

What???

 

im hitting 19 with my cooler weather in Minnesota too

 

^^wat do u have done.