I just installed a CA header, XTC downpipe, and magnaflow exhaust. It now seems like it has actually hurt performance and fuel mileage. Also at full throttle i hear a sound similar to whoosing air from the passenger side. Can anyone help me?

 

lol! wow, you actually bought a shorty header... your first mistake....

you have a leak??

 

Odd. I have a CA v1 header, XTC 2.5" de-cat downpipe and an ARK N2 cat-back. But mine def made a noticeable difference in power in a positive way. Mines always had a slight hiss since its cat-less....the hiss is a bit more prominent these days b/c I need new exhaust gaskets (I did my full exhaust install back in Nov. '06 so the gaskets are over 2 years old...and I have 58k on the car). Maybe your ECU just didn't like it for whatever reason. A simple tune might be all you need. But I mean typically a full exhaust setup shouldn't hinder your performance, un-tuned or not.

 

i retained the cat and i checked the bolts between header and downpipe they are tight. If the header gasket is leaking will that create a hiss and decrease in performance?

 

A hiss...maybe....but a decrease in performance.....no.

 

Any exhaust leak can take away performance a bit. So its very possible.

 

Cat sounds clogged to me

 

I'm going back under the car this weekend to check the header bolts. I hope it is just a few loose bolts cuz i love the sound just wish it wasn't acting like it was hitting a brick wall at WOT. I know i do need a tune as i am still on the stock tune. Just waiting to find a good place to do the tune for a good price.

 

If he installed a full exhaust system (header, downpipe and cat-back) and is experiencing a small leak, he'd still have performance gains and should be able to feel it.

Plus, a "hiss" like leak isn't gonna hinder performance. If he said his car now sounds like a bulldozer, which means he has a full on leak, then maybe it might hinder performance.

 

Downpipe with highflow cat is brand new....shouldn't be clogged already. Its only been on a week.

 

The hiss will not decrease performance enough to feel it, if any performance is lost at all. Do you have an aeroforce or wide band to check for possible retarding from knock or show you are lean?

Also I installed my header and it was tight all the way around, drove and while its hot tightened more. Still had a hiss.. It took 3-4 times of barely tightening to stop the leak. Just keeping tightening being careful not to order tighten. Aluminum block and steel bolts with fine threads dont mix well.

 

exhaust too big for your mods. no fkn torque

 

Agreed ^^

 

Amen!!

 

not with a 2.5 exhaust. you guys are rediculous. I had a full 3 inch exhaust and intake and nothing else and it pulled like a ****.

 

the whole system is 2.5" i kept it that way because it is good up to around 300 hp and since i'm not putting that much power down i didn't need bigger. The hiss is what bothers me the most. A tune can fix my performance issues i hope i just wanted to know if anyone else had similar problems. No i don't have wideband or aeroforce although they are on my to get list.

 

300hp is still almost 100 more than the average stock ss/sc is putting down. you need a smaller pulley/injectors/tune to see benefits from a larger exhaust.

ever stop to think why GMPP catbacks are only 2.25"? optimal for stock pulleys

 

im always online late so you got to excuse some of my post.

 

stock exhaust is 2.5 so how is an aftermarket 2.5 that much different. Still doesn't explain the hissing at full throttle.

 

stock exhaust is not 2.5" the manifold collector is 2", the stock downpipe is at most 2.25" at its narrowest points (flex pipe and o2 sensor), and the catback narrows to 2.25" at the rear axel. the only 2.5" part is the mid pipe.

just man up and get some sorta stage kit

and it is common to have a hissing or "woosh" noise with a catless downpipe and header. check for leaks just incase.

 

I don't have a catless downpipe I have the XTC 2.5 in. downpipe w/ highflow cat. Stage 2 is on my list of mods and i have sportlines waiting to get installed. I just want to make sure the hissing is normal and not a leak.

 

Does anyone have a fitment problem with the XTC downpipe? Mine is off the the side and hangs so low the resonator scraps over speedbumps. Should I put the stock downpipe back on?

 

You should run the car so it gets hot then go back in and tighten the nuts on the studs. Make sure you tightened the O2 sensor also. Did you disconnect the large crankcase hose from the valve cover? It may be leaking as well if it is not tight. Just a few things to check.

 

Check the header and down pipe for a clog I know it is new but did you check to make sure there was no packing material from the manufacture inside of the new parts, could be those stupid ass peanuts they package with stuff also did the ports line up correctly with the header or did the gasket match the ports on the engine and header. Sounds like a block somewhere in the system.

 

Bump

Does anyone have fitment problems with the CA V2 header and xtc 2.5" downpipe w/ highflowcat? My downpipe sits too far off to the side of the exhaust tunnel and makes the resonator sit too low and causes it to scrap over speed bumps. I'm not even lowered yet. Should I put the stock downpipe back on?