Boost Fr33k

so i took my car to a good friend of mine because he has a shop, to install the gmp extruded honed headers and gmp catback exhaust.

i then get a call from my good friend asking me if i was sure i wanted to go through with it and this is why: the piping on our stock exhaust is close to 3 inches while the gmp is about 2.5 which is an obvious decrease in size. AND to his surprise the headers i have on now are exactly the same as the gmp"honed" headers. same numbers..everything.

as of right now, my exhaust is louder which is good. but i just cant understand why the gmp piping is smaller in size and why the **** r the headers the same!

any1 else have these headers??? maybe the guy who had the car before me had bougt the gmp header??

elmstreet

They headers are not the exact same although it is possible that the person before you purchased the extruded honed manifold. The stock exhaust is mostly 2.5 and the gmpp exhaust is 2.25

silverSS

you are referring to the manifold, yes they have the same part # on them because they are the same manifold just honed out a little bit. IMO a waste of money.

Also with the exhaust..our stock is exhaust is 2.5" not 3". The GMPP cat back is 2.25 but has a less restrictive muffler. IMO again, who would go with a smaller pipe? So in all, you are correct. you bought smaller piping with a less restrictive muffler, and pretty much the same manifold.

Boost Fr33k

yeah i knew my friend was just giving me an idea with the inches i knew the piping wasnt 3" and that "honed" ****, makes sense now.

cobi

The header is the same cast manifold but the inside is Extruded (enlarged) and honed (smoothed). Its not much different from stock but is better and keeps warranty. Also the stock exhaust necks down to 2.25 just before the muffler. There is a dyno proven 12 hp increase of someone on here the difference is the free flowing muffler, not pipe size.

R&C_rallySS

Well everyone I know who dynos sees results. Some many people think bigger is better. In most cases it is better to have smaller exhaust then 3". Most cars with 3" exhaust see great results because they have 350whp+. Anything before that does nothing extra. I have seen it time and time again on the dyno. You made a great choice with the GMPP. I gained better times in the 1/4th with my exhaust and intake for sure.

P.S. Any chance you could get a write up on how to install the GMP header. I have been having a few probs with it myself.

Boost Fr33k

yeah i read some forums here about how supercharged engines under 300hp dont really need anything bigger than 3" piping. about the headers, my friend told me it was a exact fit, no new gasket or studs REALLY neccassary. although there is a lil hissing noise WOT :?

performance wise, i did feel a new kick. soounds good though. gotta brake it in though[smelly]

cobi

yah i have noticed that same hissing noise when you get into the throttle since day one

D4u2s0t

the "hissing" you hear is just the extra air passing through...

syP

smaller exhaust = more lowend


i noticed a nice kick in the ass when i got my GMPP exhaust installed.... i hear 10-12hp gains???

Boost Fr33k

thats what they say! some kid got a dyno and saw 12hp but i gotta see for myself. ill be getting a dyno somewhere near future. ill deff post it up