EighTT

Does an aftermarket cat-back exhaust (only) really add extra hp or just sound cool? Evidence?

Jason Chen

It does add ponies, but not as much as a downpipe and freeflow cat does.

Bluto

well except for a chip. Really what other mods add substantial hp across the entire performance spectrum when run on a Dyno? Better acceleration, more linear response and things of that sort are what most mods (IMO) give the owner. Now in the case of an exhaust if it is designed properly, should provide better flow of gases out of the engine and then for make the car breath better and perform better. Add extra hp, I guess so but in my case I am thinking that if I add an exhaust exhaust flow may be improved and any "backup" of flow that may be causing my wastgate to prematurely actuate may be removed thus helping my turbo perform better.

HP gains attributable to the addition of an exhuast? If my theory is correct then yes, but only because it is helping to resolve a problem. Anyone want to confirm/deny that theory for me???

Oh they do sound cool too of course.

joe@vwvortex

since we have a dual setup and twin 45mm downpipes.

joe@vwvortex

The biggest restriction on the TT is where the exhaust goes under the haldex - it's crimped to under 40mm! My Jetex is 70mm all the way back into the muffler as is the Forge (although there is some very minimal crimping on the Forge. I'd say you'd pick up 7-10hp easily with a good 70mm exhaust or bigger.

JustJeff

Whether you attribute this to just allowing the turbo to spool more freely, or that the free-flow exhaust system actually turns this into more HP, don't exactly know.
All I know is that it gaves me a better kick in the butt, across certain RPM ranges.
I call that extra HP.

ND4SPD

or AS important? Why do people go with the single 3" then?

JazziTT

I agree 100%. Milltek exhaust makes a difference.

JazziTT

The OE cores can melt.

The Pope

Gtech data. Each mod done seperately. Quite interesting to see the results.