question about exhausts

[audi-tone]

hey fellas, currently i have installed a 2.5" downpipe and an aftermarket rear muffler. i like the sound but am wondering if i'll see/hear a big difference if i get the rest done in 2.5" piping? from what i've read having different sizes in an exhaust isnt the best thing to do, but i'm worried its going to be heaps louder?!?
cheers

[Manaz]

Bigger centre pipes will equal more noise, but you can deal with that using mufflers/resonators.

[McDub]

i hear it's best to have it larger at the engine/turbo (downpipe), and as the exhaust gases cool, too keep the flow rate consistent you want the piping to reduce in diamteter... basically means an aftermarket downpipe + cat with stock exhaust should be all you need for the gti in terms of performance...

btw, i have a billy boat exhaust on it's way, will get a before and after video of the exhaust sound...

[Speed]

hey fellas, currently i have installed a 2.5" downpipe and an aftermarket rear muffler. i like the sound but am wondering if i'll see/hear a big difference if i get the rest done in 2.5" piping? from what i've read having different sizes in an exhaust isnt the best thing to do, but i'm worried its going to be heaps louder?!?
cheers

I was told I'd only get about 8 hp with a full 2.5 inch cat back system and more noise.

I don't think its worth it. The downpipe is enough, so your sorted.

[audi-tone]

well i actually ended up getting it done today and it has made a difference in noise and power. feels less restrictive and i feel it revs quicker so i'm quite happy. was only $200 so i thought i may aswell do it. i had a nagging noise that i thought could've been the wastegate rattling but since doing this i believe it might have been the airflow out of the cat or the middle resonator could've been bad because it spools louder (obviously) and the noise it was making is gone.
i'm happy with the results.
thanks for the inputs fellas. one step closer to a stage2 remap. next on the list, 4bar fpr.

[JustCruisn]

I was told I'd only get about 8 hp with a full 2.5 inch cat back system and more noise.

I don't think its worth it. The downpipe is enough, so your sorted.

You get more like 8-10kw or 10-14hp. Fairly sure most of this is due to the DP. I run 2.5 turbo back + highflow cat to the stock muffler and have +9kw ATW.

[Speed]

You get more like 8-10kw or 10-14hp. Fairly sure most of this is due to the DP. I run 2.5 turbo back + highflow cat to the stock muffler and have +9kw ATW.

+9Kw ATW Interesting.
But like you say, most of this is due to the downpipe.

Where did you get your DP?

[JustCruisn]

+9Kw ATW Interesting.
But like you say, most of this is due to the downpipe.

Where did you get your DP?

I got mine for a bloke on the forum, he was replacing with a Remus or something.