tlark

Does anyone have any recent actual Dyno numbers of the Fabspeed muffler by-pass pipes. Kevin, Bob or Kasper, anyone..........a pair of used ones are for sale over in the classifieds and a 30hp increase statement was made. I find that real hard to believe and always wondered !

ca993twin

I have no numbers. I agree that with a stock TT setup, you're not going to see that sort of HP increase. I wanted to add, however, that the bypasses are good for other things as well... nicer sound (subjective), a big weight savings in the ***-end of the car, and better air flow to the turbos and heads. What else have you done to your car (engine-wise)?

viperbob

On a stock car with the factory cats, we have seen 10-15 HP gains. No where near 30 HP. While the gains are reasonable, you will also find that the boost comes on sooner with less exhaust travel, back pressure, etc. You also save about 50 lbs on the rear end of the car without the mufflers...

Basal Skull

yep, about 14 net Hp according to my G-tech pro with my home-made bypasses

tlark

Thanks guys, thats pretty cheap HP gain when you think about it. I think they go for around $550 new, if I could spend another $500 to $1000 and pick up 25-30 HP I would do it. Are cat-bypass pipes the next step ??

ca993twin

Tom,

Cat Bypasses are generally good for a bigger HP gain than muffler bypasses. When used together, they sound pretty damn loud. Its a simple swap for the muffler bypasses, quite a bit harder for the cats bypasses. Cat bypasses are generally much more expensive ($1500-$1800) and illegal (if you worry about that sort of stuff) in most states. No... the next step would be some 100 cell racing cats... large diameter ones like Kevin sells are probably your best bet. This will be reasonably loud... but tolerable. I use 100 cell Ruf cats (I don't know the diameter) with muffler bypasses. Pretty damn loud at cold start, but then mellows out after a short time.

tlark

Thanks Steve, I have considering installing some type of cat by-pass system, my kids love noise, wife thinks I'm already insane so it doesn't matter.

Its snowing its **** off here, 10" by morining so I'm having major withdrawl and brain storming about what mad scientist things I can do over the winter.

Bill P.

Hi Steve,

I use muffler bypasses now. Would adding the 100 cell cats add to the loudness or would it be about the same??

Thanks for the input.

Bill

PorschePhD

Tom,

18 max. That is HP in 2WD and 24 in AWD. Just depends on how the numbers are being quoted I guess. The noise is not bad and for what you do with the car any release of back pressure is good. I would however advise against cat bypasses. The system will not be happy (ECU) and may or may not react to them being gone.

Ezzy

Is the bypass a replacement for the cat/muffler or an additional bypass pipe?

EZ

ca993twin

Ez,

We are discussing REPLACEMENT-type bypasses... the muffler bypass allows you to completely remove the mufflers (with all their weight, heat, and back pressure) and replace them with short pipes. Turbos don't need no stinkin' mufflers!

The cat pypasses replace the cat pipes with pipes that look like cats and even have a place to install the O2 sensors. They are generally sufficient to fool most smog "visuals". But the car generally will not pass a real smog test, there is a nasty fine (here in California, at least), and its kind of a pain to swap them out. Race cats are a fine idea, as they will generally pass smog and give most of the benefits of the bypass (using the info gathered on this forum) if you use the large diameter cats.

Each step along this path produces more noise... some find it objectionable, some like it. Its best if you can try before you buy.

Ezzy

Thats what I thought (replacement) - thanks for clearing it up. I don't have to worry about a smog test but because of climate it may be a better option (in my case) for a muffler bypass to keep it cooler. Future projects . . .
EZ

ST

I had the by passes on and they worked great..definitely faster spooling up of the turbos and therefore better response to the throttle. The extra noise is not too bad, louder on start up but once you get going it is fine. Then I had a problem with my cats and since we do not need them here in malaysia, i had the cats cut up, hollowed out and welded back together...definitely can feel the kick of more horses and a lot cheaper than a set of cat bypasses, but then it was a bit loud, so the mufflers are back on again.