Graham L

Hi – is anyone on here running both a primary and secondary bypass? I’ve done the searches etc and found a clip of some guys in the US (possibly from FabSpeed?) doing a demo of this set up, but cant see if anyone is actually doing it. Found loads of other combinations as clips (including mine when it was std – now got secondary b/p).

I don’t need it for track days so noise isn’t a principle concern from that point of view…

Anyone?

Computamedic

Graham,

As far as I understand it, using both primary AND secondary bypasses would amount to having NO silencing at all - in other words, bl**dy LOUD!!! I remember at one time the garage I bought my car from had cause to start the car with no silencers attached and the noise knocker their clock off the wall!!! I can't imagine the car would be usable on the public road making that sort of noise. I suspect the performance would suffer too since all back pressure in the exhaust would be eliminated.

Regards

Dave

Euromagination

Wow, that would be crazy loud. I have just the primary bypass and it's pretty loud as it is.

Go for it! If you don't like it, sell it to a Rennlister. Pretty easy swap-out.

-Harry

OllieW

I've got a cay by-pass and primary silencer by-pass on my 964RS but have kept the last secondary silencer as it is too loud without it. I think Dave has a valid point about the performance too as back pressure will be almost non-existant.

Do you want to stay friends with your neighbours?

Graham L

I was thinking along the same lines as Harry - ie i could always sell it on to someone later. re back pressure though: didnt cup cars run primary and secondary b/p? As regards to loud - i dont think the secondary makes too much noise, so more would be more 'dramatic'...this probably means that either i have become completely immune to exhaust noise or the secondary has made me deaf and now i need more!

Is it really THAT bad?

garrett376

I run a cat bypass, a hollowed out primary muffler, and a secondary bypass. It is VERY loud. I would assume my car would be a tad quieter than if I had a "real" primary bypass. Here's the thread with a sound clip/video of the car - super loud!

https://rennlist.com/forums/964-forum/218771-cracking-the-primary-muffler-and-turning-it-into-a-beast.html

GG Allin

I ran both bypass pipes for a short time. The car sounded literally like a pack of Harleys with open pipes. It was too much.

Geoffrey

The removal of the "suitcase muffler" is 8rwhp over running with the muffler across the range. Without it the car is quite loud.

Graham L

Garrett - i cant view .mov files so cant see your clip, can anyone get this in another format for me please? it sounds like you've got the closest thing to what i was thinking about. Nice to hear that the potential lack of back pressure isnt causing you a problem.

Euromagination

The suitcase muffler is the secondary one, right?

Which shows bigger gains when used on their own? The primary or secondary bypass?

NotTwinTurboYet

I had the cat bypass, primary bypass and sport exhaust (coming from FVD) replacing the secondary muffler. It was very loud over 4'000rpm, but soooo good!
Whithout the secondary muffler it is definitly too loud, impossible to drive with that noise.

A+

kusee pee

Graham, go for it - I'm about to do exactly the same. I'm pretty happy with the noise with just the secondary bypass but as far as I'm concerned the more noise the better. In fact, the noise was THE most important reason for me getting a 964 in the first place! Let me know when yours is done and we can compare!

agentpennypacker

I really pissed off my neighbors by doing this - it was VERY loud at idle.

I would stick with one muffler and swap out the cat. Plenty lound, gain some power, etc.

kgorman

This thread has tons of info on the subject.

https://rennlist.com/forums/964-forum/229566-muffler-bypasses.html

Graham L

... thanks for the link . nice to see that Greg's comparison of exhausts is in loads of threads!