Turbo Jonny

I met a 3.6 owner at a show recently who had a cat bypass pipe made by porsche.As this is my next upgrade job i checked with my OPC to order it but they only found a non-turbo 964 one listed.Any one know of this and maybe have a part number? Also is the Euro Cat the same as the US and yeild the same performance increase? Cheers !

Staffan

Never heard of a cat by-pass from Porsche, perhaps from Porsche Motorsport or for cars on markets that didn't have that strict emission regulation. There are a number of after market vendors, Fabspeed, Cargraphics and others. I found an empty cat on Ebay got it for $150 usd.

911addict

John,
As you know, there are various aftermarket bypasses (for both the cat and the silencer) but never heard of Porsche parts.

That said, I wonder what the 3.3S had, did it have a full Cat? And what about the Flachbaus?

BTW John, as a 3.6 you'll not be legal in the UK with a Cat bypass, you'll need the 100Cell cat. There are lots of good threads on exhaust mods on this forum if you do a search.

eyue

I had the Fabspeed Cat-by pass on my 3.6 turbo. The engine sounds more deep and a little quicker on response, much more driving pressure for me.

Turbo Jonny

911 Adict ; It was Gmund Cars who said it was a porsche part.I will get to the bottom of this if i can! As to legality the owner i met with the bypass ( it sounded nice ) claims he has no problem at MOT. I think i will risk having to change it if it does fail.

Anyone ; should i expect c25bhp increase with removing a UK cat ?

911addict

Don't get me started about Gmund Cars!

Staffan

I have a german car, don't know the difference between UK cars if any.
The biggest advantage IMO is faster spool, the numbers on increased hp is more like 15hp at least that's the dyno numbers I have seen. Overall well worth it in my oppinion.

Combined with removing the muffler the sound gets great, the maximum db doesn't increase since the wastegate pipe is producing most of the sound (not going through the turbo). I am at 95db when driving on the track, that's where I was before removing the muffler.

911addict

Staffan,
let me get it right, you are running with cat bypass, muffler bypass and wastegate bypass and its just 95db? How does it sound at idle, high revs, and turbo boost? Any chance of some soundfiles?

riverflyer

Yes, I have to wonder how that could be. Last time I was at the track there was a car with similar setup in the run group on track and every time he went by, you could hear nothing in our drivers meeting even with all the windows and doors shut. AND the building rattled!


eyue, in your post you said "much more driving pressure for me". Did you mean pleasure or were you refering to back pressure?

Staffan

I should say that I could be wrong about the 95 db, but I don't think so.
Have been running without muffler on several track days and so has Vincent on this forum, they (Porsche Club Sweden) are very concerned about sound and Vincent is one of the instructors, I am sure they would have told us if he or I have been too loud, they do send people home on a regular basis and being an instructor doesn't make any difference. But, I guess it could be that we have been lucky with wind direction and such, unlikely though.
95db is the limit on these meetings.
Have to say though, that I bring my muffler to the meetings just in case.

Think about it, the wastegate pipe is a straight pipe without muffler and the exhaust is not going through the turbo. The turbo makes a great difference chops the sound waves. Could also be related to that I have en empty cat, not a straight by-pass pipe, but I don't think so. I know Vincent is running a race cat.

The shape of the exhaust tip makes a great difference, once I was running without one on the wastegate side and it was EXTREAMLY loud. Could be that the loud cars you have heard had an aftermarket exhaust system or exhaust tips.

About the sound in general, it's much louder at idle and in general.
The sound is great, very powerful, a head turner for sure.
When the car idles at my drive way my house is vibrating, just so you know.
From a "feel" perspective probably the best mod I have done, and this car is far from stock.

I have been standing just by the straight comparing the sound between a 964 turbo w/ muffler and /wo muffler at full boost, couldn't tell the difference. Didn't check the sound gauge at the track though.

911addict

Staffan, please remind me which make of exhaust mods do you have?

Staffan

I run stock headers a stock but empty cat and a Cargraphics muffler by-pass (just a u-shaped thing), rest is stock including exhaust tips.

eyue

riverflyer, my typing error, I mean with thr cat by-pass, the car seems to be alive, less turbo lag and sound more like a Porsche....

riverflyer

thanks for the clarification. I had straight pipes on a fcar for awhile and though they sounded great, the smell, especially when cold was bad and I felt bad about polluting more. I have since switched all my cars to high flo cats and that seems to give the same response, improves the sound and still cleans the emissions.

Can you post some pics of your car, looks great.