chancecasey

Anyone have any experience with bypassing one or both mufflers? I was checking out the fabspeed web site - and while I'm not about to pay $1000 for a muffler or $350 for a few feet of pipe, it did get me wondering...

They claim their primary muffler (which presumably is a "better" primary muffler, and forces you to not use a secondary muffler) alone nets 15 HP which I'm pretty suspect of. I would think most of the advantage is just bypassing the secondary muffler, which you could do with a piece of pipe and the stock primary muffler.

Just wondering if anyone would care to comment about:
1. just how much backpressure mufflers really create in the first place, compared to say the cat - and how optimistic 15hp sounds in the secondary bypass example
2. somehow i don't think it's as simple as removing backpressure - wouldn't you need to compensate with some DME modification (e.g. - new chip)
3. how LOUD would bypassing the secondary or primary muffler be? I know certain tracks have noise restrictions - and was wondering what muffler bypassing, if any, some of the more "tracked up" cars have - and if there is any noticeable power difference - "seat of pants" or otherwise measured.

P.S. - Any recommendations for a low-cost cat bypass?

Chris M.

Unfortunately I don't think there's a low-cost anything when it comes to these cars.
Anyway, many people have done all kinds of bypass variations with different results. Tom W. (of the 993 and 964 boards) has done some experimenting with Fabspeed products and would be a good person to ask. As I understand it, the secondary bypass adds a nice growl to the exhaust but is not too loud. This pipe is also called a G pipe and can be had for around $150.
Here's a link to some videos by a Rennlister in the UK comparing some different exhausts.
http://members.rennlist.com/greg_l/964ex.htm

enjoy,

c

chancecasey

Thanks for the tip, Chris!

I realized when searching the forum I was using cat bypass emission, and then my mind wandered over to muffler bypasses - which I did not do a search for before making this post. Sorry. I'm still reading the existing threads on this which seem to have all the info I'm looking for. But if anyone has anything extra to add - feel free - and again, sorry for the redundant thread here.

Chris M.

No worries about the redundancies. Just don't bring up the undertray! Only kidding.

c

chancecasey

where did you find a g-pipe for $150? I can only see fabspeed's at $350 which really makes me nauseated considering it would cost about $25 if home depot made hi-temp chrome pipes for the ****ter. Almost makes me want to send off a CAD file to a stereolithographer, create a mold, and do a small fab run. Unfortunately I only need one.

Anyone else know of a cat bypass for under $375 while we're on the price topic?

After reading the threads related to this, I think cat and secondary bypass sound like the way to go for my needs (mostly street). I did not notice a huge sound difference when I ran with my secondary disconnected - but that was with the cat on. Also sounds like this setup (cat/second bypassed) yields the best bang for the buck HP-wise while staying legal for tracks in Northern Cali.

Jeremy Pinsly

From what I understand, replacing the primary exhuast with a bypass will yield HP gains, which will come at the upper end of your powerband. Replacing the secondary exhaust witha bypass will yield more torque, which occurs in the low to mid range of the powerband.

For track use, you will probably be running the engine close to redline most of the time, in which case you will be at peak HP. In this case, it will make sense to have a primary bypass.

For street use, you will probably not be running at redline all the time. It makes more sense here to use a secondary bypass because you will be operating in a more useful portion of the powerband curve.

Others may have different opinions.........My 0.02.

GG Allin

My car has the secondary bypass, at one point I had both bypassed. The car was way too loud. It sounded like a pack of Harleys with straight pipes, literally. I've heard 964's with the primary bypass, they don't sound much differant than my car. As far as cheap goes search "porsche bypass" on ebay and save the search. These pipes come up on there all the time.

pete000

One nice side effect is the loss of a few lbs out the tail! I have read a lot about the 100 cell cats and they sound like a good street alternative to the cat by pass. One problem Price!

Euromagination

I have the RUF primary bypass and I think it sounds awesome. It gives the car more of a raw gurgle at idle too. Sometimes a little too loud though if you give it more than 75% throttle--and it really screams (very loud) above 4500rpm with full-throttle. Went through a tunnel with full-throttle once and swore I was driving a race car. LOL.

Oh, and I have to add... On the highway in 5th gear @ 60mph, if you give it a good amount of throttle to make a pass... it sounds even better than stock... one of my favorite sounds of all time!

HP gain? I don't know numerically, but on the butt-dyno it seems to have slightly bigger lungs in the high RPMs than without the bypass.

Smile factor: High.

Tom W

My car LOST 10 hp when fitted with Fabspeed headers and dual outlet muffler as compared to a Fabspeed cat bypass, stock primary and secondary bypass. Joe did honor his deal and refund the money as it did not make 20+ hp as desired/promised (and the headers were beautiful, they just didn't provide what was desired).

I found the best bang for the buck was the cat bypass and the secondary bypass. It gave a good hp gain, was cheap, and meets the Nor Cal track sound restrictions. Most important, this combo gives 89 db and meets the 90 or 92 db restrictions at Laguna Seca. It's legal to do this for track use but not street legal.

My new engine is on an engine dyno right now and we are getting some numbers for it comparing the cat bypass and secondary bypass to another system. I'll be able to post results next week.

I think the secondary bypass makes for a more throaty gurggly sound and the cat bypass increases those effects.

pete000

I jusd did a serch and this came up $149.00 for a secondary bypass.

chancecasey

Looking forward to the next set of REAL data - we all owe you a cold one for these tests!

pete - thanks for the g-pipe link!

mark lintott

I have the sports cat and primary bypass with stock secondary. Sounds great and certainly feels more energetic. I tried the sports cat with secondary bypass and stock prmary but the other half kicked up a fuss over the noise - it was slightly louder but not much so I'm back to primary bypass and cat etc.

My secondary bypass was a Dansk for avbout 150$ US and the primary bypass is a Sportec approx 300$US the sport cat is also Dansk but I don't remember the cost. Make sure you get one with the oxygen sensor outlet - some straight thru "cats" don't have this.

Schuey

sweet, it'll be great to see this...

Christer

Forget it from a performance point of view, but if you like sound....go for it!