john d 81SC

Just bought an 88 Carrera. It's been suggested that I add a cat by-pass, or I add a Euro pre-muffler. Please explain the differences and which would most improve performance. Thank you in advance.

84_Carrera

Same thing, basically. I have a Fabspeed Euro Pre-Muffler on my 84.



Here's a stock-style replacement Cat:


This is a typical "bypass / test pipe":


The 1st & last accomplish the same thing, basically - remove a restriction in the exhaust. If the cat's partially plugged, replacing the cat with a new one will also help things out.

BHMSC

I have one on my '80 SC and have been pleased. It's really a nice piece of work, enhances the sound a bit (not too much), and they claim a small power increase (7-10hp, but I can't vouch for that).

My car is now "historic" so I don't have to get the emissions tested. The rumor is that SCs will pass the Maryland emissions test without a cat but I never tried it. Check the emissions situation before spending the $300 with FabSpeed.

ron mcatee

I removed the factory Cat from my 88 Carrera and put on a Bursch test pipe. It installed easily and did the job. The only drawback is that it had a very noisy resonance from 55-70 MPH. A friend suggested I get a euro pre-muffler and try that. I bought a Fabspeed euro pre-mufler and the resonace went away. I would recommend the euro pre-muffler over the standard test pipe for the resonance. GHL, Fabspeed and others make the euro pre-muffler, so it's your choice where to get one.

84_Carrera

The Fabspeed is essentially a small resonator, and is a really nice piece of eye candy. Right now I have that & the fully-polished M&K on mine.

Jay H

I've got a Dansk Euro pre-muffler on my '84 Carrera in place of the cat. That pipe with the Dansk sport muffler choice is a great upgrade for how the exhaust sounds. I doubt there is any increase in power. My exhaust looks great, sounds great , has no resonance at any rpms and are well build pieces.

Jay
90 964
84 3.2

Diamond Blue

I have the Dansk euro pre muffler along with a custom SteveW chip. www.911chips.com If you don't have a Steve Wong chip look at getting one. Do a search on "stevew or performance chips" Many happy customers. Would make putting the euro-pre muffler on even more worth while. Better drivablity and performance

rnln

What is the test pipe to be exact? Is it a straight pipe without resonator?

Anyone know what the inside of the Fabspeed and Euro pre-muffler is? Is it the honeycom type as the cherry bomb none directional or is it like the directional spiro resonator?

Can someone comment (with personal experience) on gain or lose?

btr4me

Certainly every car is a little different but I ran a chipped 88 with bypass pipe through emissions and it passed with no problem. I wouldn't let them run it on the dyno though and I chose to go at a busy part of the day, which let the engine get nice an toasty while I waited in line (I figured the hotter the better).

Corrales911

I got a bypass pipe but no unusual resonance. My only beef is that the flange bolts keep getting loose - prolly more to do with reusing the old bolts and not the pipe itself.

BHMSC

The inside of the FabSpeed looks like an old-fashioned cherry bomb. You could probably roll a golf ball through it. It's not just an off-the-shelf cheapo part though because the whole thing is T-304 stainless.

rnln

Thanks BHMSC

DPDISXR4Ti

Keep in mind, technically, if you remove the cat and replace it with a bypass/test pipe/pre-muffler/whatever, you are committing a crime, regardless of what your state's emissions laws are. It matters not whether you can pass a sniff test or not. I'm not trying to be a tree-hugger here - just stating facts so you can make an informed decision.

So from a practical matter, go with something that can at least represent itself as looking like a cat.

BHMSC

I actually worked on air pollution issues for EPA long ago (when it was first formed). It is true (as far as I know) that removing the cat is illegal even if you meet the sniffer standards and the test stations are also supposed to do a visual examination. I've dodged the problem by switching my car over to historic tags (thus no test required here).

Although I support much of the "green" agenda, I took the cat off my car so I guess I'm a hypocrite of sorts (aren't we all). In my mind, at least, I can rationalize it in the whole scheme of things since the car has only accumulated 30,000 miles in the 14 years I've owned it.

84_Carrera

Personally, I support the whole "keep your car tuned up" philosophy. Funny, my '74 Rocket 350 (5.7L) engine in the '80 Cutlass I had with NO smog crap on it passed much better than the old tired 4.3L V8 it originally came with, and that one had all the smog garbage. Want to keep it clean & green? Keep it tuned & running well, use the car for commuting & trips & walk to the corner store instead of driving 500 feet. But hey, I'm a scofflaw anyway.