certz

At the Watkins Glen CR this past weekend, I was talking with Jeff from Kelly Motorsports about exhaust systems and that I wanted to delete my Cats now that the car is track only. He said they (KMR) are using 997 Cup Car mufflers for the basis of their exhaust systems on race cars. Basically, they run the headers to the inlet of the muffler and done. He said the mufflers run about $600-700 so a formally $4,000 plus exhaust becomes much cheaper. I know the cup mufflers have center exhaust tips so I would have to do something to accomodate that, but I was wondering if anyone else has done or seen anything like this.

Bill Verburg

That may have been Jeff Gamroth from Rothsport, he was there co driving the KM 993

This is a typical GT# muffler setup for a 993, don't know how that would work w/ stock 993 headers



I like separated cat bypass pipes to stock or modified stock mufflers, it keeps weight out of the extreme rear of the car and is reasonably quiet

hard to ee but there are 2 separate flow paths, it could be made a little quieter w/ an H pipe between the 2 as seen inside the side mufflers


This mod to the stock 993 muffler, wrapped w/ ss and or cf and or f/g flows best


This is a stock 993 muffler, which just dumps into the can and as a result losses some flow efficiency

jscott82

Any noise restrictions? If not, just get rid of it all..

Picked up a little HP, and only cost $300... but it is very loud.

https://rennlist.com/forums/showthre...ferrerid=45114

certz

Thanks Bill - are those the old style Fabspeed Cat-bypass that were separate pipes? It is possible is was Gamroth, but I missed his last name. He was talking with a buddy that has an old KMR built race car - a 964 chassis with a 993 WB fiberglass kit. He remembered building the suspension, modifying the roll cage, the engine build, etc. from 1998 when the car was built.

Jscott - I thought about that but I am concerned it would be way too loud. Of course, I hear so many cars that sound like they are putting out 150 db and not getting called in, so maybe it would be fine.

trophy

The GT3 Center Muffler won't work with stock 993 Headers, you will need at minimum a set of headers that has as big as possible distance between the header outlets. The GT3 Muffler is about 30" wide so the headers need to be wider than that. For most you need a really good exhaust guy and a set of headers like Fabspeed, S-car-go, Rothsport etc.

Joe@Fabspeed

Yes those look like old school Fabspeed Motorsport 993 catbypass pipes "over and Under style" with a Bischof flange. Yes a big performance gain all across the RPM band but very loud.

I like the picture of the 993 headers with 2 pipes coming directly off the factory headers directly center out GT3 style. THAT is 100% the loudest possible exhaust for these cars and comparable to long tube headers with short RSR straight pipes aiming out each 993 rear bumper cut-out. In fact the long tube headers with straight pipes that would be Quieter than the factory headers with straight pipes.

You cant really make connection pipes to allow the factory 993 headers to be bolted to a 997 GT3 OEM muffler as the exhaust pathways would be ridiculous. I could do it but the car would fall on its face

I have DYNO developed Fabspeed Motorsport 997 GT3 style replacement mufflers that outperform (+7HP more than stock 997GT3) and are stronger 997 GT3 OEM Porsche mufflers are cracking and breaking its public domain.

I was going to mandrel bend everything but assumed the marketplace is miniscule as no one wants to CUT a big hole through their 993 rear bumper cover as you can get the same or more power with proven exhaust systems that allow the exhaust to come out the factory 993 left & right existing bumper cutouts. Yes it looks cool and if someone brought me a car I could digitize everything in TEZET CAD and download it to the mandrel bender and make systems.

Another option which would eliminate cutting a 911SC/3.2, 964, 993 rear bumper would be to design the system in a Y pipe with resonators or use a Fabspeed 997 GT3 center out muffler and have the center out pipes RUN underneath the rear bumper cover. Club racers and others have done this for years.............but you have to be Gung Ho and you lose ground clearance on street driven or dual purpose cars.

Once again its car customizing, verifying power , and costs. Fabspeed Motorsports USA a Rennlist long term supporter advertiser can provide everything for any of these aircooled projects.

If you really want to I can use my ANDIAL built 993 RS CS clone break out the ROMER arm laser scan and digitized everything.............remove my rear bumper cover or send me a rear 993 bumper cover and come up with a great light weight cost effective system.

joe Fabiani president of Fabspeed Motorsport USA PCA club member since 1986

Bill Verburg

Yes, I think they call them crossover design, FVD and Cargraphic still carry them.