RallyDogRacing

I'm thinking I'd like to lighten up the rear end a tad before I head to MidOhio for the AudiClub event. I also wouldn't mind having a track-type exhaust versus the everyday street version. Anyone care to comment on the best price option for primary and secondary muffler delete?

I'm awfully tempted to head over to my magic-exhaust guy and simply have him fab up a post-car straight-pipe that hopfully would even avoid the need for a J-pipe. I'm sure there's a reason no one does this so any education you'd like to pass on will be welcomed.

As far as the best price bypass pipes are concerned. I don't care who's name is on it, as long as it will seal up when mounted. Whether Ruf, FabSpeed, BB, GHL, or "John's Muffler World" makes no difference to me at all.

garrett376

Do it! It will save you a lot of dough, that's for sure. The hard part about fabricating the stuff is most muffler shops around me don't have very talented guys, or they don't have equipment to bend 2.75 or 3" tubing. Doing a 90 degree bend on 2.75" tubing with really tight radiuses just doesn't work well on the crummy equipment my local exhaust guys have. That was the problem I ran into when I fabricated a custom system that I eventually ditched. I think that is why people fork out so much money for the already made systems - most poeple I don't think, know someone that can do that. If you have a good exhaust guy, and he's got a large enough bender that can make tight 90 degree bends - you'll be set, and save a lot of money! You just need to go from the cat, to the tail - no reason to even have a different tailpipe - just use the exhaust tubing. Hey, if your mechanic will make a spare pipe to go from the cat to the tailpipe, I'll buy a pipe, too!

RallyDogRacing

Cat outlet to stock pass side exit point via most direct method yes?
2.75-3.00ID Mild steel (cheap-o track exhaust)
Stock type mating flange to cat
Mounting flange points to hang at body attach points.
Slash cut tip for that neat-o look
I'm thinking everything but the cat-mating flange is a slam-dunk. Jimmy @ RobinHood (old artisan dude) should be able to knock this out. I think I will go see him next week if someone doesn't tell me where I can get these pipes for the $100 each that they're worth (that's still a rediculous mark-up over costs) I'm sure if Jimmy can build one, building two is just as easy. I'll keep you posted.

Here's another bizzaar idea: why not simply dump out of the cat via direct short pipe and point it down at the ground at an angle greater than 45deg? The would offer very little restriction beyond whatever is introduced in the cat, but would gain you noise-harshness cancelation effect of the ground surface. Also it's even lighter... I personally like to leave the cat in place if the system has tubing beyond the cat location because of the change in flow behaviour toward a more laminar state, not to mention it's also an effective muffler.

jimq

isnt that where the O2 sensor is also!

Tom W

To what gain other than noise? My dyno data showed that a fancy header and muffler did nothing for power, it just made the car louder. You should consider a before and after dyno run to see if it really gets you any benefit. (My car normally has a secondary bypass but the stock primary muffler.)

RallyDogRacing

My intention is weight reduction, and admitedly more noise just for the track.

Jim Michaels

Then bypass both. You'll have less power, but a lot more noise. You should check that you will still be under the noise limit for the track, if the tracks you run check for that. The recent wisdom passed around is that the primary muffler bypass will give a few more hp, and the secondary bypass a little more torque. But if you bypass both, you get a little less power and weight, and a lot more noise.

fstockcarrera

wrong... By pass both gives more power, noise and less weight.

No recent wisdom here, just dyno time! Fabspeed euro pre muffler, primary by pass and secondary muffler is a good set up for tracks that have some noise restriction. Loose the secondary muffler to gain 9 rwhp. Dyno tested.
Bob
1990 964 track only

N51

Hey Bob,

Took your advice and have the RSA set up with a primary bypass with the euro premuffler + the cup airbox. Sound is very muted until you put your foot in it. A perfect set up for my long distance driving. Thanks again.

Noah

garrett376

Hey Guys - does the euro premuffler have baffles in it, or is it straight through like the other bypasses available?

Bob, thanks for chiming in about the dyno findings. There are often rumors about what works - but I had yet to come across anyone who actually dyno'd a full open exhaust like you did.

agentpennypacker

Did you guys also bypass the cat? I'm assuming so. If so, did this also help? I installed a primary bypass last night, and the car does feel a bit quicker. The original primary is VERY heavy.

Also, What kind of chips are you running with yours?

RallyDogRacing

All, just to be clear on my motivations; I like a loud exhaust at the track when running marquee car club events. The C4 in stock config doesn't need more power. Until I've got some telemetry telling me my average throttle position is well past 60% over the course of a run group then my belief is that I'm not using the power I have on hand effectively.

So why chase the pipes? Well it's a similar theory to having a loud exhaust on a motorcycle. People are far more aware that you are "around" when they can hear you. Peripheral vision w/helmets for most people is crappy. In general if someone is driving their mirrors then they aren't driving the track. Those people are dangerous. I want them to be able to hear me and have a decent idea of my position based on sound vs. having to watch their mirrors and screwing up their own line.

The second primary motivator I am driven by is weight reduction. It is far less costly to remove weight than it is to add HP & torque when dealing with simple things. Run the HP/# and TQ/# calculations yourself. Removing 65+lbs off the very **** of the car moves the Cg forward, reduces the polar inertia of moment, and has the relatively same effect of adding power. Were I able to go to a track exhaust, race seats, and a gell-cell battery for the days when tracking I am easily negating my own weight in the car itself. These are all items that are swapped in before heading to a track event, and the swapped out upon returning home.

For me personally it's a good dual-purpose management of the car. Your results may vary.

N51

RDR: Understood. And weight reduction was the main goal in my removing the primary and cat, but there is where our goals diverge. As a street car, this is an, IMO, excellent compromise in power, sound, and weight. I plan to try a secondary bypass with the premuffler, but not in conjunction with the primary bypass. Just too much noise on the street. My consideration for further weight reduction will center around the hood and tail, perhaps the wheels. The seats, cloth sport, are too comfortable to give up for distance driving, unless someone has convincing evidence of another LWT Recaro type seat that will perform equally well in this application. I may be interested in a 'J' pipe if you can have one quality fabbed.

Garrett & Agent': The euro premuffler is the cat bypass and is lightly baffled. Again, a perfect compromise(weight and sound) for my use.

N

fstockcarrera

The Euro premuffler is straight through with a resonance chamber.

A straight through cat by pass is louder with 3rwhp+ and -3rwtq over the premuffler. If any of you guys are lucky enough to have the early 1990 ECU turn the motronic switch position 2 as these engines run very lean @ 6000 rpm's this will give 6.3% more fuel and 11rwhp. The 964 engines rebuilt to the Porsche spec of 11.3:1 compression not as delivered 10.4:1 and will benefit best by a dyno tuned AFR optimized Chip to maximize WRHP. These cars have tremendous potential HP and Track performance.
Bob

agentpennypacker

Bob - I have the early ECU. Where is this "switch" - is it physically on the board?


You can send me an email at chris.picklo@cerner.com if that is more appropriate.