964 C4 Bypass pipe
 

Would a Schnell or Fabspeed bypass pipe create any negative issues/stress
for the engine on 89 964 C4? The car is equipped with stainless sport exhaust, and secondary muffler has also been eliminated.

Do you have a primary to bypass? If so, it will be loud...but fun for an occasional run. To much for a daily driver (or if you have kids and you want them to hear).

Re 964 bypass pipe
 

Sorry that I wasn't more specific, but my thought was in the direction
of cat. bypass with oxygen sensor fitting. Again, I already have stainless
"rear" muffler, and eliminated R.side(main muffler).

It should not have negative effects on the engine. It will likely make the car louder, it might give it more of a fuel smell, and it will probably free up some power.

Oh, and it will probably make the car fail emissions testing. Emissions may or may not be tested where you reside.

The most used method to free up exhaust and add power is as Porsche did with their Cup cars. Cat delete and primary muffler delete. It should give you the best power and sound. If you already have secondary muffler delete and go with a cat delete it will definetly be louder (too loud). Any time you delete your cat it makes your exhaust louder. In my opinion if you still have the secondary muffler, reinstall it and buy a cat delete and primary muffler delete.

I had all three bypasses and played with them for a while. I settled on what Arrow mentioned with the cat bypass, cup bypass and left the secondary and stock tip. Looks stock but sounds better and opens things up as much as you can without causing back pressure problems. Some people like the sound and power of the cat/secondary delete too. I think its personal preference between the two.

fyi here is some decent info

http://forums.pelicanparts.com/porsche-964-993-technical-forum/653985-964-proto-type-exhaust-v-2-0-a.html

Some people like the sound and power of the cat/secondary delete too. I think its personal preference between the two.

I have to agree with Pnine it all comes down to what you like I started with the Cat in place all the time changeing out the pri. muff and putting it back on then taking off the sec. muff.. The J Pipe I have on now is louder the other sounds like a true P Car really nice. But my butt dyno "not calibrated" seems to tell me there is alot more bottom end with the J Pipe A bit more fun to drive now with a chip installed all the way from 1500 makes you go like this :D. Soon time to to put the pri muff back on for a bit.. You can only go so fast on the street here in the states any how so do what makes you feel good and do not worry about the rest.

I have a G-pipe only on my car and I've heard my car next to a car w/ a Cup Bypass and my car was louder, less centered, and more muscle car sounding. The Cup Bypass car had a mellower, more centered tone w/ a bit of raspiness, basically more or a trademark Porsche flat-6 sound.

I have a Fabspeed test pipe along with a single-in/dual-out Mille Miglia muffler. Absolutely love the way it sounds. Good boxer rumble down low, but opens up with a raspy scream at higher revs... no sound like it IMO.

When i deleted my cat for the test pipe, to me, the change in sound was minor. Was definitely expecting a much bigger difference. I've mainly driven classic muscle cars since i've been driving, so louder exhaust is the norm to me. May not be for everyone.

A part of me actually wishes it was a tad bit louder at idle. :D