crossover pipe? cat-bypass?
 

I wanted to know the difference between the cat-bypass pipe and the cross over pipe, I know what the cat-bypass pipe is, but where and what does the cross over do? Also I have a 911 SC 3.0 any suggestions, mainly for street use. Thanks

cat by pass
 

I went with the cat by pass and felt a noticeable difference. Cheapest ponies I ever bought.

The cross-over pipe, if I'm understanding you correctly, is the pipe that carries exhuast gas from the right side heat exchanger over to the cat or pre-muffler (or by pass pipe). If your car is stock, you have one.

agree with zumwoll, you want a cat bypass and a sport muffler, but even those two haven't satisfied me, I am adding SSIs to the mix so I'll need a 2-inlet muffler and will be selling my cat bypass and Dansk sport 1-in-1-out muffler

I installed the by pass pipe, still have stock heat exchangers, and it made my 78 'SC run much better and cooler.
Best investement you can make.

Bob

I installed a Fabspeed euro pre-muffler in place of the catalytic converter and have been very happy with the result. I have stock exhaust otherwise. There is now much less heat coming from the left rear fender opening and the exhaust note is better and at a lower pitch than before.

David

'89 3.2L coupe

How about sound? Anyone experience cat by pass on 87-89 can post some noise comment? How much lounder?

Cat bypass sound is lower in note but not really any louder to my ears. I trade my cat out after the smog test every year. Without it my 911 passes every test but one here in Houston and that is why it goes back on for the day. Louder is cutting a second outlet in the stock muffler. Way louder.

My car has a borla exhaust with 4 outlet, actually 2 dual. It is loud enough for me, actually a little too loud for my taste. I wouldn't want it any louder, lower is fine. I wonder if I swap in a cat by-pass, or hollow up an old cat, would it be much louder or just lower.

The cat weighed 20+ lbs., that's more than the stock muffler weighs in my 88. The straight thru test pipe let the engine run cooler, improved throttle response and slightly deepened the exhaust tone. Last week put on a modified/gutted stock (one in one out) muffler. This helped the throttle response even more and sounds pretty mellow until 4500 rpm and then takes on a more open sound up to redline. I think its running leaner now and will install a custom chip to max and match fuel and timing maps and improve power. I also drilled my airbox and use a K&N filter. None of these changes cost too much and seem to help the engine breath and don't effect reliability. I'm glad emission rules are not as stringent here as someplace like Ca.

Get it done by Nov. and bring it with you to the Dragon run, and I'll buy it from you. I'm going to do what you are going to undo. :)