CAT Bypass Pipe & Aftermarket Muffler Question

wcc · 09-07-2006, 03:14 AM

This really isn't which one I should get, but what the heck happened and have any of you guys run into this?

I have a Schnell Test pipe and a Borla 1in\4out. With the factory CAT on there the PS was a little higher then the DS. Now with the Test pipe installed the PS is way higher.

Should I return it and put the CAT back on?

Return it and try another brand?

Cut the muffler, rotate, and weld it back up?

What are your thoughts, ideas, suggestions?

Oh Haha · 09-07-2006, 03:19 AM

Bill, I don't think it looks much different. I noticed it sat kind of crooked when we removed it but it fit the valance well. Does the flange on the test pipe where it meets the muffler move? You may be able to tilt the muffler just enough.

What about the O2 sensor? Will the car run ok without it?

wcc · 09-07-2006, 03:26 AM

It was crooked, but do you think it was that much? I just don't want to try putting the engine\trans back in and have the PS tips hitting the bumper.

There is a bung for the O2 sensor. I just haven't re-installed it yet. But it's there.

mb911 · mb911's Garage

the schnell stuff is not your well thought out stuff . I have just been contact with the folks in the know and they had nothing good to say about the products.

anyhow I would guess it needs to be rotated(flange on cat bypass)

javadog · 09-07-2006, 04:36 AM

I have to say, I don't like this. I have used Borla mufflers before on other cars (not a 911) and they fit fine. I have a hard time believing this is what they intended the installation to look like. The brackets attached to the muffler and the way the straps are routed don't look like something Borla would do. The ones I have used all mounted in the stock locations with the stock mounting points.

Two questions:

Do you know for sure that this muffler is intended for your car (I assume you're putting this on the '85 911) and not another year/model?

Does the cat bypass pipe duplicate, exactly, the length of the original cat?

If it were mine, I'd start all over. I'd remove the muffler and bypass pipe and install the engine back into the car. Then, I would make a muffler bracket to mount the muffler in the stock location, or modify an original bracket to fit the shape of the Borla muffler. Having done that, I'd have a muffler shop modify the cat bypass pipe to fit the new location of the muffler inlet.

JR

carnutzzz · 09-07-2006, 06:05 AM

Quote:

Originally posted by javadog

Does the cat bypass pipe duplicate, exactly, the length of the original cat?
JR

This is pretty key. I had tip height problems until I discovered that the cat-bypass pipe was in fact about 3/4 inch shorter than the stock cat.

Just lay the cat on some paper, trace inlet/outlet, then lay the bypass on for comparison.

JBO · 09-07-2006, 06:34 AM

It can be made to work. Had the same issue with my GHL, but after loosening all the bolts and some fiddling then retightening I got it almost perfect. The tip was fine, but I didn't like the can being uneven when looking from behind the car.

wcc · 09-07-2006, 07:24 AM

Quote:

Originally posted by javadog
I have to say, I don't like this. I have used Borla mufflers before on other cars (not a 911) and they fit fine. I have a hard time believing this is what they intended the installation to look like. The brackets attached to the muffler and the way the straps are routed don't look like something Borla would do. The ones I have used all mounted in the stock locations with the stock mounting points.

Two questions:

Do you know for sure that this muffler is intended for your car (I assume you're putting this on the '85 911) and not another year/model?

Does the cat bypass pipe duplicate, exactly, the length of the original cat?

If it were mine, I'd start all over. I'd remove the muffler and bypass pipe and install the engine back into the car. Then, I would make a muffler bracket to mount the muffler in the stock location, or modify an original bracket to fit the shape of the Borla muffler. Having done that, I'd have a muffler shop modify the cat bypass pipe to fit the new location of the muffler inlet.

JR

Well the muffler fit fine with the OEM CAT on there. Yes, my '85. It wasn't till I installed this test pipe that it looks off. So I don't believe it is the muffler cause it was fine before. So it must be this pipe.

Good tip on being the same length as the CAT. I'll have to trace it out and see how they compare. I'm tempted on just returning it and picking up something else that matches like it should.

wcc · 09-22-2006, 12:58 PM

I returned the Schnell pipe and bought a GHL Bypass pipe. The fit was WAY better. Check it out:

PS: I also noticed that the Schnell CAT bypass pipe had the O2 bung on the upper pipe instead of after the two pipes came together. Just out of curiosity, how would that have affected the way the O2 sensor worked and would it have made the car run crappy?

Oh Haha · 09-22-2006, 03:17 PM

Looks better. Can't wait to hear her run!!!!

wcc · 09-22-2006, 04:29 PM

I know, me too! I can't wait to get this thing back together. The longer this thing is out the more it costs me. Budget? What's that? I'm so over budget on this now it isn't even funny! Oh well, it's a hobby. But this pipe was a lot better fit. After the engine is off that dolly I want to adjust those muffler straps cause one is kinda slipping off now and I couldn't get it to slide between the dolly and the muffler. Tomorrow I'm going to try to polish the tips up some. But other than that I think I'm done until that trans shows up.