firemn131

Hey gang.
I just picked up a set of cat bypass pipes for my 87 928 s4 auto.
they are in the shape of an "H".
here is the issue..
the cross over in the H is just a spacer tube..there are no openings. so basically they are straight thru pipes..there is a dummy O2 sensor hole in the cross-member...will the car run ok with no inputs from the O2 sensor?
Has anyone ever used these before?

cfc928gt

The crossover should be open, what makes you think it's not?

firemn131

I put air in it and capped the ends..nothing came out the center port...Apparently the H and O2 port were put in to fool an emissions inspector...If I bolt it up< can I just put the O2 sensor on one side or the other?

928 at last

Where did you source those?

cfc928gt

That's really pathetic. Yeah, put it in either side. You might want to consider an X-pipe, it will give you lots more power. IIRC, those H pipes were only 2" tubes which are smaller than the stock pipes.

firemn131

It was given to me...I am not too worried about more power,,,I want it to see if i like the sound better, and i want to do away with the cats...I have heard a few stories about the cats getting so hot that fires have started. I will dive into the car in the next few months and am planning my maintenance..

928 at last

Seriously, Give 'em back and go for a proper "X" pipe setup. You can get high flow cats too. The fires are usually the result of "Operator Error" thinking there's a limp home mode. Read up on here about it. Search is your friend.

Mrmerlin

those pipes may not fit your it looks like an extension was welded on to the right pipe a test fit would be good B4 you remove your old cats,
The 02 needs to read the ex gas, if not your may not run well

Imo000

I have the same looking one (less the extension) but the corssover pipe is open to the exhaust. However the air tube was a dead end.

hacker-pschorr

+1

Also, take a look at the FAQ at the top of the forum, a lot of good knowledge in there:

https://rennlist.com/forums/928-foru...questions.html

Leon Speed

Those look like somebody's home brew. Get a real x-pipe (or take this one apart, cut some holes and weld it together).

Imo000

That's not a home brew. At least one of the big 3 used to sell them before the X hit the market. If it was home made, the balaning pipe wouldn't be oval and it's unlikely it would be all mandrel bent pipes.

James Bailey

The extention was probably to fit it to the 85-86 stainless manifolds when fitted to the 16v heads....since it moves the three hole flanges one side forward and the other side back. So I doubt it will fit your car as it is.