[Big Dave]

I have an Ott x-pipe installed on my '85 (no cats) and I would like to modify it to include high-flow catalytic converters w/o adding my air pump back. My plan is to cut/shorten the X-pipe downstream from the X section and add the individual cat units between the shortened x-pipe and the stock exhaust, keeping the stock exhaust from there to the back of the car.

Does anyone recall the dimensions of the Ott x-pipe? I want to make sure I get the right diameter size hi-flow cats to fit the shortened x-pipe. I'm also trying to remember whether the down stream exhaust pipes fit inside the x-pipe connection, or if the x-pipe fits inside the down stream exhaust pipes. I don't have pictures (and I'm being lazy about climbing under the car).

[SeanR]

I have an Ott x-pipe installed on my '85 (no cats) and I would like to modify it to include high-flow catalytic converters w/o adding my air pump back. My plan is to cut/shorten the X-pipe downstream from the X section and add the individual cat units between the shortened x-pipe and the stock exhaust, keeping the stock exhaust from there to the back of the car.

Does anyone recall the dimensions of the Ott x-pipe? I want to make sure I get the right diameter size hi-flow cats to fit the shortened x-pipe. I'm also trying to remember whether the down stream exhaust pipes fit inside the x-pipe connection, or if the x-pipe fits inside the down stream exhaust pipes. I don't have pictures (and I'm being lazy about climbing under the car).

Send Roger an e-mail, he will know and may have them in stock.

[Crumpler]

I think I can help with this one.
Ott xpipe is 2.5 inch.
Stock pipe behind was 2.25 on 86.5. Assume all S3 was 2.25, I believe only the route was altered late 86 for true dual exhaust?
I’m 95 percent sure the x pipe fitted over the stock 2.25, but I went 2.5 all the way back.
What you are planning will work fine in regards to putting the hi flow behind the x.
In theory Big Dave, you could hallow cats and slide them over the existing x pipe ends and weld them on. Don’t know what the situation demands.
I had to pass visual inspection only.

[worf]

... and weld them on.

Or:

https://www.jegs.com/p/JEGS/JEGS-Prefor ... 4/10002/-1