WALTSTAR

What year 928s share (or with minimal work, share) exhaust system dimensions?
In other words, what can I bolt into what, without too much trouble (welding, cutting, etc)?
Shes just waiting for spring!

Hilton

It depends..

Depending on geography, engine type, manifolds etc. there are a few different combinationf of exhaust.

Yours looks to be an 80-86 US model, which means it has either got cast iron manifolds feeding a single exhaust pipe from the cats back.. or its stainless manifolds with a dual-exhaust all the way with a connecting pipe for the O2 sensor.

What are you wanting to do? Different (better) noise? Power? Fixing rust issues? etc.

davek9

What year is the car, makes a BIG difference.

James Bailey

Since you have an 84 with the single outlet catalytic convertor 79-84 is all that bolts up to that....however if you fit the later 85> dual outlet Cat...you could run the 85-early 86 dual pipe exhaust which has two pipes side by side (also used on Euro S ) . The 86 1/2 will not fit around the battery box. and 87 > is much different as well.

WALTSTAR

I was interested in freeing up the exhaust without going to a custom setup. there are no rust or noise issues, it just appears that the single exhaust on my 84 compromises the potential of the engine. I scored a full 85 setup as James described and will probably put it under the car in the spring. i wanted to know exactly what you guys told me. thanks, James!

James Bailey

Porsche considered the single pipe system inadequate for the 300 hp S .....

pinballplanet

Assuming all other things being equal, does an 85 exhaust set up adding the dual pipes back of the cat add any horsepower over the stock 84 set up and how much added weight is there going to the dual pipes? Is there a noticeable difference in sound for the two exhaust set ups?

Speedtoys

If you're worried about weight...bought the wrong car.

terry gt

Ok ,
Jim how did you know its a 84?
To the OP check out Borla they have a bolt in system

WALTSTAR

Jim probably checked one of my other posts. I already have a stock dual system coming to me from Canada, but thanks for the heads up! Any thoughts on how to clean out the cats before putting it under the car? I figure to do it before and not worrying about it after.

James Bailey

if by clean out you mean beating out the honeycomb internals that will cause the exhaust to have a very annoying droning sound at certain RPMs .... far better to fit an X pipe which will probably help make more power as well. Also the dust from the cat is I believe toxic as well so use caution.

The Forgotten On

If you literally mean clean them out, soaking them in soapy water can help clean out all of the carbon.

Its relatively well known but can have mixed results in how effective it is depending on how far gone your cats are.

Landseer

Don't be surprised if you encounter a little struggle mating the 85 down pipes to the 84 cost iron headers. There is a bit of dimension difference but it's doable. I have entire 85 system under my 84 USA car.

If you.use 85 headers, also, then you will need to have an exhaust guy wack and lengthen the passenger downpipe a few inches. I plan to make that change to mine this winter.

pinballplanet

I'm not worried about weight, and I am very happy with my car. I am just asking, what's the gain of an '85 exhaust from the cat and back over a stock '84 set up since I haven't seen prior reference to that particular modification among all of the posts about exhaust modifications in this forum.

Steve

WALTSTAR

I actually did mean cleaning them out and not gutting them. I figured "why not"? since I wouldnt want to find out they needed it after installing them. I figured the bolt in wouldnt be painless, thanks for the info, Landseer. What exactly should I be looking forward to?