Does anyone know what the “stock” exaust pipe diameters are on the different MY 928's?

Did they change sizes from say 79 through 85, 85 through 86.5 or S4 through GTS?

79 - ? Pipe size
85 - ? Pipe size
86.5 - ? Pipe size
89 - ? Pipe sizes

I did a search and did not find any information on pipe diameters.

I did find quite a few threads on exaust modifications people were doing or had planned.

Any of you Guys/Gals that have done exhaust mods on your 928, how did it turn out?

Did you see the results you where hopping for?


TIA <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Max

 

Max-

I have the Cat Bypass and RMB on my 87 with the original mid mufflers. All of the piping is the original size.

Something to note maybe - the mufflers on the 88 are actually smaller than on the 87. Don't know how this applies - just thought I'd pass it on.

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Max,

Kind of complicated, but not really.

Basically (for US models) the system was a 2 into 1 system until 1985. That is, 2 headers fed into 1 cat, and ran 1 tube all the way back to the rear muffler. I have seen euro cars in a variety of configs on this depending on the presence of a cat.

From 1985+, it was a dual pipe system in a couple of different layouts, but basically 2 pipes all the way back, terminating in a single rear muffler.

Now to the meat of the matter.

-Pre 85 US - single 3" from the single cat all the way back to the rear muffler.
-Post 85 US - dual 2" pipes from the headers, through the either (early) 2 pipe in, 2 pipe out single cat, or, 2 separate cats (87+). Dual 2" pipes all the way back to the single rear muffler.

Routing shifted several times throughout the life of the car, to improve performance, and to meet ever more stringent EU drive-by nooise standards.

Those sizes are roughly correct. I spent a lot of time messing with different exhausts on my car, and sometimes the pipes were 2 1/8" ID, sometimes OD. But, roughly speaking, it was either 2" or 3" from the factory.

HTH,

Greg

 

Great info. Guys,thanks!

Has anyone done before and after Dyno run to see if they made any real progress?

At what RPM level did the improvment occured?

Thanks again for the input <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Max

 

Max check <a href="http://members.prestige.net/jpirtle/keepers/index.htm#exhaust" target="_blank">John Pirtle</a> web page. Some good reading about exhausts+dyno. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />