123quattro

You might want to think about running a little bit bigger tailpipe. I have 3" inlets (due to headers so this part need not apply) merging into a Y with a 2.5" venturi in it and then back up to 3" all way out the back. 2.5" would probably be ok, but fitting 3" is easy.

GlenL

I was thinking a change in exhaust scavenging until I saw the A/F data. Somethings is going on. The A/F should be nearly the same and that tail divergence is really odd.

hopwood

Well guys I will dyno again after I get the new exhaust next week !!

My exhaust guy is adamant that I do not need 3" with power of less than 350hp. He says 2" on the Y-pipe and 3" for the system after the Y-pipe will be fine.

Have trawled RL and read everything on the topic. Any other comments welcome.

Joel

AO

I'm in the process of building my exhaust too, so I'm interested in what you find. Hope to have the car running again in a couple weeks (need to re-install the oil cooler and re-build my breather setup).

Cheburator

And you kept quiet about it!!!

Once I get the red ****ter back on the road in the next 6mths it will be an interesting match - a 1984 928 Euro S2 with 120k miles on the clock vs. a cherished Frankenstein of a 1980 928

mark kibort

sorry, he is an "xxxx". going from stock 2.5" piping to 3.5" piping got 10hp with no other changes. thats with 190hp to 200rwhp.