924Board.org

[bass gt]

Guy's,

Do any of you have any real world knowledge of the benefits or pitfalls of a performance exhaust on the 931. We all know what a difference they make to the usual rice rockets, but is there much to be had on out motors. FYI, my car will be a race/track only car, so emmissions are not an issue, but noise is, as many tracks here in the UK are putting noise limits of 98-101db in effect. Not too worried about particular makes, as i live very close to one of the county's best exhaust fabricators, it's just what impact they have on the car.
PS. Im talking from the turbo back, not the manifolds/headers

Many Thanks,

Steve

[924guy]

Vince has a super trap set up on his 931, so hteres at least one of us on here with an after market 931 exhaust system, hopefully hell find this post and give his opinion..

ive considerered it as well, ive got the whole exhaust out now anyhow..but until it goes bad, im not going to mess with it.. it looks like a custom "Y" pipe will have to be made up if the cat is going to be elliminated..the rest should be fairly straight forward...
_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

[Raceboy]

In turbocharged cars theres one rule of thumb (according to C. Bell) in designing exaust systems: to keep the speed of the exaust gases as low as possible. It means straight mufflers with reasonable diameter of tubes. My exaust is stock to the place where WG joins, after that it's 3" to the end, final muffler is straight no-name performance one, it's extracting-type: inlet is 3", outlet is 4".
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[Lizard]

the biggest boost you can do on a cat equiped 931 is gut the cat, or have it removed, and then run straight 3" all the way back, the less restriction in the exhaust the better.
_________________
3 928s,

[Vince Ponz]

It is a little loud but nice. No cat with Supertrapp and no plates on the end.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

[epsylon]

I am running a 951 performance cat-back on my 931 and I think I noticed a slight change in the spool up of the turbo. Seemed to start to spool up at a lower RPM. The exhaust is somewhat louder, stainess steel, and when I got it I was able to roll a tennis ball from one end out to the other.
_________________
'82 931
'78 928
Howell Henderson
South Padre Island

[Vince Ponz]

Search Warlock mufflers they have the standard S shape inside but if you want to make it a straight pipe remove and plate and you have one. If you don't replace the plate and it is a standard muffler.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

[bass gt]

thanks for the thoughts guy's,

Being in the UK, i have spoken to a well known exhaust fabricator, Hayward and Scott. they tell me they can make a turbo back system in 3" pipe, with single back box.
They optimistically reckon on an improvement of 25-30 BHP, which i find a bit hard to swallow!! What i really want is a mild improvement in HP, through better breathing, but a quicker spool up, which can manifest itself as seeming to have more power. I also want to get rid of the restrictive area under the drive shaft area, where it apears the pipe has been flattened to prevent grounding. We shall see!!
other than that, i should beposting pics of the I/C and it's installation, which many of you may find very interesting. it's a modded 951 unit installed at low level in front of the rad.

Regards,

Steve

[u63af]

That will be seriously loud with one silencer. Mine is just the standard system with a magnex backbox and it is loud. I have just bought a 14 ton pipe bender that bends up to 3" pipe so i was going to fabricate an exhaust that is three inch from the turbo back with a small central silencer and a backbox. How much was it going to cost? I live in the uk aswell. Where do you buy your parts from?

[bass gt]

The current pipe is the factory item with the centre box removed. noise is not an issue. Surely a new pipe wont be too different??
I should have added that H&S would fit a 3" from the turbo with a 2.5" rear section.
u63af, what parts are you refering to?

[u63af]

Sorry, i was meaning do you know anywhere in the uk that sells parts at a reasonable price. I need a new universal joint and it is £185 from eurocarparts.

Will having a 2.5 back section not restrict the flow? Can they make a 3" from turbo right the way to the back. Thats what i was wanting to make with a small 3" bore jetex universal silencer in the middle and a universal backbox. Will make exhaust after i do the front mount intercooler in the summer. Using my pipe bender to bend stainless steel pipes for the front mount intercooler.

[bass gt]

Ok,

have you tried Berlyn services? They seem to have loads of parts. however, as these cars get older, the parts prices won't go down!!
Good luck with the I/c job. With a bit of luck, in 2-3 weeks, i will post my pics.

[u63af]

Will be good to see the pics. Will try them for parts. Thanks

[-nick]

"...when I got it I was able to roll a tennis ball from one end out to the other."

I've got to act like a kid for a minute- that's awesome!

nick