924Board.org

TBrown · Posted: Wed Nov 25, 2009 9:38 am Post subject: Questions on 931 air fuel mixture

Im trying to set the air fuel mixture because I think Im getting to much gas the manifold is glowing red hot when Im running it at idle and I only go up to 4000 rpm at the most. So I have a question is this the air fuel mixture screw? The book said this is the idle screw.

Or is that the air screw and one of these is the fuel mixture screw?

Or is this 7mm allen the fuel mixture screw?

And heres the engine with the head back in

_________________
Tangerine Dream- 1980 924 Turbo
Silver Surprise- 1979 924 Turbo
1977 International Scout ii
1982 Yamaha Sr185
1978 Kawasaki KZ650
1974 Honda CB360
1973 Honda CB750

Smoothie

That^ is the idle speed setting.

That^ is where the A:F mixture adjustment is located (the upper item that's circled). You'd remove that Phillips head screw, then go in through the hole with a 3mm allen wrench. -But only after eliminating -all- vacuum leaks, and ruling out all other possible causes of your problem. -And note where the setting is now, before changing it. (clockwise = richer, counterclockwise = leaner)(move only in very small increments)

That^ is the fuel pressure regulator (adjustable via shims inside, not by the allen screw).
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Smoothie · Posted: Wed Nov 25, 2009 10:08 am Post subject:

Glowing exhaust manifold can also be due to late ignition timing, or anything that causes fuel to be still burning as it passes through the manifold.
ie- overly rich mix and/or late timing and/or high octane fuel.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

TBrown · Posted: Wed Nov 25, 2009 10:19 am Post subject:

Awsome thank you smoothie. Yeah I think its a combination of all three of those. I think my ignition is too late and im getting to much fuel. When I get it plated Ill have to drive over to the gas station. I dont know what the octane rating is on the gas thats in there right now its had the same gas since Ive got it, dont worry it has stabil in it. What octane rating do you recommend to run these cars 87 or 89?
_________________
Tangerine Dream- 1980 924 Turbo
Silver Surprise- 1979 924 Turbo
1977 International Scout ii
1982 Yamaha Sr185
1978 Kawasaki KZ650
1974 Honda CB360
1973 Honda CB750

Smoothie · Posted: Wed Nov 25, 2009 10:28 am Post subject:

I go with regular 87.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

TBrown · Posted: Sat Nov 28, 2009 8:09 am Post subject:

Does anyone have any experience using a dwell meter to set the fuel mixture like this previous board member did here here?
_________________
Tangerine Dream- 1980 924 Turbo
Silver Surprise- 1979 924 Turbo
1977 International Scout ii
1982 Yamaha Sr185
1978 Kawasaki KZ650
1974 Honda CB360
1973 Honda CB750

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

The rubber boot between the intake tube and the throttle body looks like it could be causing a vacuum leak. May want to check that and any other areas before attempting an A/F mixture changes.

Dennis
_________________
81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

Yes, dwell meter works fine, set to 45. I've also used a duty/frequency meter and set to 50%.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

alexvex · Posted: Sun Dec 06, 2009 3:39 am Post subject:

I always ran 93. I'd recommend it, especially if you leave the boost controller at 10psi.

Also, forgot to add this to my PM...the nozzile for the meth injection is still in the intake if you hadn't noticed. It's the brass fitting with the screw in it. So in case you ever want to add a meth setup it's already tapped for ya

_________________
--Alex--
1992 Porsche 968 (VW 2.5L I5 Turbo swap in the works)
1995 Audi 90 Quattro Sport (4.2L V8 Swap)
2010 Touareg TDI
Past Pcars: 80 931, 87 924S, 87 951

ManicCycle · Joined: 30 Sep 2009 Posts: 97 Location: earth

I thought 10psi is stock boost for a 931.

stevekat · Joined: 19 Jan 2008 Posts: 719 Location: Los Angeles, CA

I believe it is:

6.2psi to 6.8psi U.S 931 (81/82)
9psi to 9.85psi Euro (81/82)
9.7psi to 10.6psi Euro 79/80
10.45psi to 11.3psi Carrera GT with intercooler.
_________________
"Never get out of the boat. Absolutely goddamn right. Unless you are goin' all the way."

Gone to new home: '81 924T, US version, CGT Intercooler, UTCIS-PT, Euro DITC, Greddy Trust MBC, Forged Fuchs Flat Dish 6's, Factory Recaro's.

Smoothie · Posted: Sun Dec 06, 2009 4:16 am Post subject:

TBrown · Posted: Sun Dec 06, 2009 7:27 am Post subject:

Yeah I turned the boost down to 6 psi. I figured thats where you plumbed the methanol injection into because all of the other charge tubes I've seen don't have the brass fitting.

I've read that if you run 93 the gas burns slower and that can cause a red hot exhaust manifold.

The methanol sounds interesting, how did you wire it all up? And where did you put the Hobbs switch?
_________________
Tangerine Dream- 1980 924 Turbo
Silver Surprise- 1979 924 Turbo
1977 International Scout ii
1982 Yamaha Sr185
1978 Kawasaki KZ650
1974 Honda CB360
1973 Honda CB750

tbramich · Joined: 02 Dec 2009 Posts: 25 Location: charlotte nc USA

in your second picture of the fuel distribution assembly i recently found that there are filters under each of the injector feed lines. you might want to make sure they are clean. should not affect your exhaust being red but it could cause the injectors to be way out of sync which might cause other problems