924Board.org

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England

Hi ive got a 1981 924 turbo which has been fully rebuilt and an intercooer of a 944 turbo fitted . But was then put in storage for a few years the engine runs great but makes no boost ive fitteda boost guage and all i get is from -20 to 0 on the guage . I can here the turbo whisling and have a dump valve fitted in the system which operates as it should when the boost should be their .

Any ideas please help ???????????????????

924guy · Posted: Thu Oct 25, 2007 8:47 pm Post subject:

if you can hear the turbo spinning, its working.. seems to me youve got a leak somewhere thats stopping it from building pressure. why does it have a dump valve? the factory waste gate has a built in relief valve, any added dump valve is going to hurt performance if your using the factory waste gate setup imo...and could be the root of your problem.
_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

wow...superb looking 931 !
check for leaks and also check your boost gauge. its a bit weird that the "leak" is causing the gauge to show exactly 0 bar.
_________________
Supercharger and EFI kits
https://www.the924.com

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Did the gauge ever work? Maybe it's plumbed into the wrong spot. . .
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Smoothie · Posted: Fri Oct 26, 2007 2:16 am Post subject:

Good point. With vacuum, but no boost reading, you might find the gauges' line is T'ed in at the wrong side of a check valve. To get useful readings of both vacuum and boost, it would need to be T'ed in on the manifold side of any check valves.
_________________
"..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

flosho · Posted: Fri Oct 26, 2007 4:49 am Post subject:

Can you feel the boost kick in around 3k rpm? If you can feel it boosting, then the gauge is either faulty or tee'd in wrong.

Also.. you should post some pics of the engine bay and more of the car in general.
_________________
[This Space For Rent]

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England

vexed73 · Joined: 05 Oct 2007 Posts: 187 Location: EASTERN, nc.

Love those wheels! do they fit with no modifications?
_________________
1982 PORSCHE 931

Smoothie · Posted: Sat Oct 27, 2007 12:32 am Post subject:

If the gauge and its' hook-up are good, and there really is no boost, a stuck-opened wastegate would be a possibility.
_________________
"..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

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

And why is there a "dump valve" again? Was the waste gate removed?
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

bigredtruck69 · Joined: 18 Oct 2007 Posts: 17 Location: Preston England

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Wastegates rarely fail open unless the spring is broken, which I haven't heard of. Even with it completely open, I'm not convinced that you would get zero boost. I think there would still be enough exhaust pressure to spin up the turbo to make pressure.

What I have heard of (and seen) is a turbo that is so cooked that it isn't spinning at all. The only way to find out is to pull the downpipe and try spinning it with your fingers to see how it feels.

I concur, get rid of the dump valve. It's just killing your fuel mileage and nothing else. The turbo has a recirculating valve built in.
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Smoothie · Posted: Sat Oct 27, 2007 4:15 am Post subject:

The OE 931 turbo has a bypass valve built into its' compressor side which I believe makes a dump valve somewhat redundant.

A torn wastegate diaphragm would leave the wastegate closed all the time and cause the opposite problem of unlimited boost (until the overboost cutoff switch opens to shut off the fuel pumps - at which time you'd be rudely awakened by a sudden decelleration).
Wastegate stuck opened all the time would leave you with no boost.

Six or eight small bolts around its' perimeter hold the wastegate together. To deal with it, you'd normally place it on the ground and kneel in front of it and make the sign of the cross, then loosen the bolts with a wrench in one hand and hold the top down with the other. You may be impressed by the size of the spring when it's sprung, but the level of difficulty will depend on which spring is installed, and I'd rate it as do-able by most able bodied do-it-yourself types.
_________________
"..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

Tigger937 · Posted: Sat Oct 27, 2007 11:18 am Post subject:

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Yeah it was interesting to swap out the .5 BAR spring for the 1.0.

Good thing I'm a bit fat dude.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3