924Board.org

[mariusraael]

Hello to you good sir’s!

I have an 924 turbo S2 where the CiS unit recently has been rebuilt in Australia and I have bought a rebuild WUR from a local, but I suspect it might faulty. I have checked for air leaks and found none. My fuel pump is OK. The problem is that when the car is stationary the AFR is jumping up and down from 13-16, when I give full throttle at stationary the AFR reads 12-10. It is always changing. I am a bit reluctant to test drive it since the AFR readings are so inconsistent. Any suggestions to a solution?

Best Regard Marius[/img][/url]

[924-76]

I suggest you test you fuel pressure with a proper CIS tool, as well as testing your injectors for flow pattern and amount. Those test will tell you a lot about the health and performance of your fuel pump, WUR, fuel metering head and injectors.
I'm assuming you are using a wideband O2 sensor and gauge for the AFR readings?
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[mariusraael]

Thank you for the reply!
That is correct: I use an wideband 02 sensor for AFR readings. I have brand new Bosch injectors and I have checked the flow which was good. I have an psi pressure gauge, would that do the job if I place it between the WUR and the CIS unit at the top fuel line?

[924-76]

Awesome on the wideband O2.
I'm sure the info is available on this site somewhere and it is in the Haynes manual on how to test for fuel pressure. There are 2 different pressure to test.
FYI, new injector doesn't mean they are good. There are been many report of faulty new 924 turbo injectors. That being said, if you test them for flow and pattern, then you are good. Flow is about consistency between the 4 of them, again info is in the Haynes manual on test procedure and acceptable flow amount.
Cheers
_________________
1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

[Fifty50Plus]

Dropping a spark here and there will cause CO to change. I run wideband CO (Inovate system) on my race car and can change the mixture on the fly. It takes several seconds for the CO number to stabilize.
IF you can get it on the highway and look at the CO under load (use brake to hold steady RPM for about 5 seconds) that will give you a better idea of whether you have a problem.
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

[mariusraael]

Thanks for the tip! I’ll definitely check spark plugs and wires! What sort of EFI system are you running since you are able to change mixture on the fly?I will take the car for a test drive to see which reading I get with load. Thanks to all your help!

[morghen]

Sounds like a misfire to me. But can also be fuel related.
Check the wires, the plugs themselves and check that the injectors arent leaking or having a severe imbalance between them. An overly rich or lean cylinder can also have this effect.

If you’ll be looking for an EFI system that is bolt-on, plug-in, comes with a decent tune for your car, and looks very very close to the original CIS, have a look on my website.
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Supercharger and EFI kits
https://www.the924.com

[Cedric]

Where and how is the sensor mounted?

try to test drive it without any high boost and see what readings you get and how stable it is. To be sure its no exhaust leaks etc thats affecting the idle results. It should be around 14-15 when you cruise at light load, be very careful to hammer it before you are fully sure that the AFRs are correct. At full load it should be around AFR 11, to lean and it risk getting a whole in a piston, but keep that for later until its all clear that it works.
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1980 924 Turbo
www.instagram.com/garagecedric/

[924RACR]

Yeah, I'd be leaning into the topic of misfires (no pun intended)... the fueling won't likely change so much/so fast with changes on the CIS side, but before I switched to EFI on my cars they would jump around a fair bit with ignition glitching. Now of course they're nice and stable thanks to all the new tech including a modern 4-post ignition coil...

Fifty50Plus isn't running an EFI conversion - yet... He just has an adjustable WUR or such on his CIS, from what I recall.

I think I'm the only one with an EFI'ed H Prod race 924 so far... and the data from that shows that I need a newer/better fuel pressure regulator, as the one I bought (Holley) is crap!! Pressure is jumping around all over the place... switching to AEM for this coming season...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype