Author Topic: Injector settings - divider/# of injectors, vs Reqfuel, etc.  (Read 120 times)

Offline v2rocket

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Injector settings - divider/# of injectors, vs Reqfuel, etc.
« on: October 26, 2020, 09:42:04 pm »
Hello,

I bought a PnP VEMS kit for my SOHC Porsche 944 n/a 5 years ago.
It is made to plug into the 944 engine harness with some wiring adapters.

With this setup there is no cam sync, only primary and secondary VR crank triggers.
Engine runs a coil and traditional distributor on camshaft.
In the Porsche wiring harness the injectors are wired as 2 pairs but a single driver; the engine runs simultaneous/batch injection.

I have been having an issue for several years that I can't quite figure out - the engine idles extremely rich (target 0.97-1.00 lambda, actual WBO2 ~0.75 or so), but it does run smoothly.
I have tried asking other 944 VEMS users for advice along with the tuner who built the ECU but have not sorted it out.

Engine is 2931cc, 4 cylinder, 400cc injectors which Reqfuel equation says should be 11.88ms. I am running E85 fuel (actual ethanol content ~80%) so that should theoretically be as high as 14-15ms. But even taking Reqfuel down to 5ms with engine idling does not really affect the actual lambda reading. Seems to run better with reqfuel 10ms vs calculated 11.88. Injector dead time was set to the injectors being used. At operating temperature total enrichment is 100% but still seeing 0.72-0.78 lambda at idle.

Remember this is LAMBDA not AFR so the numbers are correct whether E85 or gasoline.

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What I want to know is, does the reqfuel value need to change when changing the injector divider or # of injectors under Injector Settings? I can run fine on 1;4 and 2;2 (very rich), but going to 4;1 runs extremely lean (1.3 lambda) and sounds like cylinder(s) are missing, even when wildly increasing the reqfuel to bring lambda closer to 1.00. I tried 2;4, 4;2, without luck. 3;2 got lambda of 1.00 but sounds like cylinders are missing.

I have searched several times on google and on this website and there are no useful definitions to be found for Divider, or how # of injectors in the tune relates to how injectors are wired.


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I will post a config file when I get home today.
« Last Edit: October 26, 2020, 09:54:03 pm by v2rocket »

Offline v2rocket

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Re: Injector settings - divider/# of injectors, vs Reqfuel, etc.
« Reply #1 on: October 27, 2020, 04:32:53 am »
i cant figure out how to add an attachment, how can i post a config?