max injector duty cycle or ecu issue? - solved

[antus]

Ive been tracking an issue of my car cutting out under load. Ive been assuming it was an issue with spark, and ive tried quite a lot of things on the spark side to diagnose it. It was suggested to me today by another gemini twin cam efi owner (blackcoupe) that it could be the injectors maxing out. I assumed that my camira 2L injectors would be able to keep up on an isuzu 2L engine, and hadnt really considered this possibility. After charting the injector duty cycle against RPM and TPS, it looks like its dropping out at about 80%, which I recall in generally about the limit. Can anyone confirm that this looks like an injector size issue? I hope that this is the case as it will be good to know what the problem is and be able to fix it! I also hope someone can learn from this and hopefully consider injector size far sooner than I did.

Can anyone suggest any common junk yard injectors that would be a straight swap for camira injectors but with a higher flow rate?

[delcowizzid]

100% is where they will stop adding fuel 80% is the safe maximum to leave some headroom funny the duty cycle drops for no reason while at WOT its looking like the tune is set to lean out or its hitting a max pulsewidth setting in the tune you should email me that bin again i think i lost it in my PC crash a while back

[VL400]

I think you need to get some 30Hz logging working! The injector duty cycle dropping may be the RPM signal dropping more than what the monitor plot shows causing it look at a different VE point. It may be a noisy ref pulse signal or ignition module issue. Get an almost identical issue on my mates car with camira module, have not tried replacing the module yet as its a very random thing and can drive through it.

[delcowizzid]

i didnt even see the rpm dip yeah be accelerating so fast you missed some supposidly if the module has the reluctor connected backwards does things like that and puts the base timing out as well

[UCMatt]

I too would be looking at ignition. 80% duty is not a problem. Above this level you may start to lean out, but it won't cut out.
An overly RICH mixture can cause what you are seeing. The spark drowns, and it almost feels like you have hit the rev limiter.

If you are after bigger injectors on the cheap, 2.6L magna injectors are a drop in replacement, and are the same as HSV used on some of the 5.7l stroker motors.

[Holden202T]

is there any chance the injector calculations are wrong and its actually hitting 100% duty cycle but its just that the aldl shows it as 80% ?

[antus]

I dont think the injectors would be hitting max, as the problem is worse in hot temperature. when the ambient temp is lower outside the car its ok for longer, and with the colder air density it should be using more fuel. It doesnt always do it, either, even when hot. I'll get the OSE12P beta on there soon and log it at 30hz and see if that shows anything up. Im thinking VL400 is on to something with a quick RPM glitch that makes it pick the wrong cell, and deliver the wrong fuel. I do have 1 log where the RPM spikes to the max on the table, so maybe that one hit the lucky moment where the rpm did glitch.

[antus]

whatever this was caused by (still hope to figure that out), OSE12P handles it a lot better - it does not happen after a code change

[antus]

Solved - it was the ECU itself! New '808 running SP3 launching time and time again in the heat has been fine. But back to OSE testing

[delcowizzid]

nice one mate good to hear shes fixed how longs it been now LOL