LLY Ficm
- Thread starter mplecha
- Start date
And setting that up is a whole other subject. . .
Files should also play back on most SnapOn scanners.
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Files should also play back on most SnapOn scanners.
Sent from my SM-S901U using Tapatalk
@1FastBrick came thru with some new data tonight. Scoped out that crank trigger pin 94, along with Injector #1 [in red] and Injector#3 [in blue] control wires in several different sweep ranges. It shows us the ECM is in total control, using the 8 injector control wires to send the pulse in "us" to the FICM. Where it gets amped up to 48v, and sent to the injectors.
Still no clear idea what they are using the crank signal for besides a safety, but in the shots you can clearly count the wheel pulses after TDC when the Red Injector 1 fires. Blue Injector #3 trace is at end of our firing order. Couple pix I zoomed in on the Inj pulses, so everyone can see that control wire sends exact pulse width one would expect at idle.
So with a little more work, hopefully we can calculate exactly how much LAG there is between control signal to ficm, and injector being fired. And if that value changes with RPM. Sure there is enough real world data out there on where we need to be on start of those pulses. And recall there being timing calc differences for start of injection between LLY and LBZ in tune files.. Guessing that's our lag offset maybe??
Anyways will post up the files so everyone who wants can hack around and maybe come up with the actual timing offset GM used in this setup. They could always possibly play with the timing in the FICM to adjust for lag, but for now, I still say it's a dumb amp box only.
Still no clear idea what they are using the crank signal for besides a safety, but in the shots you can clearly count the wheel pulses after TDC when the Red Injector 1 fires. Blue Injector #3 trace is at end of our firing order. Couple pix I zoomed in on the Inj pulses, so everyone can see that control wire sends exact pulse width one would expect at idle.
So with a little more work, hopefully we can calculate exactly how much LAG there is between control signal to ficm, and injector being fired. And if that value changes with RPM. Sure there is enough real world data out there on where we need to be on start of those pulses. And recall there being timing calc differences for start of injection between LLY and LBZ in tune files.. Guessing that's our lag offset maybe??
Anyways will post up the files so everyone who wants can hack around and maybe come up with the actual timing offset GM used in this setup. They could always possibly play with the timing in the FICM to adjust for lag, but for now, I still say it's a dumb amp box only.
1 More thing to note. Those were taken at Idle.
I couldn't have got the correct data with out Ken's help. So thank you Ken!
I am curious as to what you find on the LB7 FICM.
1 step closer to a solution!!!
I couldn't have got the correct data with out Ken's help. So thank you Ken!
I am curious as to what you find on the LB7 FICM.
1 step closer to a solution!!!
Great working with you too. As I don't own a good shop scope, or a running Duramax. 
Also before I forget, that missing tooth gap doesn't always exactly signify Cyl#1 TDC of the crankshaft position. Someone out there probably knows the exact deg of mechanical offset, if any. Or has an engine apart with front cover off and can verify thru pickup hole. But I just used end of the gap as our TDC ref in logs. Which shows it at idle firing Cyl #1 pilot about 10,000us after TDC if my math is right. So suggest we verify where #1 TDC trigger falls on plots for future reference.
Also before I forget, that missing tooth gap doesn't always exactly signify Cyl#1 TDC of the crankshaft position. Someone out there probably knows the exact deg of mechanical offset, if any. Or has an engine apart with front cover off and can verify thru pickup hole. But I just used end of the gap as our TDC ref in logs. Which shows it at idle firing Cyl #1 pilot about 10,000us after TDC if my math is right. So suggest we verify where #1 TDC trigger falls on plots for future reference.
That's awesome. Good amount of data with just that. Next would be repeat at say 2k rpm or so. Of you could get someone to do a little power braking to add a little load to the engine so we can see those traces open up.
I wonder, like you said Ken, that the crank is just a safety. If it was to keep the FICM from firing the injectors without any engine RPM. Maybe if there was a voltage spike, engine seized up and stopped turning then the FICM would cut fuel even if the ECM was still trying to run the engine
The next test would be to divorce the crank signal timing from the ECM injector control timing and see if the control or injector firing changes if the crank varies any. If it truly isn't used for timing the pulse then we could ditch it for an even dumber FUCM box build
I wonder, like you said Ken, that the crank is just a safety. If it was to keep the FICM from firing the injectors without any engine RPM. Maybe if there was a voltage spike, engine seized up and stopped turning then the FICM would cut fuel even if the ECM was still trying to run the engine
The next test would be to divorce the crank signal timing from the ECM injector control timing and see if the control or injector firing changes if the crank varies any. If it truly isn't used for timing the pulse then we could ditch it for an even dumber FUCM box build
I am in awe right now. You all are some very smart fellows. Glad you are here, and working as a team.
Here for the moral support of the FUCM box
Some would say SMart Fellows while others might say Fart SMellers...
Either way atleast we are being Pro Acitve for the community as a whole. The way Real Hotroding was ment to be!!!
I guess we also Owe James a Thank You as well since he now owns this site where we are able to come together and work as a team even though we are working remotely.
So Thank You James for keeping the best damn Duramax site going!!!
My running LB 7 didn't materialize today. However, I did find enough to build one on the bench.
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Besides a couple questionable LB7 FICMs, found these in my buddies toolbox. Said he thought both had a hard code set, but I'm still gonna wire em up on bench harness and see what they have to say about life. Beer Money!!
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I drink expensive beer... lol
One has a 2010 date code other 2012
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My cat said this one smells weird. Other one has note on bottom, "needs ground fixed"
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