Engine starts and runs good and smooth. Aside from getting the BAC to play nice.
Sometimes I get a preignition right at the transition from cranking to running. Like the timing is too advanced.

Im confident the timing is zeroed, and the trigger filtering doesn't seem to have much effect since i presumed it could be noise causing false triggering.

Im an EMS noob and might be way off on something obvious.

 

What kind of crank angle sensor are you running?

Hall Effect, or VR?

Make sure your trigger edge is set correctly

A VR sensor that is wired backwards can also weird the timing out.

 

Stock FC CAS. Sorry I need to setup a Sig with my setup.I keep leaving pertaining info out.

I think it runs too well to have an incorrect trigger wiring? But I dunno for sure.

Cranking rpm setting maybe?

 

OK, I believe you need to have that set to falling edge.

as far as the wiring. It might not be so obvious that it is wired backwards. It would cause the timing to shift slightly, but most noticeably it would float around. this may be worst at the lowest RPM, like cranking.

 

cranking rpm setpoint is where the ecu will kick into sequential injection and ignition
if it sounds like timing is too advanced just as the engine transitions from cranking to running then you should look at the trailing timing settings as this is about when they are enabled

you should have the split around 15 degrees during cranking

the other issue arises with certain brands of coil which have a self protection feature that will discharge them before they overheat and fail
it is entirely possible with these coils that the trailings are cooking off during cranking
as they may have exceeded a safe dwell period whilst the engine was denying them a chance to trigger during cranking
( for similar reasons you should never run that type of coil on duty dwell settings )

dropping the cranking threshold setpoint may actually help in this scenario ( as will changing coils to an accepted LS type that will not auto discharge )

 

If voltage dropped too low while cranking, might the coils fire?

The battery is rear mounted, with power run to a terminal post on the firewall. Then everything is divided from there as if it were a battery. Everything is of adequate gauge...

 

What he is talking about is some coils will self discharge above a certain dwell time/duty cycle.

It has been noted to cause real issues with detonation. The issue usually occurs at higher RPM when people set the mS dwell too high, it causes the duty cycle to exceed the point when they will self discharge. This can cause the the spark to happen several degrees too early with disastrous results.

I guess if your PFC settings were for a certain number of degrees of engine rotation, you could run into a problem while cranking

The only type of coil that I'm aware of that has this issue is one of the varieties of GM LS truck coils. You can find more info on the web.

 

Thanks guys, I will take this all into account to diagnose this hiccup.

 

Thank you. The 15 deg split seems to have solved it.

 

i was getting this same problem, fixed when i increased trigger threshold voltage