Trigger calibration for distributed spark system (and sequential injection)

[MGV101]

On an distributor based ignition system, cylinder fired is dictated by the distributor correct? So even when the ECU think it is firing cylinder number 1, if the trigger offset is wrong by multiples of 180 degrees (for a 4 cylinder engine) it could actually be firing cylinder 2, 3 or 4. Since the firing intervals are evenly spaced out, the ignition timing would still be correct and a timing light won't be able to tell you that the ECU got the cylinders wrong.

Although ignition timing will not be an issue but wouldn't this affect sequential injection causing injection timing to be wrong by 180/360/540 degrees? I guess to confirm whether the cylinder assignment is correct we could change the trigger offset by increments of 180 degrees while looking at the AFR. The offset with the richest AFR should be the one with the correct offset?

I don't see this documented anywhere in the ECU Online Manual and searching online also yielded nothing so I just wanted to confirm my logic is correct before changing the offset by 180 degrees while the engine is running. (This would definitely be dangerous on a direct spark system)

Seems like this would also apply to a wasted spark system too?

[Vaughan]

yes wasted spark systems can run 360 out and single distributer systems can run any multiple of 720/num cylinders out of sync.

If you visually inspect the orientation of the trigger disc/discs while the engine is sitting at tdc number one it should be possible to determine which of the 4 possible values is correct for your setup. (for missing tooth triggers the offset is from the gap, for multi tooth it is from the sync point).

[Adamw]

Connect timing light to #1 lead, turn on individual cyl ign trim to single mode and put 20deg retard on cyl 1, if your timing mark moves your offset is correct.  

[MGV101]

Thank you for the replies Adam and Vaughan.

Using individual cylinder correct to check is indeed a much better way.