* tuners think in term of the "angular position of the end of injection pulse", BTDC (eg. 430 crankdeg BTDC)

** however obviously the start of the injection pulse is scheduled and activated first

** and the length of the injection pulse is much more important (and respected) than the angular position of the end of the pulse. This more significant effect when RPM changes, it's just good to remember.

* while it is referenced from a future fictive event (TDC), it is always actually actuated from a past real event.

** eg. the ECU firmware sees pulses from primary trigger (and secondary trigger, but timing in general is performed from primary trigger, because it would be stupid otherwise - crank is much more precise, cam sloppiness is known.)

** ECU firmware can only time from past input pulses (eg. that happened 70crankdeg before previous TDC), not from future pulses, and never from fictive (TDC, which is "TDC after the trigger" later than the "actual trigger tooth").

* because it is more versatile this way, the tables can be rotated (by 1..2..N events). This is versatile, and intentional, but if the installer choses to rotate (often as convenience if wiring was not aligned to actual sequence start), it might effect the angle (eg. by 1..2..N full events).

** This can be useful: eg. 430..500 deg values (~220..290 deg after prev TDC) can be actuated more precisely (also when RPM is not constant) than lower injangle values

** the display of cyl number is just optical (as set by the tuner, the ECU and VT has no way to verify if it is correct, nor does it care... it will activate the outputs in order, and installer's responsibility to wire to actuators in correct order)

* there might be other restriction depending on configuration (eg. table rotation by multiple events) that can have effect

* injangle matters at idle and short pulsewidth. At high duty it does not matter (and cannot always be timed to align, because the injpulse length is respected above all). At 100% inj duty the injector angle is undefined, has no meaning (but does not matter anyway even at 50% duty).

** fuel goes into the ports regardless of the time of injection. Some charge robbing between cyls is unavoidable; complete symmetry is impossible, and some robs more than donates; primary factor is fluid dynamics; secondary factor is injangle - but at idle, if all is tuned perfectly we've experienced that injangle can contribute to some change in smoothness - if tuned bad - eg. near leanest operation threshold - it can even have significant effect ... but of course not a workaround tool, the primary tune is to fix first )

Investigating injector timing angles

* if being represented correctly in the ECU (and VT)

** if VT help page needs some more notes about it (eg. effect of rotating tables)

Format of any report abstract, for any questioned point of vemslog is:

* RPM: ...

* spark advance: ... crankdeg

* start of injpulse angle is: ... msec after prev triggertooth (or after ign deactivation)

* length of injection pulse: ... msec measured (vs commanded: ... msec)

* end of injpulse angle is: ... msec => E= ... crankdegrees after prev triggertooth,

** E - "TDC after the trigger" = A = ... crankdegree after prev TDC

** B = 720 - A = ... crankdegree before next (future) TDC

** which is N events after/before the expected angular position of "end of injpulse"

** does it match configured table rotation ?

The injection angle table should be BTDC of "cylinder" (ignout related to given injector output, considering any table rotation) "physical" TDC (actually configured "TDC after the trigger" value) on the compression stroke.