Confusion in regards to fuel injecting timing

Hello experts,

im have some trouble getting my head around the fuel injection timing aspect.

the way im tuning this parameter is after my VE is dialed, i would then adjust the angle till i get the richest lambda at different RPMs (should i target MAP as well?)

Correct me if I'm wrong, in terms of MoTeC's injection angles, I assume 0 = TDC compression stroke, 180= TDC intake stroke, 360= TDC exhaust stroke, 540= TDC on power stroke.

Now, when choosing an end of injection timing angle of let's say 400 degrees BTDC, we are limiting our fuel injection to just before the intake valve opening

and as we increase the rpm this end of injection timing is further limited to lets say 450-500 BTDC up to the point where no effect is seen on Lambda (given high injector DC).

Now would it be right to assume that assigning a lower injection timing angle of lets say 200 degrees BTDC would extend injection period to include the period where intake valves are open? ( i saw one mention in MoTeCs help files where it would affect the injector differential pressure which makes perfecrt sense)

would appreciate someone's guidance on this matter.

Thanks!

180 and 540 degrees will be the bottom of the piston travel, and you have those two mixed up.

180 deg = BDC of the Power/Combustion stroke, 540 deg = BDC of the Intake stroke.

So when the End-of-Injection is 360 - 540 you are completing injection while the intake valve(s) are open. At 400 degree end-of-injection, you will have all the fuel in the inlet tract just in time for maximum airflow and usually best mixing. Injector location relative to the valve and the air speed of the inlet will determine what the ideal end-of-injection timing should be.

Your technique of measuring the mixture (looking for a rich mixture) is a valid way to determine if more of the injected fuel is being used, so the engine is more efficient.

Thanks for pointing that out David,

So, within MoTeC, the confusion to me is that injection timings seem to be measured BTDC, which, if I'm not mistaken, would have the intake valves open from 180-360 BTDC?

add to that the fuel injection timing limit of 130-180 degree BTDC which supposedly would lie in the compression stroke?

your answer makes perfect sense to me David i just want to know if that is the way it is interpreted in MoTeC m1, as its quite confusing

Yeah, double check the use of ATDC and BTDC on the values, MoTeC allows you to work either way, and will convert values from one to the other by changing the units. My description is how I think of it, and what seems to match up with my own experiments on the dyno.