Fuel Injector Timing

[L31Sleeper]

I thought it might be something useful to mess with, now that I have a little
more information I think I'll leave it alone.

Thanx
-Justin

[relentless addiction]

thank you for this useful info, e38 will be my builds pcm! much appreciated

Talking E38.....

{B1205} Injector timing vs. ECT
{B1206} Injector timing vs. RPM

And I believe that the timing in in degrees from TDC on the firing stroke.


As joecar says, the required injector pulse width will be longer than the inlet valve is open for and altering the timing will mess with fuel dynamics.

[joecar]

For example:

at 6000 rpm (100 rev/s), 1 complete cycle (2 revolutions 4 strokes) is 720° and takes 20.0 ms;

if the injector duty cycle was 80%, then the injector on time would be 16.0 ms (i.e. 80/100 * 20 ms);

if the cam's intake lobe had 240° duration, then the intake valve would be open for 6.67 ms (i.e. 240°/720° * 20 ms).

[Redline Motorsports]

I have had good luck by reducing the degrees by 20 on decent size cammed engines.. Much better idle stability and startup. Overlap can pull fuel and not use it so this seems to offset that effect.

[relentless addiction]

For example:

at 6000 rpm (100 rev/s), 1 complete cycle (2 revolutions 4 strokes) is 720° and takes 20.0 ms;

if the injector duty cycle was 80%, then the injector on time would be 16.0 ms (i.e. 80/100 * 20 ms);

if the cam's intake lobe had 240° duration, then the intake valve would be open for 6.67 ms (i.e. 240°/720° * 20 ms).

we need vvt or direct injection