Injector Duty Cycle spike ??

[oztracktuning]

I just noticed that my duty cycle seems to spike at high rpm. Does this indicate anything is not right??

Here is a snapshot of the log. The car has SVO 30 injectors.




One frame earlier the injector pulse width was 80% and 14.954m/s

[joecar]

INJDC is a calculated pid using IBPW and RPM (right click on INJDC pid, More Info)...

IBPW looks flat, RPM looks like smooth ramp up, INJDC up swing (at cursor) does not make sense.

INJDC before gear shift is wobbly, does not match RPM ramp up.
INJDC after gear shift matches RPM ramp up.

Or so it seems to me (I only slept 3 hours last night...)...?

[oztracktuning]

I am wondering if fuel pressure is an issue or if i need to set the offset table to suit the injectors.

It would seem to be more likely that the fuel pump is not up to the task?? If that happened does the pcm quickly compensate for lack of pressure by ramping up pulse width??

[joecar]

PCM does not measure the fuel pressure and/or the flow rate;
PCM uses the IFR table to get flow rate.
Your IBPW is constant at 15.6ms (15.595ms).
For constant IBPW, the INJDC goes up as RPM goes up (the cyclic period decreases, making duty cycle a larger percentage).
INJDC is calculated by Scan Tool.

Regards
Joe

[Blacky]

The IBPW scale is too large to see anything useful, try changing it to range from 0 to 20 - instead of 0 to 500. You will see the IBPW jump up, matching the duty cycle.

Regardless, based on the PLX output, the mixture gets richer without the commanded AFR decreasing. Maybe it's Cat overtemp protection kicking in.
I can't remember if the extra fuel for COT shows up in the commanded AFR or not.

Regards
Paul

[joecar]

The IBPW scale is too large to see anything useful

Ah, I missed that, I just saw flat...

Ha, here's my problem...

...(I only slept 3 hours last night...)...?

[Delco]

The IBPW scale is too large to see anything useful, try changing it to range from 0 to 20 - instead of 0 to 500. You will see the IBPW jump up, matching the duty cycle.

Regardless, based on the PLX output, the mixture gets richer without the commanded AFR decreasing. Maybe it's Cat overtemp protection kicking in.
I can't remember if the extra fuel for COT shows up in the commanded AFR or not.

Regards
Paul

May also just be the VE-s are too high at that point , as the efficiency of the motor falls off the VE's need to also fall.

Change your scaling of the parameters to also reflect the expected min max values .

Also when using a injector such as the 36lb ones there is no right or wrong inj flow table , take the 36lb injector as a example , the SVO ones have a miles different flow charteristic than the Holden Supercharged ones , at 100% duty cycle they both flow the same but at every other % duty cycle the Holden ones flow different to the SVO ones , We can always get good control with the supercharged disc injector at low openings , the SVO pintle injector has problems flowing at low % openings - not really related to this thread but I noticed you asked in another thread.

[oztracktuning]

Thanks Delco
I am not sure if the 6400rpm cell in the VE table represents
1. starting at 6400rpm ending at 6799rpm and needing to cover the whole range or
2. Blending with the 6000 at 6200 and the 6800 cell at 6600?

Which one is it.

I just got another log of the same thing today.
Here are the numbers rather than the pic.

[oztracktuning]

My battery voltage is doing something funny??

[Blacky]

I am not sure if the 6400rpm cell in the VE table represents
1. starting at 6400rpm ending at 6799rpm and needing to cover the whole range or
2. Blending with the 6000 at 6200 and the 6800 cell at 6600?

Which one is it.

Do a search on this forum for "interpolation". That explains how the PCM figures out the values "in between cells".
Regards
Paul