Question about short pulse adder

[John377]

I think I have a grasp on how the fuel injection system works I just had a quick question about the short pulse adder. I understand that the short pulse adder will be added to the pulse width once it drops below the short pulse limit.

My question is the X axis of the table is reference to what? Is it reference to MS below the set pulse limit? So say if the pulse limit is 3.997 and the ecm is asking for 2ms does the 2ms block ad the referenced value to the pulse limit?

I hope this makes sense... How is it calculated?

This is on a 2002 silverado 6.0l p01 ecm

[Matt Vardaman]

Both are in time - milliseconds. My short pulse adder table doesn't add (or subtract) any time until it gets under 2.5ms. The only time I ever get below that is on DFCO. Under deep decel my injector pulse goes to .7 which is the same number as the injector offset at 14.0 volts. When I was running the stock 25.2lb/hr truck injectors it would go to .2 which was the offset for those injectors at running voltage.

[Matt Vardaman]

http://injectordynamics.com/articles...racterization/

Here's a good writeup about injector characterization.

[LSxpwrdZ]

The axis is the cumulative PW prior to the short pulse adder being added. So if the airflow model is requesting 2ms and the voltage offsets are adding 0.70ms then 2.70ms would be looked up on the short pulse adder table. And if that adds another 0.05ms the total MS logged in the scanner (only on Gen3) will show the final total actual pulsewidth as if you stuck a scope on that output.

Now conversely the Gen4 PW PID does not include all of those adders together in the scanner.