I was browsing the stickies and came across this
Starting routine final answers

And, had some questions.
1) Does cranking mode use EACH signal from the module to inject a cranking pulse? I know there's the table for injection multiplier vs DRP, but I mean - does it use each one or every fourth??

guess I only have one question for now.

If it's different for different applications, please post what you know.

Thanks,
Jeremy

 

I can't find any hard proof but looking at that PW multiplier table in $8D, seems like every DRP "could" be made to inject. Zeroing out the DRP counts where no fuel will be injected.
The table shows a pattern almost of every 4th but may be sequenced like it is to either allow for more crank fuel or to avoid flooding. I've never looked at what the BPW is for cranking that uses this multiplier.

 

Each *pulse* from the module is a DRP. DRP means Distributor Reference Pulse. So what ever the listing shows, in the table is what it is. The tables can be by intervals of 1, 3, 4, from what I recall off the top of my head.

 

Yeah, I knew what the DRP was, which was throwing me, thinking maybe the ecu file was labeled wrong. Typically, a warm engine needs 75-100% of a full load PW for cranking, but the GM calibrations have smaller injections.

But, I'll try to rationalize it for GM - if you fire on each pulse, you are less likely to shoot a full load on an open intake valve (landing on spark plugs and cylinder walls in very liquid form), and are also more likely to start with as little crank fuel as possible, and the normal injections can switch to once per fourth injection mode immediately without having to keep track of when the last crank pulse was. Also when very cold, the PWs typically get HUGE, but if you fire it 4 times as often, they are 1/4th the size, and maybe there's a calculation limitation that might keep the PW's below a certain length.

Thanks, and any other ways to rationalize this method?? Are my rationalizations rational?

 

I don't remember all the quals, but there is a 8 drp to run mode qual (table) in 8D.
L801C is the table and it is loaded near $b771 in the code.
Some of other masks have this as a constant instead of a table.

 

Ok, so that should set the absolute minimum fuel it gets, whether it needs it or not.

Wonder if it goes: crank fuel, sees high enough RPM, then wait until the 4th DRP after that, or does it inject a normal PW directly after the crank fuel and then 4th..... Probably doesn't matter much at all, unless you're going for psuedo perfection (on a batch system).