[Gmecm] Injector sense

[Rob Handley]

>> And yes,  they're all fired at once in batch mode,  once per crank 
>> revolution,  plus the asynchronous pulses.
>
> This is the bit that worries me. My tests with the oscilloscope in the 
> garage yesterday indicated that the injectors were being fired once every 
> 4 DRPs - because my (4 cyl) engine was idling at about 800 RPM, with ALDL 
> correctly reporting a DRP interval of ~38 ms. The 'scope was showing ~130 
> ms between pulses - which is _roughly_ 4 x 38 (although disturbingly not 
> close enough for my liking!). I would expect to see 2 x ~38 = ~76 ms if 
> they were firing once per crank revolution.
>
> I'm not _100 %_ sure that I'm reading the 'scope right as I haven't used 
> it before and there's no manual (it was thrown out from work), but the 
> same scope showed an idle injector pulse width which agreed with the ALDL 
> BPW plus the ~0.5 ms battery offset.
>
> BTW: My code ($58) is set for 4 cyl, I've set the max async PW to zero, 
> and my MemCal has the leg of the chip at CAL56 desoldered - which I think 
> selects 4 cyl TPI mode. I've read that the number of DRPs between injector 
> pulses differs whether this pin selects TPI mode or TBI mode - but I'm not 
> clear how many DRPs between pulses in TPI, and how many in TBI.
>
> Have I got something wrong?

To answer myself - YES. Just tried a shiny new 'scope and this time I see 
injector pulses at twice the DRP interval. Phew!

And no sign (on the 'scope) of the big spikes that appear on the ALDL, so I 
reckon that must be another ALDL artefact.

Thanks again Bill.

Rob