[Gmecm] Injector sense

[terry]

Rob,
   From my notes you should have 2.5 to 4.0 volts on
pin 56 for 4 cyl. app. The way you have it is set for
a v8 hence the every 4 drps.
Terry
--- Rob Handley <Robin at FuryWorld.fsnet.co.uk> wrote:

> > Yes,  just leave them open for saturated
> injectors.
> 
> Many thanks.
> 
> > And yes,  the 727 and 749 schematics are the same,
>  the 727 doesn't have 
> > the 2nd injector installed I believe.
> 
> Thanks. I've read that the 730 only has one; so, as
> the 727 and 730 are 
> reputed to be identical inside, I guess this means
> the 727 only has one as 
> well. But 2 sets of pins are used to 'spread the
> load'.
> 
> > 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?
> 
> Thanks Bill,
> 
> Rob
> 
> ----- Original Message ----- 
> From: "Bill Shaw" <b.shaw at comcast.net>
> To: <gmecm at diy-efi.org>
> Sent: 03 September 2007 02:35
> Subject: Re: [Gmecm] Injector sense
> 
> 
> > Yes,  just leave them open for saturated
> injectors.  And yes,  the 727 and 
> > 749 schematics are the same,  the 727 doesn't have
> the 2nd injector 
> > installed I believe.  And yes,  they're all fired
> at once in batch mode, 
> > once per crank revolution,  plus the asynchronous
> pulses.
> > hth,
> >
> > Bill
> >
> >
> > Rob Handley wrote:
> >> Sorry to bring up old stuff, but I've been
> trawling through my personal 
> >> archives and doing Google searches for hours and
> haven't found a 
> >> definitive answer.
> >>
> >> I wanted to be sure what to do with the injector
> sense lines on my '727, 
> >> when connecting 4 high impedance (saturated)
> injectors in parallel.
> >>
> >> The Corvette wiring diagrams on the diy-efi site
> just show injectors 
> >> connected in parallel, and have the 2 injector
> sense pins (that are shown 
> >> on the quadplugecm cross-reference) listed as
> 'not used'. From this I 
> >> deduce that I don't have to worry about the
> injector sense lines. I'd be 
> >> grateful if somebody could confirm.
> >>
> >> Robin 
> 
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