Re: ECM for 4cyl &Altitude (was 747 & 4cyls)

["Bruce Plecan" <nacelp@bright.net>]

> >Peak and Hold, low resistance injector (usually around 2 ohms)
> >Saturated, higher resistance
> >the TBIs use the P+Hs since they first so much more often
> Just incase you missed the above, Andy, you have here a classic
> Pelicanism. An opaque clause rendered so by substitution of the bona
> fide word "first" with the intended word "fire". :)  Not even a
> spell-checker woulda caught it. [Oh, hi Bruce]. You just have to get
> used to his fingers working that way. Hee hee.

Gimme a wrench anytime.  Typing / spelling / grammar not my strong points
(talk about obvious)

> Seriously, he's referring to the fact that the TBI injectors fire
> (when not used in pairs), once every crank rev; so twice as often as
> PIs. And P&H injectors are able to open/close faster than SATs, hence
> their selection in TBI apps.
> >So x% change in adjustment leaves enough head room for that.
> Bruce, some data here; there appears to be ample headroom with the
> stock injectors, since some of our guys have been adding reprofiled
> cams that improve the high-end HP by about 15-20%, and some are using
> the stock EFI with good results with these cams. Besides, if need be,
> the injectors CAN be upsized. That's the least of our issues really, I
> would think.

> BTW, Andy's being kinda modest intentionally; he's actually a
> journeyman Honda tech with lots of experience (sorry Andy for blowing
> your cover), but of course, step into a new world (GM ECM), and lots
> of things are different, at least on the surface. He's using a
> Soob/Fuji engine in his XA aircraft, like the rest of us, because
> their boxer config allows them to be lighter, even amongst the
> all-alum engines.
> >> What's the lowest K/Pa the sensor/ecm can function properly at?  I was
> >> hoping for a system that I don't need to adjust AFR during flight.

> I might be making things worse here to butt in, but I think Bruce was
> worried about the MAP sensor being able to take the lower pressures at
> altitude. But that would be referring to it's OUTSIDE/ambient
> environment; the sensor itself IS an "absolute" pressure sensor, so as
> long as you don't "break" it by going into outer space with it, and
> causing a leak thru the outside housing, it's going to be the right
> "range" regardless of being up at altitude. The main thing to note
> here is that the MAP sensor is just gonna be operating at a narrower
> range when at altitude. It's not seeing some new/strange environment
> as far as the manifold pressures are concerned, just a narrow range.

Even as robust as GM makes things, I'd still carry one aloft a few times jus
to make sure things are as they should be.  I mean develope a system and
then find out the main sensor dies after 10 hours flight time, would not
make my day.  It probably will be fine, just worth trying thou.

> As far as adjustments are concerned, Andy, are you intending to run
> Mogas exclusively and retain an O2 sensor? I gather from the above you
> are. Sorry for the confusion; previously I was trying to outline the
> "worst case" of long-term forced usage of 100LL. Hence, the
> presumption of no closed-loop, and a manual mixture tweak instead.
> See, even in XA, the options run the gamut. Life is complicated,
> id'nit?

Can get overly so if ya let it
Bruce
>
> HTH,
> Gar
>
>
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