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

[Garfield Willis <garwillis@msn.com>]

On Tue, 22 Aug 2000 22:58:15 -0400, "Bruce Plecan" <nacelp@bright.net>
wrote:

>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.

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.

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?

HTH,
Gar


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