Bench racing ecms

[Clare Snyder]

Gregory A. Parmer wrote:
> 
> > voltage is close to 12V anyway. As long as a power supply can provide
> > the current you need, might as well use one, instead of that battery.
> > Lot easier, lighter, safer, less smelly; hey, and if you short most of
> > the PC supplies out, they drop regulation, fold up their legs, and play
> > dead till you cycle the power. Much nicer than a real tractor/auto
> > battery, which normally loves to create fires and explosions if you
> > short it real good.
> 
> I've got my '7747 running on the bench (wall actually) and
> if you plug in the real injectors the power supply doesn't
> handle things well (scanner freaks out and more). With dummy
> loads all is well. I'm using the supply but have a BAT for
> more realistic tests.
> 
> Problem I'm having is getting the intended feedback. Surprisingly
> enough to me, PW seems more closely tied to MAP than TPS.
> On a real engine opening the TPS would reduce MAP and thus
> increase PW. On the bench MAP doesn't change (just because
> of TPS) and blipping the TPS generates only an increased
> PW during the blip..similar to an accel pump. Go figger!
> 
> Another issue has been the dreaded O2. I'm wondering
> if it'll be OK to just fool the ECM into thinking
> it's always right...ie, lots of stoich crossings via
> a wave gen of some sort. That's next, but I haven't
> gotten there just yet. I'm open to better ideas.
> 
> > Your idea of an engine simulator, at whatever level, is right smack in
> > the stateOdeArt of electronics. Is that SCARY, or what?
> 
> Even scarier is dat I'm just crazy enough to be trying
> this too!  Albeit not really electronically simulated.
> 
> -greg
MAP or MAF are almost always the primary inputs. TPS is primarily a
reference - Am I at idle, WOT, or somewhere in between. This helps the
ECU determine if MAP or MAF are within range or if something has gone
haywire. In early systems the O2 sensor could only fine tune the system
by a few percent. Apparently in the current systems the O2 sensor has a
greater say. On the early Toyota EFI (L Jet clone) the opening of the
TPS caused an extra injector pulse coming off idle, and lengthened the
pulse at WOT.
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