O2 sensor meter

[Howard Chu]

> From: "Bruce" <nacelp at bright.net>

> The ecm doesn't home in on Stoich.
> It averages it.  It purposely toggles rich and lean of it to keep the
> converter happy.
> Bruce

Yes, I realize this. But most meters I've seen give you the real time
sensor reading, which is always oscillating back and forth as the ECU
does its job. This is really only telling you whether or not things
have gotten extreme, like pegging at full rich while you're at WOT.
Since it is in fact the average that the ECU cares about, it would make
sense to display the average, not just the instantaneous reading. Also, it
would be more informative in the case of errors: if the average really isn't
staying near stoich, that might indicate a problem somewhere, but if all you
see is the oscillation, you have no idea what the average is.

> From: "Howard Chu" <hyc at highlandsun.com>
> Subject: O2 sensor meter
> > Y'know, what would really make something like this useful is a dual
> > meter, where the second meter is a delayed/moving average. Then you
> > could actually see how well the ECU is doing at homing in on stoich.
> > How about a buffer from the O2 sensor that charges a small cap, with
> > a short time constant to feed the second LED bank?
> >   -- Howard Chu

> From: "Bruce" <nacelp at bright.net>
> Subject: Re: ignition coils?
>
> While not DIY, FAST (formerly Speedpro), has what's called eDIST.
> Uses the LS1 coil near plug coils.  Just add a cam synch., signal to your
> system, then wire as necessary.   Not a ccheap answer, but still
> an answer,
> where all the details are worked out.

Sounds interesting, I can't seem to find any info on it though.
Has it actually been released yet?

> MAFs are a whole lot more complicated then folks seem to admit.  For the
> time effort energy, why not just go MAP?.
> It also might be easier to swap ecms to something else entirely,
> rather then
> poor so many hours into what you have.
> Bruce

MAP sounds good, yes. I would still use a MAF in the tuning stage to get
the VE curve correct, and hope that the VE doesn't change too much when the
MAF is removed. As for a swap, I haven't seen an aftermarket system that I
like at a price I want to pay. I've looked into ECMs from other Mazda
models/years, but there are still compatibility issues. E.g., the '97
Millenia uses the same engine, with a MAF instead of VAF. This might be a
way to go, but the Millenia's evaporative fuel monitoring system is
different from the '97 MX6/626/Probe. The '98+ 626 is a possibility, it also
uses a MAF, and also uses distributorless ignition. But that means even more
harness/sensor changes... I've got the '97 OBDII manuals, a '99 626 service
manual, various other stuff I've picked up to investigate these swaps, but
none of it looks very practical. It would be easiest just to rewrite the VAF
input code of my existing ECM to work with MAF directly - that mainly
amounts to deleting code, after all.

I've been wondering - why is a speed-density system so sensitive to the
system layout? If you're measuring the pressure inside the manifold, aren't
you dealing with a constant volume at that point? Why should it matter what
breathing changes you've made upstream of the MAP sensor?
  -- Howard

PS: Thanks for your replies. For a while there I thought this was the
Aerocharger fantasy list...

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