EPROM tuning head start

[NickG]

> Date: Mon, 7 Aug 2000 23:54:40 EDT
> From: WEG1192 at aol.com
> Subject: Re: EPROM tuning head start
>
> Ok, so what you are saying is that a perfect tune depends on having
perfect
> weather.

No, I'm saying that a consistent tune depends on all parts of the map being
tuned during similar conditions. Otherwise, the ECM will try to richen some
parts of the map, and lean out others, because the values were tuned under
different conditions. It can drive you nuts if you don't realize this.

> And that at any other time the tune is off and the BLM is depended
> on to keep the motor running at stoich? Also, earlier I saw that the ESC
> should not be used as a tuning aid but that is exactly what happens if you
> use knock retard as an indicator that the timing is advanced a little too
> far. Since the ESC module is what tells the ECM that knock is occurring,
you
> are using it as a tuning aid.

The ideal spark timing is not always just before detonation. Every engine
varies.

> Another thing, I saw recently where it was recommended to use just a DVM
and
> nothing else to tune with. Without a scanner or Diacom, how will you know
the
> BLM, the knock counts, etc.?

Using just a DVM is a GREAT way of doing your first chip. You'll learn a lot
with that method. Turn off closed loop/adaptation, then tune the maps to get
450mv from the O2 sensor at all PT map locations. Note, you'll NEVER get the
O2 to read 450mv; it'll either be above or below it. If changing the map
value by one digit makes the O2 reading go from below to above 450mv (or
vice-versa), rest assured that the tuning at that point is more than close
enough. Heck, 5% off is close enough. This is exactly how I tuned my
turbocharged M3.

> I guess I'm just either too ignorant of what's
> really going on or my idea of a good tune and yours is relative.

You just have to learn and understand exactly how the ECM works. Once that
is done, tuning should be a breeze.

> acceleration. If you define a perfect tune by the summer temperature
outside,
> then during the winter, the engine is not going to be in perfect tune.

Wrong. That's one of the purposes of the BLM and integrator. To adjust to
varying conditions and engine wear. No chip, ever, will keep 128BLM during
all different types of weather. It's impossible. (if it does, then it has O2
feedback disabled ;)

Nick


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