ALDL Tuning (Mode $04 commands)

[Paul Blackmore]

To add to what Malcom Robb said about the potential for disaster when using mode
$04....

Just a little story to illustrate the dangers of Mode $04 commands, even the
(software) experts get it wrong.
A few months back, at a trade show in Sydney, we were demonstrating the software
on an HSV GTS rolling on a hub mounted dyno (www.dynopack.co.nz).
In between dyno runs I was showing some customers how to use the mode $04
commands. I changed the air fuel ratio as an example of what you could do with
EFIlive V4. I forgot to unset the very lean AFR that I had used in the demo.

Along comes the next dyno demonstration run, and we're talking a 400+kW LS1 at
WOT and full dyno load for about 15-20 seconds. I thought it sounded "sweet as",
but the mechanics and dyno operators cut the demo short and started looking over
the car for problems. Me, being a software guy had no idea that anything was
wrong, but the tuners could obviously tell that it had leaned out and was
knocking pretty badly. For about half an hour the tuners tried to figure out why
it was running so lean. I was trying to help them figure it out (I still hadn't
realised that I was to blame) by looking back through the logged run when I
noticed that the commanded AFR was constant. It wasn't trying to lean out or
richen up the AFR at any stage during the run. Then it dawned on me, you know
that horrible feeling you get the instant you realise you've screwed something
up? I 'fessed up and restored the AFR settings and, luckily, everything was
fine.

Tips and traps for young players.

Cheers
Paul Blackmore

> Get the Mode 4 stuff wrong, and you risk a big bang. It looks to me
> that spark adjustment is possible +/- 90 degrees from TDC! Quite dangerous
> at 6000 RPM putting out 400 BHP I suspect. Given that there isn't much
> published info on Mode 4, it's going to require people to dis-assemble each
> and every program mask, just to make sure that some twerp at GM hasn't
> changed the order of some of the parameters.

---snip

Cheers,
Malcolm Robb, LC 0112G



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