"Geoff" wrote in message igy.com...
You can do aftermarket SEFI, closed loop with O2 and other cool things
too. Costs money and effort, but it does work, and work well.

What do you mean by "work well"? Is it as good as open loop or measurably
better? Are there noticeable gains in power, torque, startability,
driveability, fuel economy, and/or smoothness? I still maintain that
feedback fuel control exists only to keep a catalyst operating at peak
efficiency. Even closed loop systems go to open loop enriched conditions
under max power situations and/or for the sake of smoothness. I can see
that maybe a closed loop system might be slightly better on gas but if it's
not controlled well then you're playing with fire. Otherwise I think you're
adding complexity for minimal gain. If someone wants to experiment. by all
means go for it - that someone just won't be me.

By work well, I mean improved fuel economy at part throttle for the
ordinary O2 sensors. They don't have a wide enough range to cover
higher throttle settings. It is worth doing. I have such a setup on
a powerful 454 Chevy and the idle quality and fuel economy are very
good considering the high output.

The wideband O2 sensors can go a step further and keep the mixture
"tuned" at WOT also. Haven't tried this yet, but I probably will in
the future. More expensive, I'm waiting for prices to drop.

Yes, you can map your engine open-loop. Obviously, my engine is
mapped open-loop for heavy loads. If you are a knowledgeable engine
tuner you can do a good job. However, it is hard to account for
varying temperatures and air pressures perfectly. Open-loop is
certainly good enough, but it is hard to produce the
perfect-under-all-conditions power and economy that a wideband O2 will
provide.

Lifespeed