Now lean operation, was Re: DIY WB update

[Shannen Durphey]

Are you talking about in general, or with the GN also?  I'd expect (actually,
I'd hope) the turbo would recover some of the heat energy made during lean
cruise and be able to reduce pumping losses.

I look at GM lean cruise as an way to take advantage of the times when you don't
need to use more throttle opening.  Lean cruise is an opportunist.  It should
watch for the times when a little less power won't hurt things, sneak in and
reduce pw for a bit, then get the hell out of there before anybody notices.

Along similar lines, you can save gas by throwing the car in nuetral and
coasting.  But there are times when it helps, there are times when the gain is
zero, and there are times when it hurts.  In other words, a guy  needs to know
enough not to try coasting up the Rockies, and he needs to know enough not to
stay in lean mode when the load is too great.

If I had the time, I'd spend lotsa hours looking for lean best power during
cruise and go there with my tuning, to hell with the leanest possible AFR I
could get outta the ecm.  And when the next engine/car/configuration came along,
I'd start all over again from scratch.

Also nice with a WB to watch AFR during acceleration, and to play around with
keeping AE at a minimum safe setting.  Some cars can stand to have the AE set to
a higher enable tps, saves a little more fuel.  Also lotsa gains in training the
driver!  The guys that like to use the gas pedal like a switch use more fuel. 
The poor ecm is bouncing between AE and PE and never spending enough time in
steady state to hit lean cruise.

'Course lean cruise can help more in cars running numerically higher gear
ratios.  Lotsa trades, but lower gearing means being more right when making
power.  Higher gears can be more forgiving during cruise on the highway if
you're on the lean side.  Lotsa, lotsa trades, and there is definitely no
hard-n-fast rule.  But I've seen gains when going a bit leaner at the right
times.  No, not real lean, but a bit lean.

Shannen


Bruce wrote:
> 
> Speaking of lean cruise.
> I can't find any real big gains in going real lean anyway.  Still need to
> burn x amount of fuel to make a given amount of power to actually move the
> car.  Maybe, better results, in a lighter car, but then you give away all
> the road hugging weight.  the instant you have to run more throttle opening
> from the leaner AFR, then your using more fuel anyway due to the greater air
> flow.  While you might run 10% leaner, if you have to use more throttle
> opening you might be using a larger total amount of fuel.
> Just completely the opposite of what pumping loses would dictate.
> Again, theory falls short of real life....
> Bruce
>
----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org