WB Instruments

[rr]

(see below)

Brian L Massey wrote:

> On Fri, 13 Jul 2001 17:21:58 -0400 rr <RRauscher at nni.com> writes:
> > Shift point. If I remember correctly this was a roll out to WOT in
> > 2nd gear. I quickly shifted into third and hit it again for a moment.
> Then it
> > was right to 5th.
>
> OK, that explains the puzzle, especially the short throttle off in 3rd,
> after which you punch if for a little longer time, and then go into 5th
> after throttle back in 3rd and the shift into 5th, taking about 2 more
> secs. Now that part makes sense. Looked pretty strange at first.
>
> But I'm still puzzled it seems to take a long time before the fuel cut
> kicks in after the shift from 2nd to 3rd. I'm referring to the events at
> 25:19. It looks like you throttled back after the shift, given the plunge
> in MAP, but the FCO doesn't look like it begins until just before you
> punched it again. Hence the lean glitch in the NB at 25:20-. What am I
> missing there? Can't be some sort of fixed delay to FCO, since it seems
> to go more quickly to cutoff when you shifted into 5th at 25:22. Please
> excuse the 20-questions, tasty bits of data you have there.

There are two different fuel cut schemes. One is a decel enleanment that
occurs when the throttle is lifted. The other is decel fuel cutoff (dfco) that
occurs during long decel. At 25:19 the afr spikes rich as the throttle is
lifted.
This is due to the drop in manifold pressure evaporating the fuel that
is wetting the interior of the manifold. Decel enleanment is also taking place.
That is the short lean spike at 25:20. I was back on the throttle before
it could get any leaner.

>
> Actually I'm surprised at how little rpm was lost in the 1st-2nd shift.
> Looks from the numbers like you dropped around 100rpm in that shift.

Shifted at 5775 and dropped to 4100. That is the 2nd to 3rd at 25:20.

>
>
> Are you using 8bit for everything, so the rpms are scaled by what X? If
> you are using 10240 rpm = 256, that would make your resolution 40rpm/bit,
> or 8096 rpm = 256, then resolution would be 16rpm/bit, wouldn't it?, but
> it looks like its in steps of 25rpm in your data. How did that happen?
> During post processing? Just curious.

All data except for the WB AFR is from the ECM. The rpm is by 25 rpm
per bit. The ECM uses an 8 bit ADC. This is for stuff like MAP, O2 mV,
TPS, etc. The WB controller output is read by an 8 bit ADC with a Vref
of 4.096V. This gives 16mV per bit. Good from 1.4Vout at 10.08:1 to
4Vout for free air. Post processing clips the WB AFR at 25.5:1 max.

BobR.

>
>
> Tnx,
> Brian
>

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