No subject
Thu May 30 05:48:45 GMT 2013
is
pretty bad. Bottom line is that MAF costs more and doesn't work as
well
at WOT... compared to well tuned speed-density systems. The
question
to ask is does the esier tuning outweigh its other disadvantages?
--
Jonathan R. Lusky -- lusky at knuth.mtsu.edu
"Turbos are nice but I'd rather be blown!"
68 Camaro Convertible - 350 / TH350
80 Toyota Celica - 20R / 5spd
=====================================================================
> In the prototype controller, AE should simulate the accelerator
pump of a
> traditional carburetor. That would make it an additive term to the
equation
> of (1.2.2) that would add a pre-set quantity of fuel as a function
of
> throttle change. Additionally, it would have an adjustable "decay
parameter"
> that would be similar to the hole diameter of the "shooter". In
the future,
> it may be beneficial to include MAP and coolant temperature into
this
> term. For now, I will just represent it as a yet to be defined
additive
> function of AE. (need more info here --- need to define the
controlling
> algorithm)
It's actually pretty important to have the 'shooter size' and 'decay
rate'
controlled by engine temperature.
I've seen systems that have two accel pumps: one for delta MAP and
the other
for delta throttle.
Ideally, you would model the fuel thickness in the intake manifold
between
the injector and valve, which would require air temp, manifold temp,
manifold
vacuum/pressure, and probably an estimation of the willingness of
the air
to accept the gasoline as a vapour. This is something for someone
who has
done research on this area... if you can model it, you don't have to
spend
as much time tuning...
> 1.3.2 --- Deceleration Enleanment (DE)
>
> I don't believe this term is necessary in the first prototype of
our
> controller. Ultimately this term will lean the engine during
deceleration
> much as the acceleration enrichment term adds fuel during
acceleration. It
> should have the same inputs as the acceleration term.
Exactly. Just acceleration enrichment turned around. It only adds
about
fifty or so lines in my code (assembler). Makes a big difference when
you're coming out of a corner and you don't have to let the engine
cough
out the raw gas it sucked in on the overrun.
> 1.3.3 --- Close-Loop Feedback (CLF)
>
> This should be a multiplicative term representing the integrated
error from
> the oxygen sensor. The conditions for when this term should be
included are
> yet to be defined. Conditions to consider are cold O2 sensor, cold
engine,
> acceleration, deceleration, power enrichment. (others?) (need more
info here,
> need to define the controlling algorithm)
Actually, I've seen it done as a combined additive and
multiplicative term.
The short-term feedback (oscillator) is additive, the long term
(block-learn)
is multiplicative. I guess this simplifies control calculations...
Most FI software I've seen has a lot of compensation for the
temperature
effects on the O2 sensor. A lot of engine control software attempts
to
predict the temperature of the exhaust and the exhaust system
components
to compensate for this. I thought it was wierd, too...
-Dale
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