LAMBDA CONTROL 101/102...

[Jim Conforti <lndshrk@xxxxxxxxxxxx>]

Since Mark asked..

OK.. first you need to understand how the DME decides how much fuel it's
going to squirt..

Air is measured by either an AFM or HFM/MAF and the voltage is interpreted
by the DME and linearized into a number.. Q (kg/hr of air)

>From Q and n (rpm) we make the basic LOAD calculation as follows:

Tl (tee sub ell) = Q / (n * Ki) where Ki is the injector sizing constant

Once we have Tl we need to make Ti (tee sub eye) or injection time by adding
in and multiplying in a bunch of corrections..

One of which is the factor from the "maps" (which is really a 1.0 based
multiplicative correction).. then there are accel and decel and temp and
start and post-start and.. (well you get the picture)..

Last but not least is .. (tada)

Lambda Adaption.. where the base Ti number is corrected via a small additive
number (determined by the O2 at low load/idle) and a 1.0 based mult. factor
determined at higher load/rpm.. 

Even if we are at full throttle and the O2 sensor is OFF.. these two numbers
are still part of the calculation.. the only time they revert to +/-0 and *1
is when the adaption is cleared by powerloss (OBD-I) or command (OBD-II)

The actual O2 sensor isn't even used yet..

Now.. once we HAVE the Ti signal.. and IF we are in the conditions of Lambda
Control.. we attempt to cycle rich/lean by slowly running the Ti higher and 
lower in a closed LOOP.. if we notice we are always going more lean.. i.e. we
are too rich.. we see where we are running and either reduce the additive or
multaplicative adaption.. and vice versa for always being lean.. 

At full throttle.. we stop the actual rich/lean seeking.. and we don't attempt
to continue to ADJUST those two numbers.. but they are still USED in the
base fuel equation.. 

What this means is that if you muck with part throttle you cause problems
because eventually it adapts out the richness you put in.. and the WOT now
goes too lean for safety.. 

Example: If you added a blanket 5% to the part throttle only.. soon the part
throttle would be back to stoich. and the WOT would now be 5% LEANER!

Because the ADAPTION would go lean on you..

Yes.. it's complex and counterintuitive.. but it IS the way it works..

And all BOSCH BOOKS talk about is the actual rich/lean seeking of the sensor
which is in reality the LEAST part of the equation in total.

Jim C.

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