Re: Uh oh - 'what car' car opinions sought - BMWs

In article <gc3gh4$84i$2@xxxxxxxxxxxxxxxxxxxxxxxxx>,
pete.murray@xxxxxxxxxxxxxxxxxxxxxxxx says...

Lambda sensors? On my Range Rover? Um. No, there aren't any of those.


For the new adaptif ECU's a plug is welded on the first part of the
exhaustcolletcor (as near to the engine as possible and before the
catalysator). It will receive the wide band Lambda-probe.


It's also running two ECUs. The original Lucas job and a custom made
Zytec system that runs another map for the turbo and it's associated
gubbins.

At best your modified ECU is configurated on a rolling road during a 2
to 4 hours-session. The operator first checks if the car runs and starts
fine (when cold/warm) and then tries to get a cood combustion and dito
power on the rev-range. The part where the turbo gives no boost will be
the same as the orignal engine-settings.

That implies also that your map is static and will not adapt to new
situations, use, aging, different fuels etc. Keeping in mind the very
low number of turbo'od Range Rovers it is highly unlikely that the
modified map is rather complex or that programming on lesser loads is
done (most rolling roads don't have 4x4 capacity and they definitely
don't like big power turb'od engines for long durations under load).
Half load fuel flow will be half of WOT fuel rate, and so on.

A fuel map in a mass production car takes about 1500 Hr of testing to
complete, again low volume cars tend to have less optimised maps in
order to avoid that cost and because after all the owners of those car
are less bothered by fuel consumption.


Having said that, last time I had it hooked up to an emissions analyser
it was running remarkably sweetly, but wasn't under load.


Without load, the turbo is not activated, your engine is basically
standard and the emissions are those linked to the idling settings set
by the constructor of the engine.

I have to say that the new "self-learning" ECU's are quite impressif and
it is surprising that manufacturers haven't jumped on the wagon yett.
Their orginal mapping is considered to be good for all engines
regardless of tolerances. This is fine but it leaves 5-10% power
sleeping in the engine and -on the worst cases - 20-25% in fuel
consumption.

On new cars these less-than-optimum-maps doesn't show up on exhaust gas
analysers as the cats reduces CO-values and unburned gases to zero.

The self-learning ECU finally give feedback about the quality of
combustion whereas is the stone ages we just changed a calibrated
orifice in the carb and hoped for the best.

In the middle ages some of us got their dirty hands on programmable
ECU's and computers. That was a mayor step (our hands got clean in the
progress ;-) ) but still the map was depending on extensif testing and
only correct on the time of setting up.

Finally we are here and today: the new ECU start from a basic map and
modifie themselves, leaving the time to go to the pub! We don't drink a
lot though: as with all new toys these Ecu's tend to be expensif.


Tom De Moor



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