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Re: Motronic question
Earlier, DeWitt Harrison wrote:
>
> In the CIS systems, there is a basic CO adjustment that
> insures the mixture control system is operating about
> the center of its control range in closed loop. For example
> some, maybe all, of us CISers can set this by monitoring
> the duty cycle of a mixture control signal without resorting
> to actual CO measurement.
I think the only 'mixture control signal' like you are describing
is the O2 sensor output. The O2 sensor output can vary from roughly
0 to 1 volt, and will usually oscillate between 0.4 and 0.6 volts
as the sendor's signal is interpreted and mixture adjustments
are made.
CIS systems usually include a CO adjustment, like the small (3 mm?)
allen screw in the arm holding the air flow measurement plate
in air flow controlled CIS systems. Adjustment capabilities were present
even before O2 sensors showed up on the scene ... O2 sensors came out
when catalytic converters were installed -because the cat converts
needed to have the mixture exactly right for them to do their job.
>
> The big question is do the Motronic systems of the
> same late eighties era have an analogous situation
> and means of monitoring the control loop without
> CO measurement? Major Bosch guru points potential
> here.
There are certainly O2 sensors on late Motronic systems, and you can
watch their output signal with a very high impedance volt meter.
There are small voltmeters made that have 10 LED's, that show 0-1 volts
in 0.1 volt increments. Be careful not to turn on the ignition while
the O2 sensor is disconnected, the ECU can end up storing a fault for
faulty O2 sensor, and then defaulting to a limp-home mixture map
instead of using the O2 sensor signals. I had this happen once on
a BMW Motronic system.
- Charlie
Charlie Smith charlie@elektro.cmhnet.org 614-471-1418
http://elektro.cmhnet.org/~charlie/ Columbus Ohio USA
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