electronic ignition

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Fri 7 Sep 2001 08:45
electronic ignition - mike harvey
Can any one clear up a query for me please? On a distributorless ignition system, my understanding is that a notch on the flywheel/crank or whatever, depending on the model, passes a sensor which sends a signal to the ECU, which in turn earths the coil circuit, and a spark is delivered to the plug. What I'm struggling with is if the engine speeds up, and more ignition advance is needed, you cannot get the spark any sooner- as the notch has not reached the sensor yet, and the flywheel cannot advance. On an old distributor system, the advance is mechanical, and the points can open sooner. Is there some sort of delay built in that reduces with engine speed?
Thanks,
Mike
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Fri 7 Sep 2001 08:53
Re: electronic ignition - Michael
to the best of my knowledge, the spark is controlled by the ecu. The sensor on the flywheel is one of a number of inputs to the ecu that it uses to determine the appropriate time to intitiate the spark.
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Fri 7 Sep 2001 08:53
Re: electronic ignition - Adam Going (Tune-Up Ltd)
Mike,

On these systems the ECU controls the advance curve in response to various factors - revs, coolant and air temp, throttle position, inlet vacuum and so on. The flywheel or crank sensor is merely an initial refernce point used to establish crank speed and the position of No.1 cylinder (although some engine also have a cam sensor for this).

The ECU programme contains a "map" which plots the best ignition setting for all possible combinations of engine running condition.

Regards, Adam
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Fri 7 Sep 2001 09:13
Re: electronic ignition - andy bairsto
well explained adam,I could not have said that so plainly in a month of sundays.
andy
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Fri 7 Sep 2001 17:22
Re: electronic ignition - Adam Going (Tune-Up Ltd)
Thanks Andy !! Comes from the Editor of the local paper for which I do a weekly column continually telling me to keep it simple for the readers !

Regards, Adam
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