Time Attack - Oops i did it again

[gambler]

Robin - Thanks for that, I will get them to have a look at shielding the wires as we were having a problem with the car starting when the coil pack leads were too close to the wiring loom. It does look like it is not spark related as the misfire was starting at just over 1 bar of boost. The new ecu is possibly more sensitive to interference.

[robin]

It could just be that you reach the edge of some condition at 1 bar and the noise takes you over the edge.

The ignition (spark) circuit is the primary source of electrical noise as the operation of the coil requires producing 400V spike on the low tension side.

Really modern engines (i.e. not the Rover K-series ) have the ignition amplifier built into the plug top coil too; in this case the signal wire to the spark is just a control wire with no substantial current flowing in it and then it's much less likely to be an issue.

Cheers,
Robin

[gambler]

Thanks again Robin. I have passed on your posts to the guys at the garage, they agree with your idea of some kind of interference. I am pretty sure that the ignition amplifier is not on the top of the coil and is somewhere on the inner wing. We will be fitting new Plasma Projects coil packs this week as they have just come on board as a new sponsor.

[robin]

You say "the coil" like it has just one. I assumed the car has no distributor and so uses either wasted or sequential spark? If you cannot get to the bottom of it, feel free to have someone send me a wiring diagram plus ECU manual or whatever you have for it ... maybe I won't be able to add to the findings so far, but it won't hurt (or cost) to try.

Cheers,
Robin

[gambler]

Thanks again Robin. I will get a hold of them and send it to you.

The car runs 4 individual coil packs which sit in behind the spark plugs and I think that they run on wasted spark.... that rang a bell, i can check on that though.

I will be speaking tomorrow, so i'll sort it out then.

[robin]

Cool ... makes sense (except that wasted spark is not normally done with four coils, just two, but there is no reason not to do it with 4 if you have them).

[Peter]

Cool ... makes sense (except that wasted spark is not normally done with four coils, just two, but there is no reason not to do it with 4 if you have them).

Robin, is wasted spark where you perhaps have 1 coil feeding two cylinders (at different strokes)? i.e. 1 fires on the compression stroke whilst the other fires on the exhaust stroke and hence is 'wasted'? Then the opposite occurs on the next cycle?

[robin]

Wasted spark is when you fire two cylinders of a four stroke engine at the same time. One is on the compression stroke so explodes. The other is on the exhaust stroke so doesn't care whether or not you spark.

It was done originally to make distributor-less ignition systems cheaper - only two ignition amplifiers, two coils, etc. vs. four. The other advantage of wasted spark control strategy is that you don't need to know which phase the engine is on - so you know which pair of pistons is rising from the flywheel position, but you don't know which way the cams are facing, so no need for a cam position sensor. Of course most engines use sequential injection where you need to know the cam position.

Once you have four coils you can either wire them in parallel pairs and still have wasted spark or you can drive them individually.

Cheers,
Robin

[Peter]

I think I was on the right track then.

Thanks!


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