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Reluctor / rotor phasing.

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Hi- Im running a V8 with a distributor and just have it running on a stand through an Atom G4+ . Its miss firing badly as I rev it above 2000 rpm and now im questioning the rotor/reluctor relationship . My question is in relation to say no1 cylinder does the ecu only recognise it needs to fire AFTER the number 1 reluctor point has passed the mag pickup ? Or Does it recognise that the no. 8 reluctor point has gone passed and no. 1 is coming up . The reason I want to know as I see it is it makes a difference to where I position the rotor in relation to the cap tower . Thanks - Ken.

What trigger mode are you using? If you're using tooth per TDC then the pickup alignment is important but for every other mode you can simply adjust the offset in the software so the actual alignment isn't critical.

The important part with a distributor based ignition system is to ensure that the rotor arm is just leaving the output button at the most retarded timing you expect to run (normally around zero degrees). This means that as the timing is advanced the rotor will remain aligned with the output button. If you get this wrong it's quite possible to have a crossfire within the distributor cap as the timing advances up.

Hi- Trigger mode is multi tooth so your explanation makes sense - Thanks.

Ok as above, the trigger alignment isn't important specifically with the multi tooth trigger mode as you can adjust this in the calibrate screen. The rotor arm alignment is an aspect a lot of people over look, particularly if they aren't very familiar with a distributor ignition system.

Need help - Problem is the timing wont follow the ignition map . With the whole map set to 20 degrees the timing climbs steadily up to 50+ degrees . The dizzy is a locked VR/Mag pickup using an msd streetfire box . I went through posts on this forum and found one relating to pickup polarity so I swapped the wiring with basically the same result . The runtime values show 20 degrees commanded timing and the ignition angle gauge on the tuning page shows the same . All while the timing is climbing with revs to the point of misfire/crossfire . Ive tried both multi tooth and one tooth per TDC modes with the same result . The timing wont lock even with the trigger calibration page up . The rpm reading seems reasonable and no trigger faults show up - Any ideas ?

are you using rising edge or falling edge on the trigger setting?

Perhaps there is a DC voltage offset in your trigger sensor, so the timing varies with the amplitude of the signal if the ECU is detecting the 0V crossing. Although a 30deg change seems unlikely. Can you hook up an oscilloscope to the trigger and see what the signal looks like?

Sorry don't have access to an oscilloscope . To Chris250 - I have it set to falling . Although I just re-read the trigger information and it said that some MSD ignitions require a rising edge ? Could it have the effect im seeing ? Basically an even but uncontrolled rise in timing with revs ?

It's highly likely, I would first confirm that yours is one which requires the rising edge then try it

Hi - MSDs do need rising edge and ive got mine set to falling . Ill change this and retry - Thanks for the reply .

Hi Chris250 - Problem sorted - you were spot on - Thanks . Just one last small problem - I cant get accel enrichment to work . Changed accel sensitivity and wakup enrichment and checked clamps but in runtime values no enrichment percentage increase shows . Consequently as I crack or blip the throttle it goes lean momentarily . Where do I start ? The engine is a 440 cid v8 using a 90 mm throttle body - no TPS just a MAP sensor . Thanks - Ken .

Glad you got it sorted.

Could you post a copy of your map?

You'll get a momentary lean spot, that is what the accel enrichment is to counter act. have you got your 'accel mode' set to MAP? default is TPS

Hi - Ive got this problem mostly sorted too . After reading a few posts on the forum and watching the accel enrichment tuning webinar I realised I had WAY to much enrichment . Also now the timing is sorted and the areas of the fuel map im running in seem reasonable ive been backing down accel enrichment and also clamp figures with great results . The engines response to cracking the throttle now is fantastic - it positively barks ! Streets ahead of the old carb ! Still just a small hesitation off idle but I think I can work through that but any tips are welcome - Thanks .

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