Posted: Wed Mar 19, 2008 9:27 am
If you have a scope then I would just use the engine for cranking and unplug the injectors. That way you can't hurt anything. Leave everything as is and resolve the dwell issue. During cranking you say the dwell is about 3 ms, so on the scope it should show as a very small 3 ms high value compared to the space between the missing teeth from one rev to the next rev, which should be over 100 ms during cranking. If it is, then you must have the correct output polarity. From what you have said, this is in fact what you see during cranking. Are you saying that things change drastically when you go past cranking rpm to idle ? That would be really surprising. Plus if MT is showing your dwell as -22ms, that is an indication the code and/ or data is really screwed up. If your msq is from when you first started, then you need to save the current msq and compare it to the one you posted. The other possibility is that you have a bad VR input and the processor is going in and out of synch on noise and firing erratically. Does the rpm show as as a steady and reasonable number during cranking and idle ? Are there any momentary flips to 0 ? More importantly, does the scope show the ignition outputs as consistently spaced - with a 4 cyl you should have 2 pulses between the missing teeth from each of the 2 ignition outputs. Also the spark edges from output 2 should fall halfway between the spark ed ges of output 1.
As far as there being no change in the spark timing when you change trigger offset, here are some things to consider:
In dual spark mode, spark must occur before tdc. If it doesn't, it is forced to occur, so if you are really way off then the spark will keep occurring at tdc. Also during cranking, if using trigger rise, then the spark will fire when the tach pulses come in regardless of table advance. The processor has no way of knowing where tdc is except from what you tell it. It assumes that tdc is on the tooth after the missing tooth plus delay teeth and as modified by trigger offset. But if, after considering all this, you see the spark for output 1 coming in x deg btdc and MT says the advance is x deg btdc, then your timing is probably correct and you should be able to change it by 10 deg and see it on the scope.
As far as there being no change in the spark timing when you change trigger offset, here are some things to consider:
In dual spark mode, spark must occur before tdc. If it doesn't, it is forced to occur, so if you are really way off then the spark will keep occurring at tdc. Also during cranking, if using trigger rise, then the spark will fire when the tach pulses come in regardless of table advance. The processor has no way of knowing where tdc is except from what you tell it. It assumes that tdc is on the tooth after the missing tooth plus delay teeth and as modified by trigger offset. But if, after considering all this, you see the spark for output 1 coming in x deg btdc and MT says the advance is x deg btdc, then your timing is probably correct and you should be able to change it by 10 deg and see it on the scope.
