calculate RPM and crank position,with distributor signal.

[settra]

hello forum. i am in the procces, of converting my car , from carbiratur, to Fuel injection !! ..
1) i would like, for the start, to keep the ignition system, as it is, and not control it from the ECU...
2) now to my problem... My car, is a 1992 Audi 80. (1.6 lt). it seems, that it has no, crank position sensor.
the only signal, relevant to my rpm, that i can get, is from the distributor. the distributor has a plug with 3 connections. +,-,sig. the sig connector goes from +12v to GND, as expected...

the thing is this : how is this signal, associated with my crank exact position??? i am not sure if my distributor , is a break points, or it uses a hall effect sensor! (but if i remove the 3 connection plug, the car does not start) anyone can help ???

[settra]

also. the car uses a 3wire ignition coil. so the coil receives signal from the ecu , to produce the spark...

[russian]

You have to be more specific, what is your question exactly?

Can you control the ECU only with a cam signal? Yes absolutely you can.

In all 4 cycle engines cam turns at 1/2 crank speed. So, cam speed gives you crank speed

Crank position is a different story - I guess you would need to set your engine at TDC and look at the sensor position if you can open your distributor. Maybe someone know this but this is specific to your vehicle.

Do you know the voltage on the sig wire? If it's 5v I think you should use a cheap logic analyzer to sniff the signal.

[settra]

well, by now, i have llearned more things. so yes, my question would be "can i run injection on cam signal only"

the thing is this: the signal of my distributor is constant 12v, and goes low when "signals" , if i mesure the pulses, then , at iddle , the distributor gives 1000 pulser per minute !! .... but what is this supposed to mean??? that my rpm are 2000??? or that the distributor gives signal about crank, and not cam??


last: is just one signal : "X degrees before TDC", enough?? i think yes, cause all the other positions, can then be extracted via mathematics....

[Fred]

well, by now, i have llearned more things. so yes, my question would be "can i run injection on cam signal only" ;)

Yes.

last: is just one signal : "X degrees before TDC", enough?? i think yes, cause all the other positions, can then be extracted via mathematics....

Yes, with the right strategy, but timing is less accurate under dynamic conditions this way.

[settra]

cool. i am only interested in the injection for now... (ignition will be from the cars ECU).
if i use a segmented disk, and a VR sensor, then the timming will be more aqurate, correct?? (basically i was thinking to use, an optical sensor, with a DIY disk, mounted on camshaft pulley)

[russian]

last: is just one signal : "X degrees before TDC", enough?? i think yes, cause all the other positions, can then be extracted via mathematics....

Yes, with the right strategy, but timing is less accurate under dynamic conditions this way.

I wonder if ignition while cranking would get challenging with one reference point per shaft revolution?

Injection is much tolerant to your precision obviously.

[settra]

well, it would require , that the engine, makes a full revolution before it starts injecting, but i dont think it will be such a problem?? you can do an asychronous inject, anyway when the crank signal is received??

[russian]

Sorry I was vague

My concern is about lame timing precision since RPMs do change quite a lot, cranking RPM is not constant for sure.

[settra]

so you mean, that etc:

the first cylinder will have good timing,
but then, when its time to spray the second, or even worse, the 4th, the rpm , will have change so much, that it will be dificult to get the correct timing??