Originally Posted by stevieturbo

4 tooth crank gives very very little resolution or information to the ecu. It only denotes a TDC event. It cannot distinguish which TDC event though, and in between the teeth.....it's just a waiting game...oh next tooth....wait....oh next tooth

A 36-1 at least gives info every 10deg of rotation and with the missing tooth, gives an identifier for a pair of TDC events. Still lacking, but much improved resolution for crank position and speed. But can still only tell cyl1/4 TDC, not which one is actually on compression/firing etc so can only fire them together, wasted spark, a spark always firing on an exhaust stroke which is a little pointless.

Hence a phase sensor is needed....preferred, this can then tell the ecu, the next TDC event will be cyl1 compression. This then allows proper timed sequential injection events, and one spark per cylinder.

So for ignition the Cossie gets away with things via the distributor for ensuring the right cylinder gets the right sparks ( because the 4 tooth crank cannot ), and the 2 tooth trigger in the dizzy is to indicate where cyl1 is for the somewhat timed injection events.

I wouldn't necessarily say a 36-1 would start any faster or slower than the 4 tooth. It depends on the overall configuration.

Potentially, the 4 tooth/dizzy could initiate starting after any one of those teeth, which happen every 90deg of crank rotation. Whereas the 36-1 only gets that identifier, worst case scenario, almost 360deg of rotation.

4 tooth and no dizzy ( for spark distribution, but used as a phase sensor ), would not be able to attempt to start until the phase trigger has been seen. So worst case that might take a full 720deg of rotation, again worst case.

Of course thereafter a multitooth wheel offers the ecu better resolution as it's always seeing lots of teeth to know/count exactly where the crank position is.

But no need to do dumb shit like Nissan did and have a 360 tooth optical wheel, then mount it on the bloody camshaft after a wobbly belt driving it !!! Madness.