Trigger wheels

It was mentioned in another topic briefly about setting up trigger wheels and has left me wondering.

On a 36+1 trigger wheel does it matter where the missing tooth is and where the sync trigger happens?

I'm guessing you are referring to 36-1 which refers to 36 evenly spaced teeth with one missing?

In the ECUs I'm familiar with the location of the missing tooth isn't critical as the offset or base timing can be adjusted to account for the location. The sync tooth location needs to be locates anywhere except the missing tooth. Normally you would try and align it so it occurs completely opposite the missing tooth.

Yeah, that's what I was meaning.

What does the sync signal actually do then, I thought it's location was a bit more critical

The Sync signal tells the ECU which cycle (ignition or exhaust) it is on. Since there are two crank revolutions per cycle this has to come from the cams which move at half the speed of the crank.

Chris, the sync pulse is critical and there are some ECUs (generally older technology) where the location was important (some required the sync input to occur 60 degrees BTDC on the compression stroke for example). Most modern ECUs now don't care where the input occurs and the offset (crankshaft angle between the sync pulse and TDC cylinder 1) can be programmed.