crank triggers?

is there any particular reason other then packaging why crank triggers are sized the way they are?


example:


two crank triggers, one 80mm diameter, one 140mm diameter. the notches on both wheels are the same size in degrees


I could see where going smaller might cause problems, with the sensor not being able to pick up the gaps, but is there any reason a larger trigger would be a problem? seems to me like a larger sensor would be desirable, as the larger gaps would be easier for the sensor to pick up.

Edit:

I realize now that this post would probably be better in EFI systems instead of OBD2, feel free to move it if necessary.

I did not see any differences in the diameters when I designed my '0411 PCM crank triggers. I designed one of the crank triggers to work on the bench 2x the tooth count so the crank and distributor speed were matched. The other crank trigger is on the engine. I think the more important factor is the response time of the sensor itself. The faster a sensor can respond, the smaller the trigger wheel can be in diameter.

dave w

well for my application, I would be making a 24x wheel, and I would be making it bigger so it would slip over a crankshaft(approx 7" inches around), and all of the 24x wheels I had seen appeared to be about 3" now all I have to worry about is the sensor position in relation to the crank. hopefully it's pretty close between my engine and the donor engine.

Using a larger 24x wheel should be fine. The response time of the sensor is less critical as the trigger wheel increases in diameter.

dave w

I was thinking that, just wanted to make 100% sure before I continued going down that path.

Thanks for the help!