I believe Electromotive EFI decades proclaimed the advantages of the 60-2 wheel to their system, in that it was a more "continuous" measurement of the crank location. It seems today at very high rpms's, higher then I am considering the 60-2 might be data overload for the ECU. Megasquirt 3 Pro offers a choice in set-up for the two and other options. Does anyone know if the Megasquirt for instance measures and utilizes all 58 teeth in ECU timing calculations, making a 60-2 tooth wheel more precise and therefore a better choice? I will contact Mega and others, but want to do my homework first.

The 60 tooth has resolution to 6 degrees vs 10 for the 36 tooth. MS does account for every tooth, and according to this page both have been bench tested to 18,000 RPM. This was good for the MS2, so I'm sure MS3 can do that with no sweat. Probably no real advantage unless you require ultra precise timing.

Maybe there is a bosch white paper (since they invented all this stuff anyway) out there someplace that explains the reasoning for the 60-2. Seems either option will work well. I used a 36-1 on mine just because you can get ford 4.6L parts in every parts store or wrecking yard in the U.S. for next to nothing. I'll look and see if I can find the right bosch training manual at work tomorrow. I don't remember what system the 60-2 was introduced on.

We started with a 60-2 wheel on our stuff and now use 4x flying magnet MSD wheels with a hall effect pickup.............no difference whatsoever.

Monte

Absolutely NOTHING wrong with a 60-2 wheel...........will you see any advantage with it or have more control of your spark timing.......nope.

And lets talk about "significant" control. I run a 738" engine with 4 stages of dry nitrous in "closed loop". I set my target and let the box do its job and correct. On nitrous motors, 1 degree of timing one way or another can mean a record run, or an ash try. When we run stuff "on the edge" looking for that last little bit, we deal in HALF degrees. Never had a problem with the 4x wheel.

You MIGHT and I repeat MIGHT have less crank time with the 60-2, although it made no diff in our crank times. If you were running batch fire or bank to bank, with no cam sensor, I might see where the 60-2 could help...............but in sequential.......nope, can't see it

Monte

If you're in doubt wether to use 36 or 60-wheels, I think you should also be worried (more) about individual cylinder-to-cylinder timing events and adjustments.

Not every cylinder(head) is a perfect copy of the one next to it, and not all cranks are ground precise enough to have the rodjournals at a spot on perfect 90°, so it most likely that some cylinders in an engine would like a degree or more different earlier/later ignition-adjustments to make optimum power. We're talking EGT and lambda measurements for each seperate cylinder aswell here.

Some tech:
After the ECU sees a crank signal it uses the previously computed engine RPM (based on the time/distance between crank pulses) to compute the time for the next ignition pulse.

At a steady RPM this was never an issue, since the new RPM will match the old RPM. But during acceleration the computer is, by definition, late in it's timing calcs. In days of slow computers this caused a slight transitional retard only during rapid acceleration. So basic physics suggest that the more crank signals you have, the more accurate the ignition, but with today's ECUs, even 4 pulses per rev is usually more than adequate.

The OEMs went to high resolution crank wheels for OBD2 misfire detection....as Monte said- we don't need it.

I understand your point, but am still puzzled, then did the "old" ECU's take over 90Deg to calc the new accelerated rpm, no matter the tooth count? And the new ECU's cannot now account for any new acceleration with 4 magnets for at least 90 deg of crank rotation, no matter how fast they do the calc's, since it takes a starting pulse and the next timing pulse for an rpm calc, at the minimum, which on a 4 magnet wheel is 90 deg, correct? It seems odd so many companies offer much higher toothed aftermarket timing wheels in often race use, and there is no reported advantage. I guess I should be soon seeing that dead horse.

Yes the horse is dead With 4 pulses per rev the ECU had about from 20 to 80 degrees to calculate the timing, depending on where the reference pulse occurs. That gave the ECU (old or new) plenty of time to do the calcs, but the crankshaft is accelerating during this time so although the calculated timing was correct the crank itself has passed.

With 60 pulses per rev the ECU just counts the pulses from the reference notch until it get to the one closest to the required timing (no calcs, just counting). Then it has only 6 degrees of time to compute the result. You need a faster ECU for that, but today that's ANY ECU.

"(no calcs, just counting)"

That's the heart of the question, Thanks.