2stroke1971

Just need some clarification.....

So, the crank turns three times per a rotor's complete revolution right?

two rotors on a 12a....

The tach for a 12a reports RPMs...of the crank itself right?


IM trying to get to how many ignitions (LEADING coil) per revolution of the crankshaft...
Two right?

IF a given coil is rated at 6500 rmps, with it's typical application being a V8, which is 4 fires per rev, thats 26,000 ignitions per rev, so if the leading system on a 12a is only firing twice per crank rev, that should be adequate I would think....even at a bit higher RPMs....


just pondering some ignition stuff...and while Im on the subject, Ive read about direct fire mod "giving the coils more time between fires"--I dont get that because of the typical waste spark arrangement, sure, you have a coil for each rotor, but they are each firing twice as much as they need to so wheres that extra time coming from?

j9fd3s

iTrader: (3)

you're right. the 3 sided rotors are geared 3:1 to the Eshaft. we measure RPM of the eshaft.

since there are 3 working chambers per rotor, and they spin at one 3rd engine speed, there is one power stroke per rotor per revolution of the eshaft. piston engines take two revolutions, because they are lazy.

this means a 2 rotor has a power event every 180 degrees, just like a 4 cylinder. the 3 rotor is 120 like a v6, and the 4 rotor is 90 degrees.

with the distributor the coil does fire twice per revolution, and when we do the DLFISH mod, it still fires twice, we just skip the cap. since supply voltage stays the same, and the dwell is the same, any additional ignition power is just from a bigger coil.

with EFI we can run 1 coil per plug, so then we can get more charge time. or you can run CDI