How does MJ know which time around?

[Jeffs_Alpine]

Hey all,

I'm sure there's a very simple answer for a questions that's been eluding me this morning, so I thought I'd throw it to the wolves... er, ah, I mean the group.

Some background: I've got a 67 Series V Alpine motor. A 1725cc for anyone who cares. I just finished rebuilding the motor and have had it running with a standard distributor. I know, how archaic.

My crank, like most 2-stroke motors I'd expect, spins around twice for a complete engine cycle - all 4 cylinders firing: intake, exhaust. So I guess my question is: how does the MJ know which of the two possible cycles the missing tooth starts in?

I ask the question cause I've just swapped out the disty for the MJ for the first time.

But, when I swap out all of the wires, in the correct firing order for the car, starting with 1 (obviously), it backfires rather badly. I've had the disty in 180 degrees out before and it kinda sounded like that.

So, how does the MJ know when it starts if the plug after the missing tooth is 1 or 4 (my firing order is 1, 2, 4, 3)? I can intuitively sort out everything in the system but this one issue.

Does my question make sense?

Thanks - Jeff

[BRUCEROE]

The crank trigger systems use "waste fire", which means they fire every revolution. Like lawn mowers. The unneeded spark at the end of the exhaust stroke does no harm. To make the system a lot more efficient, the 2 ends of an ignition coil secondary are connected to 2 cylinders that reach top dead center at the same time. One will be at top of the compression stroke when the other is at the end of an exhaust stroke. Next crank revolution their states are reversed. A coil is needed for each 2 cylinders, for an even fire engine. The exhaust stroke doesn't have much pressure, so not much spark energy is lost there. No energy is lost at a distributor rotor gap, no distributor. Bruce Roe

[Jeffs_Alpine]

Hi Bruce,

Thanks for your great explanation. I wasn't sure I'd stated the question well.

So, walking through the two cycles, with my firing order of 1,2, 4 and 3, the first 1/2 cycle fires cylinders 1 and 4, where 4 is the dead fire. The second 1/2 of the first cycle fires 2 and 3 and 3 is dead. The first 1/2 of the second cycle again fires 1 and 4 but this time 1 is dead, and finally, in the last 1/2 of the second cycle cylinders 2 and 3 fire and 2 is the dead fire.

Now, having worked that out in my head, I've gotta go back and check my wiring into the coil, since it's backfiring like a big dog.

Thanks again!

Jeff