Divide by 6 frequency divider

Hi all. I'm new here, but looking for a bit of advise. I have a Smiths rev counter that is designed to work with a petrol engine ignition system, putting out 2 pulses per revolution of the engine. I'm trying to get it to work on a diesel engine, by driving it from the rev counter terminal on the alternator. The only problem with this, is the alternator is a 12 pole unit, so puts out 6 pulses per revolution, plus it is driven at twice engine speed. I've decided the easiest way to get it to work would be to build a divide by 6 frequency divider circuit. I've found a generic diagram for the circuit here http://www.ecelab.com/circuit-frequency-divider.jpg However I'm not sure how to configure it to divide by 6. Any ideas on this would be appreciated. I also presume that I would then need to use the circuit to trigger a transistor, as I think the current drawn by the rev counter (An inductive type) would be higher than that 555 timer could supply. I'm not sure on connecting these up, though from what I can see, the output from the frequency divider would connect to the base, +12v to the collector and the emitter connected to the rev counter.
Any thoughts on this problem would be greatly appreciated.
Thanks
Andrew

 

Actually, that said, I'm sure the rev counter has a 6 cylinder setting. If I were to use that, I would only need a divide by 4 circuit, so could use 2 divide by 2 circuits, the output of one being the input to the second one. Even so, I'm not sure exactly which components I should be using to make a divide by 2 circuit, as the first diagram shows a range of values.
Thanks
Andrew

 

Ok, done some more research, thats not going to work...
I'm now planning on using a hall effect sensor and a magnet on the crank. Again though, I'm not sure on the circuitry. I presume I'd need the hall effect sensor to operate a transistor. Any help will be greatly appreciated.
Andrew