RPM Input to ADL from Honda CBR Ignition Module

[niceguysfinishlast]

Hi all,

Even though this is a question about an older ADL, I beleive it is relevent for the ADL2/3 and other ignition system combinations as well.

I am using the logger/display on a 1989 Honda CBR 600 engined vehicle. The only RPM output the standard ECU has is the low side driver for one of the two coil packs (wasted spark). This was originally used to trigger the standard Honda Tacho, but I was wandering if it is safe to use it as an RPM input on one of the ADL digital inputs (considering back EMFs and the like).

Does anyone have any ideas?

*Latest*
I have just had a play around with an occilliscope during cranking and my proposed input (coil negative side drive) is seeing back EMF voltages of 200v upwards, as the coil is switching on and off. Is this safe to use?

Thanks

[OmarK]

The best way to measure the RPM of your motor, is to install a crank trigger wheel and a hall sensor. This will ensure it is safe and accurate for the ADL.

[Holmz]

...
Does anyone have any ideas?

I bought an MSD device a while back that converts the signals on the coil input to a tachometer output.
That might be easier and cheaper - but probably heavier and not as elegant as a crank trigger.

[niceguysfinishlast]

Hi all,

Thanks for the replies.

I know the MSD product you are tallking about. I have managed to make my own using zener diodes and a solid state opto-isolated relay, and some other components. It works very well and only cost a few £'s to make.

A hall effect or similar on the crank is quite difficult to implement on the CBR (and other motorbike engines) without affecting the sealing integrity of the crankcase or any of its covers.

[Holmz]

Hi all,

Thanks for the replies.

I know the MSD product you are tallking about. I have managed to make my own using zener diodes and a solid state opto-isolated relay, and some other components. It works very well and only cost a few £'s to make.

A hall effect or similar on the crank is quite difficult to implement on the CBR (and other motorbike engines) without affecting the sealing integrity of the crankcase or any of its covers.

Do you have a list of parts and the schematic?
That would be a brilliant way to close your post!

[niceguysfinishlast]

I'll dig out the drawings and post them up here as soon as I can.