Autosport Labs

I've thoroughly confused myself as to what signal a tachometric fuel relay sees at the -ve teminal of a conventional ignition coil. I was thinking if you were to run MJLJ on a car equipped with K-jectronic injection for example, using one user output set to come live at a very low engine speed, say 200rpm, that could be used to replace what would normally be the coil's -ve signal. Then I thought maybe you'd need a small reed-type relay so this output would switch what normally goes to the coil -ve straight to ground.

I wish my brain wouldn't make me think thing like this then pause halfway through! Any ideas?

the K jetronic tachometric relay sees the same signal from the coil -ve as the rev counter... i.e. in a conventional ignition setup, the contact breakers opening and closing giving the flyback pulse.