mk1-forum.net

This relates to one of my other projects but I imagine the principles are no different with a Mini engine.

I have converted the Lotus twincam engine in my Elan to run wasted spark ignition - Ford EDIS, trigger wheel, coil pack, TPS, Megajolt etc.

I had my tachometer converted to RVC from RVI by Speedograph Richfield. The system works brilliantly but I'm bu66ered if I can obtain a suitable signal to drive the tacho. I have tried the suggested pins on the EDIS, inc pin 11, without success. I have tried the dedicated tacho output on the Megajolt - this gives nothing except for a big spike when I kill the engine which momentarily sends the needle around the dial and then back to zero.

I can see from the internet that this issue is not new - everyone seems to have issues getting the tach to work with this system.

I am a bit stumped with this one - are there any ignition wizards out there who can make suggestions? I've tried Speedograph but they can't seem offer any advice.

Cheers, hopefully.

Jon

Better of on the Turbo mini forum, lots of people use that system on there

Sounds like you need to use the diode trick, details on the autosports website.
Under: Interfacing to Tachometers

http://www.autosportlabs.net/MJLJ_V4_ve ... guidelines

My mate is running MJ on his Midget, here is what he had to say, hope it helps...

I used a tacho feed from the PIP out of the megajolt - just spliced into the wire.
My RVC tacho was converted to RVI, and this needed a +12v feed (which goes to one of the old bullet terminals), and then there was a new terminal which took the feed from the PIP.
I added an extra earth, didn't want to rely on earthing through the case.

Thanks for your comments/suggestion chaps.

I tried the diode driver without success.

I eventually traced the issue to a poor earth on the tachometer. Now running perfectly on the 'clean tach' output of the Megajolt.

Jon