Performance testing with VEMS

[dnb]

I need to do some performance testing on a couple of cars.  One is my TVR, and the other is a friend's TVR.  Mine has VEMS already and his doesn't yet.  We planned to fit a trigger wheel to his car so my spare VEMS could do data logging, but his wife is beginning to add up the cost of TVR ownership...

Is there a nice and cheap way to get a trigger input to VEMS using something like an inductive sensor on an HT lead?

All I need to do is monitor RPM with a reasonable degree of accuracy.  The rest is maths.

[cliffb75]

Can't you just splice off the tacho drive signal?

[dnb]

The tacho drive signal on a TVR is nasty - it's an inline resistor from the coil and I'm a bit nervous about using it!

[Bat]

Hi,
I see your point, but Rover used it to trigger their ECU .....
Don't know if that's a good or bad thing, but it certainly worked.
Cheers,
Gavin :)

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What about a bit of Zener diode protection?