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MG Midget and Sprite Technical - Rev counter

Anyone who now uses programmable ignition, how did you make your rev counter work??
Bob (robert) Midget Turbo

What ignition system are you using.
Duncan Hughes

Bob, I think they have to use a signal from the ECU normally. If I can find a Ford wiring diagram from the ECU plug I'll let you know, I should have one somewhere

Toby has a super electro-psychedelic display thingy on his dash IIRC

see pic

but well, I just dont ask! More wires than Sainsburys have rabbits...


Bill

Bob - I take the tacho feed from the EDIS module and feed it to the posh rev counter...

I'm not sure that a standard Smiths will accept that sort of feed - maybe some of the newer ones that are designed for the retro look might work better...
Toby Anscombe

just looked at Gwyn's Mondeo book wiring diagram and it loks as if our old friend "white with a black trace" is used as the counting circuit via the ignition module, is that how yours is signalled Toby?
Bill

Yes thats what I was dreading. Mine will not work from the output of the Alpha ignition system and I was hoping someone really clever would tell me a quick mod to make it work. I might have to buy a modern gadget and somehow fit it in the hole! :-(

Duncan I am using the Alpha weber kit.
Bob (robert) Midget Turbo

Bob has it got a signalling wire on it (in the dark here I'm afraid) that you could siamese the triggering signal off. It would still be a signal for every rev wouldnt it?

off to Google "Alpha Weber" now in seach of enlightenment
Bill

Yes it does have an output wire but I suspect that the signal voltage may be too low, but not sure what form the signal is.
Bob (robert) Midget Turbo

I suppose it will be 5v or less won't it?

Short of amplifying it it looks as if you will need to get a speciallised one, I'm sorry to say

I recently threw away (why? not able to justify hanging on to it with the gaffer!) a BMW instrument cluster that uses a low voltage (5v) signal, each insrument was capable of being removed from the fascia panel but as I haven't needed to keep it since I abandoned the BMW 5 speed project it was wasting space

The point is though most scapyards have loads of modern clusters that you might have been able to shoehorn into the Spridget gauge "body can".

Good luck Bob
Bill

I hadn't thought of that Bill. I could change the guts for a modern replacement couldn't I? Will start having a search around.
Bob (robert) Midget Turbo

Bob - whats your take on the Alpha management? has it got all the right knobs and tweaks?
Toby Anscombe

I assume you're using a Mondeo coilpack Bob?

Neither my EDIS signal nor the ECU signal would produce enough voltage to shift the standard Smiths tacho.

So mine is run directly off the two trigger lines of the coilpack using a three diodes and a resistor to produce a signal the same as a standard coil. Now works fine.

If this setup is what you're looking for I can do a simple diagram of it...
Bob T

I need to get a dongle to allow me to interogate it. At the moment I am booked in with Mike at Lincoln to do some set up work on the RR. It has 3 inputs and I have used boost pressure, trigger disc and inlet temperature. The car is running extremely well on the emergency map so hoping with set up it ought to be great. It also has the rev counter output and gear change light that I assume I will be able to set when dongle is aquired ;-)
Bob (robert) Midget Turbo

Do the simple diagram for all of us Bob


please
Bill

Bloody hell boys.... over my head this lot!

Good luck!

Mark.
Mark Boldry

Bob - it should be possible to modify the circuit to increase its sensitivity... the tacho is a simple monostable multivibrator as has been pointed out many times on this BBS.

Does anyone have a cct diag for the 'volts' driven (later) tacho? I have one only for the 'current' driven (earlier, wire loop) tacho.

It will be possible to run it off 5V. BTW - the orig device is made less sensitive than it might be because the 12v (white/black) 'switched' circuit would be very noisy, so would otherwise trigger the tacho monostable too often, and the gauge would always read max.

Find a cct diag, and I'll recommend a change.

(Emerald drives midget tacho no probs)

A
anthony

Ok Bill I'll do that - I can't find the diagram I was given but I can open up the ignition module later and sketch it out.
Bob T

Bob T I had seen a diagram of that somehwhere before but have failed to find it. As I am using the Wasted Spark coil pack, I would like to check out your diagram. I do know which 2 wires are the triggers.

Ant my tacho is the type with the 2 bullet connectors for the ignition circuit, I assume this is the current driven type also I would appreciate a summary of how to modify it please.
Bob England

Bob - the 'current' tach has a wire loop; the voltage type has a spade and IIRC another? type of connector?

I have cct diag for the current type I could send (actually from the web).

A
Anthony

OK thanks Ant my address is rjwelchmidgetATaol.com
Bob (robert) Midget Turbo

This thread was discussed between 08/05/2008 and 09/05/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.