205 Gti Rev Counter Isnt Working With Megajolt Though My 205 Euro Rall

[Grahamrally 0]

I've got a rally car which I'm running megajolt on to control the ignition system. We've done a complete custom wiring loom for a reshell in teh last 3 months. However my rev counter isnt working with the signals from either the Megajolt unit or the EDIS ignition module.

It did however work before with my previous dashboard, which was a 205 Euro rallye. We've checked that there is a 12v positive, an earth and a signal for the tacho, but the rev counter that's now in it, (UK spec 205 GTI), won't work with either signals. I have tried more than one to verify that it isn't just the rev counter that doesnt work.

Is there a specific range that the 205 gti rev counter works within??

 

Any help would be greatly appreciatd.

 

Thanks

Graham

[welshpug 1,626]

I think you need to make an adapter, have a look for a topic titled "aftermarket tachometers" (I think thats what it was called...)

 

myself and Spiky have made adapters to run Jetronic rev counters with motronic and magneti ecu's.

[Spiky 37]

yeah, just look in my profile for the posts i started

[MartinM 0]

However my rev counter isnt working with the signals from either the Megajolt unit or the EDIS ignition module.

 

Hi....so you've tried:

- MJLJ TACH OUT - pin 1?

- EDIS Clean Tach Out - pin 11? (if you can get to it!)

- EDIS PIP - pin 1 (or MJLJ pin 2)?

 

If none of those work, then you need to try the "diode" circuit from the coil -ve's

 

For all these, see http://www.autosportlabs.net/MJLJ_V3_vehic..._to_Tachometers

[Spiky 37]

if you want the diode loom version

 

i can sell you one £20 delivererd

[Grahamrally 0]

Martin, we've tried the MJLJ tach out - yes, edis clean tach out - yes, but not the PIP line yet! What I really want to know is if anyone knows if the rev counters from non gti's are very different to the GTI ones?

[petert 554]

It's a bit hit and miss I'm afraid, determined by the tolerancing in the tacho circuitry. Some work, some don't. Although the late model tachos seem to work without modification. You need to lower the resistance of the input resistor on the tacho circuit board.

[MartinM 0]

if you want the diode loom version

 

i can sell you one £20 delivererd

 

If you're talking about the 2x IN4004 and 1x 18v Zener diodes version from:

http://www.autosportlabs.net/MJLJ_V3_vehic..._kickback_pulse

...then as the total component cost is in in the order of 12p, I'd be happy to supply these in a loom version for rather less

[Spiky 37]

If you're talking about the 2x IN4004 and 1x 18v Zener diodes version from:

http://www.autosportlabs.net/MJLJ_V3_vehic..._kickback_pulse

...then as the total component cost is in in the order of 12p, I'd be happy to supply these in a loom version for rather less

 

 

 

nope as i use more components ......

 

 

 

thats my loom, and 20 quid is hardly breaking the bank and one less thing to worry about

[Grahamrally 0]

It looks like my friend has half solved the problem. We've skipped all the conditioning that the rev counter gives the input signal before reaching the microprocessor. It worked, just now need to calibrate it with the right resistor to give us the right amplitude.

 

If anyone is interested in finding out how we got the rev coutner to work with megajolt then I can post pictures after we've finished modifying it?

Graham

[ifcho 0]

Please post some pics

[MartinM 0]

Pics and a description would be very useful...

 

Regards

Martin

[Grahamrally 0]

Ok, I'll post some pics up when we've sorted out what we're doing with it.

 

Thanks,

Graham