Stock AE86 Rev counter

[Will]

Has any one got the Vems rev output working with the stock Rev counter?
If so where can I find the wire I need to connect to the dash on the AE86 loom?
Had a good look about on the various AE86 sites but can't find much info.

Thanks

[rob@vems.co.uk]

try taking a wire with a 12v feed and a 300R to  1K resistor, and the AE86 revcounter wire and bang them off each other to see if you get any movement on the rpm - the quicker you make and break the connection the more the RPM needle should move.

If theres no movement its because the tacho needs more of a voltage kick, and we'll need to work that out when you've done the 12v test.

It might be worth using your diode pair connected to coil 3&4's ground wires. like you did with the coilpack from before...

Rob

[Will]

I never got round to doing that Diode method as I don't know where the wire in the loom (car side etc) is for the speedo. I know its meant to be down the left hand side passenger foot well area where that relay board is, other than that no idea really?

[rob@vems.co.uk]

Well eitherway you're going to need to find it for this one

Rob

[irishtwincam]

Black with orange stripes, coming out of plugs by the stock ecu.
If its an early model, its on the bulkhead connector that splits in two behind the intake/engine.
Same colour scheme.

[Denmark]

Yep ,its indeed the black with orangestribe,
On mine i found the wire in the bulkhead plug,
but i never got it working great,
Mine would work fine up to around 4krpm, and it would then just fall to zero again,
That could probbely had been fixed pretty easy, but i never got around to do it.

It did not bother me much ,as after 4krpm i better hold on to the steering wheel, when it broke traction, pretty easyly 

http://www.vems.hu/wiki/index.php?page=MembersPage%2FSkassa


/Skassa

[Will]

Did you use any pullup resistors or just straight from vems to the black/orange wire?

[rob@vems.co.uk]

VEMS doesnt kick out a voltage, so the pull-up will be needed - if its enough of a voltage, personally I think its worth driving the tacho from the negative wire on one of your coils.

[Will]

Will give that a try then, atleast I think I have the right dash wire.

[Will]

The diode method doesn't work, but 12v direct on wire works, so how do I do the pull up resistor or do i just connect 12v the taco/ecu wire?

[gunni]

12v - resistor - tacho wire.

[Will]

12v - resistor - tacho wire.

Where does the ECu wire go in that lot? Before the 12v wire?

[rob@vems.co.uk]

Tacho wire to the ECU.  12V via the Resistor to the Tacho wire to "pull" the tacho voltage up towards 12v.

When the ECU's tacho channel is closed the tacho sees 12V, when the ECU opens the channel the current flows to ground and the tacho sees 0V.

[Will]

Ok thanks, is there a rule of thumb of what resistor to use? Or just try one? Like 330Ohm

[Will]

Can I share the 12v that goes to the relays turning the ECU on and off, or will the tacho wire from the ECU make the power relays turn off?