stand alone ECU but i want to keep my rev clock

[Nomuken]

In my case I have a 20V with coil on plugs, so no coil negative to get my tach signal. Haltech generates a tach signal nut my OEM rev counter doesn't understand it. So I still got no revs Any thoughts?

[Gnugfur]

Nomuken Wrote:In my case I have a 20V with coil on plugs, so no coil negative to get my tach signal. Haltech generates a tach signal nut my OEM rev counter doesn't understand it. So I still got no revs Any thoughts?

Now we're talking. And i understand your source of frustration.

Your problem is that the voltage your tacho is getting is wrong from what its expecting. What you need to do is find out the "spectre" it operates within and add resistorts until you're within that.

We had to to that on our turbolaurel.

[jondee86]

Nomuken Wrote:In my case I have a 20V with coil on plugs, so no coil negative to get
my tach signal. Haltech generates a tach signal nut my OEM rev counter
doesn't understand it. So I still got no revs Any thoughts?

Just going thru this exercise with my own ECU. It seems that when the
the factory tacho is driven from the ECU (as it is on the AE86), then the
signal from an aftermarket ECU may not be compatible for driving the
tacho... without some help.

EDIT: Above is not correct. After more research it becomes plain that
the ECU tacho connection is an input not an output. The tacho signal is
in fact generated by the igniter. And it will be a back EMF voltage spike
rather than a square wave.

In my case the tacho output is provided by a spare ignition output... this
is set up to pull 12V to ground. So the answer is to put put 12V onto the
line from the tacho to the ECU output by way of a 560 Ohm "pull-up"
resistor. When the ECU switches the 12V to ground, the result is a 12V
square wave on the tacho wire.

Haven't got it wired up yet, but if the original OEM ECU feed to the tacho
was a 12V square wave, then it should work fine

EDIT: Above solution is discarded, as a 12V square wave will not work
for the AE86 tacho. New solution is to use a small pullup coil instead of a
resistor, to generate a voltage spike. Wil post up the results after I get
back from vacation

Cheers... jondee86

[williep12]

jondee86 Wrote:

Nomuken Wrote:In my case I have a 20V with coil on plugs, so no coil negative to get
my tach signal. Haltech generates a tach signal nut my OEM rev counter
doesn't understand it. So I still got no revs Any thoughts?

Just going thru this exercise with my own ECU. It seems that when the
the factory tacho is driven from the ECU (as it is on the AE86), then the
signal from an aftermarket ECU may not be compatible for driving the
tacho... without some help.

EDIT: Above is not correct. After more research it becomes plain that
the ECU tacho connection is an input not an output. The tacho signal is
in fact generated by the igniter. And it will be a back EMF voltage spike
rather than a square wave.

In my case the tacho output is provided by a spare ignition output... this
is set up to pull 12V to ground. So the answer is to put put 12V onto the
line from the tacho to the ECU output by way of a 560 Ohm "pull-up"
resistor. When the ECU switches the 12V to ground, the result is a 12V
square wave on the tacho wire.

Haven't got it wired up yet, but if the original OEM ECU feed to the tacho
was a 12V square wave, then it should work fine

EDIT: Above solution is discarded, as a 12V square wave will not work
for the AE86 tacho. New solution is to use a small pullup coil instead of a
resistor, to generate a voltage spike. Wil post up the results after I get
back from vacation

Hi

Thanks for keeping me updated on this. I really hope it will work.


Cheers... jondee86

[assassin10000]

Anyone tried this?

http://www.toymods.org.au/forums/showthread.php?t=22574

Andrew

[Ivan141]

Ahaa, so that's the problem...
I have a spare rev clock and tons of the needed electronics lying around at home. I could make one of those signal boosters quite easily (would be nicer just to use a real coil instead of chopping up a relay, but this way you can fit everything inside a nice looking housing). Let me know if you're interested.

[Ivan141]

An interesting link: http://members.iinet.net.au/~awcabren/ae86gzetacho.pdf

[Ivan141]

It seems I'm the only one left who cares enough to continue on this subject, but then I ask myself: am I bothered?

I just couldn't withstand the allure of tinkering with some electronics and built myself a tach booster.

Here's the result:

http://www.xs4all.nl/~ivan141/pics/proje...oster2.mpg

Built using a brand spanking new small 12V relay, an overkill sized NPN transistor and 1 base resistor (like in the toymods link).

I feed it a 12V square wave generated by my megasquirt stimulator.. The clutter on my desk is mostly related to some other electronic tinkering I'm busy with at the moment. The booster itself is the wart sitting on that white breadboard in the middle. The black PCB is my arduino microcontroller, which has nothing at all to do with this, the green PCB on the left is obviously the stimulator board.

Hope you like it, as I said before, I can easily make these to fit the relay housing using proper small transistors, and have plenty of this stuff around, so if anyone is interested I can make them on demand.

Ican hear a slight buzzing in the cluster, so I still want to try cleaning the spikes up by passing the signal to the cluster through a 15v zener (effectively stopping any voltage lower than this from entering the cluster).[/img]

[Nomuken]

I also got a modded relay for my haltech from a guy on the german forum, cost me 30 bucks, but it works
Only downside ist that I get a 100-200 rpm with ignition on and engine not running

[irishtwincam]

Use these diodes on a twin coil pack setup and your stock AE86 tacho will work fine!
Big thanks to PhatBob for this info by way of the VEMS project.
Coil 1 and 2 refer to twincoil negative signal wires.