Ignitor circuit details needed.

[misterforager]

Hello,

Can anybody tell me where I can find the internal circuit diagram for a 4AGE coil ignitor? The coil/ignitor is from a 1985 UK spec AE86 and is fitted to my Triumph Spitfire project (4AGE engine/T50 box). I hasten to add that I did not break an AE86 for this! The engine and box were imported from Japan many, many years ago and the the rest of the parts from a written off rally car.
The reason I need the schematic is that the car has a pseudo-classic electronic tachometer (CAi gauges) and does not work using the ignitor's raw tacho output. The ignitor tacho output signal is derived from the IGT pulses (from the ECU), but is not simply a direct connection to the coil -ve terminal. A temporary connection to an old O/E AE86 tacho works - so the ignitor is ok. Part numbers on ignitor are:-

ND part number 131100-3701
Toyota part no. 89620-12270

Please does anyone have a schematic for this ignitor - or can somebody pull apart a broken/faulty one and work out the circuitry from that? Maybe someone out there can sell me a faulty/scrap ignitor of the same type? Is there a website that has archived N-D diagrams? Would be useful to know the ECU internals too, in case of future faults and repair.

As for the tacho problem, I have electronics skills, so feel free to chat technical stuff e.g. is the signal source open-collector/drain etc. I have looked at the excellent info at this link...

http://www.autoshop101.com/forms/h39.pdf

...but it only briefly mentions the ignitor's tachometer signal (no detail).

Another way to solve the problem might be to analyse the Denso tachometer. The type fitted to the AE86 has a 30K resistor feeding the IG-signal (tacho output from ignitor) into a chip with device number T2685A. I have trawled the internet and cannot find a datasheet for this IC. If I had a schematic for the AE86 rev counter, I could work out what the electronics does with the IG- signal and put together a simple interface to my aftermarket rev counter. Please note once again that IG- (as labelled on the back of the AE86 instrument pod PCB) should not be confused with the coil -ve terminal, they are different signals.


Also, note that I don't need external wiring diagrams - got all that stuff!

Thanks to you all for any help you can offer.

[irishtwincam]

On toyotas, especially single coil toyotas as new as 95, the tacho signal is literally just the coil - pulse.
On wasted spark setups on a toyota, the igniter basically has diodes to join the coil negatives and drive the tacho.

On an AE86, the tacho is connected directly to the coil negative terminal.
Same on AW11 and AE82, and AE92 and as I pointed out, every other toyota with a single coil for the longest time!


IGf and coil negative are filtered differently AFAIK.

[misterforager]

Thanks, but I beg to differ on slightly on that. A multimeter between the ignitor tacho output (IG-) and the coil negative terminal shows approx 1K of resistance. However, that does not necessarily mean simply a single resistor between thos terminals - it could be any form of transistor/diode/resistor network that's inside the ignitor. I believe that IG- is a 'cleaned up' version of the coil -ve. It's probably switching betwen 0 and IG+ colts i.e. a nice digital waveform with all the coil -ve spikes removed. I just need to know exactly what's inside the box to generate IG-! I'll put a scope on the IG- signal tomorrow and see what it looks like - with or without a tacho connected.

[misterforager]

I put a scope on the tacho signal both with and without the Denso O/E rev counter connected. The scope traces showed a 0 to IG+ waveform including substantial spikes. That info, in conjunction witht the measured 1K resistance between IG- and the coil -ve terminal leads me to conclude that the internals are as shown in attachment.

.[img name=]http://www.aeu86.org/files/ig/ignitor_tacho_signal_264.zip[/img]

The good news (for me) is that my CAi rev counter works fine if I use the available option of a 'coil -ve' connection (as opposed to an 'ECU signal' connection). It obviously didn't like seeing a spiky coil -ve type signal at it's 'ECU' input - probably expecting a clean 0 to 5v digital waveform? The fact that there's a 1K resistance in series makes no odds.

Please not that my result is only valid for a UK setup with the parts numbers mentioned at the start of this thread.