MR2 - S6 – single coil conversion

[TimTaylor]

Yes, the 47k resistor is a series resistor that limits the current.

I'm not quite sure, I have fully understood you. You mean I should leave the S6 - tacho connection as it is now and I shall add a pull-up resistor in the 12V feed-line leading to the tacho from the car. So not putting the pull up in the S6 - tacho line, right?

This could be difficult as the tacho gets it's 12 V together with several other things like water temp gauge, oil pressure warning light etc.

here you can see the full installation... perhaps you can show me where I have to put the pull up to?

[TimH]

Connect a resistor from the S6 output up to a 12V feed.

This is a plundered image, but think of the "hardware switch" as being the S6, and the "controller input" as your instruments. Ignore the voltages etc!

[TimTaylor]

ah ok, I think now I have got it.

I connect 12v into my existing S6-tacho line with a 1k resistor in? So that the 12V-pullup line and the S6-output both go together into the tacho?

so it is the green line you want me to add?

[TimH]

Yep

[TimTaylor]

Ok, thanks. I can try this. As long as you are completely sure it does no harm to anything.

The thing I am wondering is, how this is supposed to work as the S6 pulls to Ground at fuel outputs and this is, according to the wiring diagram, exactly what my tacho needs.
Wiring in a pull-up with +12V should get things mixed up, or am I wrongly thinking?


And another important question on my way solving that issue: I have connected the tacho drive via the Fuel5-pin69. Is it possible, that I choose the "output testing" menu and use "fuel pulse request" on number 5? What kind of fuel pulse duration do you suggest in this case?
Should be much easier to test it this way, than firing up the engine all the time for a few seconds.

[TimH]

As I said, I don't know your installation details or the car, but any tacho will need a signal that swings between 0V and 12V. Since the S6 only provides a grounding contact, something, somewhere, must provide the pull-up to 12V.

If your tacho already does this, then the resistor I've suggested is not necessary.

Will it do any harm? No.

My recollection of the output testing is that it will only send a single pulse, not repetitive pulses, so I don't think it will help.

[Heinz]

Hi,
i have done a lot of Toyota MR 2 and Celica conversions from single coil to coil on plug or wasted spark Coil packs.
Most of the older Toyota Rev Counters are Coil negative Rev Counters which may not work with the above connetions because they need a voltage spike rather then a ground signal. My solution is the following circuit, which generates a voltage spike and works in most cases.
If it still does not work some Rev Counter may need a 220Ohm 5Watt Resistor instead.

Drehzahlmesser Tacho Signalconverter VW - Toyota - 1.jpg (18.5 KiB) Viewed 55544 times

Heinz

Luepertz Motorsport
Syvecs Dealer Germany
http://www.Luepertz-Motosport.de

[shmed]

Sorry for the thread-jack, but this is exactly the issue I have found on my MR2 with a Syvecs ECU.

I seem to have a resistor between pins 21 and 14 (PWM-6) and then the output goes off to my Tacho (this is the pull up part from what I understand as pin 21 is 12v Live). The tacho stopped working, but I think I know why, but to fix it I have a few questions:

1. Where can I buy the crimps for the Saab loom connector (the female one that fits into pin 21)?
2. I have a data logger that is expecting a square wave digital input for RPM. Can I use the tacho output to drive both the 12v tacho, and also feed the data logger?
3. If the answer to 2 is no, then can I output the tacho data on two separate outputs from the Syvecs?

[TimTaylor]

Hey,

thank you all!!!!
I now put in a circuit Heinz suggested and I now have close to 4000rpm in idle but at least I have some reaction and I am pretty sure, the rest can be sorted out with adjusting the signal pulses coming from the S6

cheers to you all


and toshmed... unfortunately I don't know the answer to 1 but I guess you could solve 2 with just making a Y-connection. As far as I know you can only assign one pin to the tacho output.