MR2 - S6 – single coil conversion

[TimTaylor]

Hey,
As my old ignition coil cracked, I’ve decided to get rid of the distributor as well and go for a coil on plug conversion with 1zz-fe coils. The Engine is running great with Ryan setting it up perfectly as usual

The only problem at the moment is that my tacho istn’ showing the rpms the engine is doing. Speedo is working fine.

So I read something about that common problem and noticed that I will have to replace the resistor in the tacho with a smaller one, or even completely remove it, which I already did.

The only Thing left to do is connecting the ECU to the tacho and most probably configure the ECU correctly. This is where I would need some help, I’m afraid.
I wanted to do the following:

1. Assign the output “Tacho” on the I/O configuration to a free pin (e.g. PWM08: CTL068 on my setup as shown on the screenshot that I took.

2. Connect this assigned pin of the ECU (PWM08 should be pin 16 on the ECU, right?) to the correct wire of my car (which I already found, the black one, pin 5 on the EA3 Connector in the engine room fuse box. I can take a picture if anybody else want to do this conversion and needs help in the future.)

The thing is, is my guess with choosing “Output Tacho” for the rpm signal correct? Or is it maybe "Engine Speed Controlled A" or maybe "B"?
And is the PWM-signal correct for the MR2 tacho? Or do I need an IGN or FUEL output, which I don’t think.

Thanks for any assistance
Robin

[Ryan.g]

Hi Robin,

Assign wire to the Tacho output in the Pin assignments on PWM8 if you have connected the Tacho wire to Pin16 on the S6gp.

Then you will need to Click Device - Program for this changes to be stored into ecu.

After this start the engine and see if the tacho is reading the correct RPM. If not adjust the Pulses per Rev under Output Functions - Tacho Output

You will need to Program the ecu again after making a change here

Ryan

[PQatPIT]

Might be that you need to remove some zener diodes from tacho pc board. Some versions of MR2 used coil negative wire suppressed by zeners to tacho signal. Oem wire from engine bay to instrument cluster is usable, but small jumper wire is necessary here.

[TimTaylor]

Great. Thank you both very much. That should help me getting to it

[TimTaylor]

Hey Everyone

could I use "FUEL 05 : CTL-070" which should be pin 69 as well to get a proper signal to my revmeter?

Or has it stricktly to be a PWM signal?

Thank you very much for your brilliant support. Can't wait for the Android version of the bluetooth module to be ready

[pat]

Tim,

FUEL5 will work just as well as any of the PWM outputs. They both switch to ground so their function will be identical for this application. PWM outputs cannot run engine synchronously though - so no injector drive or (when it happens) no GDI pump control. Other than that you can consider them the same as FUEL outputs.

Cheers,

Pat.

[TimTaylor]

Oh well, this Tacho thing is driving me crazy. I have no clue why it isn't reading anything.
I've connected pin 69 which should be Fuel5, right?
Pin69 leads straight into the Tacho Input (Pin3, plug B on the instrument cluster as shown below)

Simply spoken, I've put the Syvecs with pin 69 to where the Igniter was

I fully tested every plug (IE1 and EA3) and the whole connection from the ecu to the connector and there is no problem. Everywhere pass... no resistance, everything is fine. Except of the not working tacho.

When I turn on the car, the tacho reads zero. There is no reaction at all. I have tried three and six as output signal. I've selected fuel5 as tacho output. After both actions I pushed "program" to write it into the ECU.

I have also changed the 47k resistor in the tachometer to a simple wire...nothing
I have changed to a 10k resistor....nothing again

I took off the front glass of the combmeter and moved the needle under the stop so the needle hang down at about 6 o'clock position. When I turn on ignition, the needle moves to the desired start point at 0 rpm. When I fire up the engine nothing happens Neither with three nor with six selected on tacho output signal

Is there something I have overlooked?
Before the single coil conversion my tacho was completely spot on and I have done nothing harmful to it

[TimH]

I can't speak for this install, but many of the loom adapters I make need a pull-up resistor to +12V from the Syvecs output for the tacho drive. 1k is typical, but some need 100R. Worth a try?

[TimTaylor]

Well usually there is a 47k resistor in the tacho that needs to be replaced. Some say completely and some say, only change it to a 10k resistor. I've tried both with zero effect

Here is the picture of the resistor that needs to be replaced.


So you suggest to put in an additional 100R-1k resistor in the line from the Syvecs to the tacho, right? Just to confirm, as my English isn't that good.

[TimH]

I honestly don't know the details of your installation. Is that resistor a "series" resistor, or a "pullup" resistor?

The Syvecs output does not provide a 0-12V pulse. It is, instead, more like a relay with one contact connected to ground and the other open circuit.

If you connect a resistor from the Syvecs output "up" to a 12V source, then you will see a 12V pulse output. This is probably what the tacho needs to see.

The 47k resistor in the instrument cluster *may* be a "series" resistor that limits the current. It has a different function.

It will do no harm to try connecting a 1k resistor between the S6 output and 12V (leaving the connection between the S6 and the tacho as you already have).