Megasquirt To Tacho Signal

[pugpete1108 62 1 Cars]

i'm in need of help with the tacho wiring for my megasquirt set-up, i have lost count on how many threads i have read to try and clear it up so was hoping someone can give me a definite answer.

 

what would be the easiest and cheapest was of getting a signal from my ecu to my tacho?

im using ms1-e and phs 1 clocks if that helps.

 

i've seen wiring pictures about soldering difect from the ecu to pin 1 or something but dont really understand it

also something about using a resistor in line to change the signal? (sounds easiest option)

also changing the actual tacho itself for a later on? (what would be a suitable donor?)

[welshpug 1,622]

if its a digi signal akin to a later type Bosch Motronic or Magneti Marrelli as found on the 2.0 coilpack equipped engines then a pound's worth of resistors/diodes can make up a pickup you can place next to the ecu to translate the signal from the ECU to the coils, to an RPM signal for the tacho.

 

I'm not sure if you can make the Megasquirt ecu send a signal direct to the standard rev counter in then right "format"

[pugpete1108 62 1 Cars]

i might have to speak to megasuirt direct then and see if they can help me out.

anyway i got this far:

but how the hell do i get the orange plastic bit off without breaking it?

 

[pug_ham 240 3 Cars]

How have you got the black backing off?

 

With the two screws that hold the facia onto the rev counter body removed, pull the facia off the front & it'll take the needle off with it.

 

Graham.

[pugpete1108 62 1 Cars]

How have you got the black backing off?

 

With the two screws that hold the facia onto the rev counter body removed, pull the facia off the front & it'll take the needle off with it.

 

Graham.

 

the black backing just peeled off?

 

i have pulled on the needle but it was stiff and i didnt want to break it

[pug_ham 240 3 Cars]

Method as in my previous reply, thats worked on all the speedo's I've taken apart & the needle has never broken.

 

Graham.

[Mad Professor 7]

Good Day To You.

 

You say that you have MS1-Extra, do you know if that is using the version 2.2, 3.0, or 3.57 PCB.

Also do you know if the tach out mod has been added to your megasquirt unit, as if you brought it as a DIY kit this is not normaly encluded.

 

If you unit has been fitted with the Tacho out mod, you need to find out how it has been setup, and pulsed ground, 0-5v pulse or 0-12v pulse.

 

If you are using the standard 205 tacho, they work from a high voltage EMF spike when the HT coil fires. It has been covered before on the forum that you can bypass a resistor and diode to make it work with lower votages.

 

If you are running Wasted Spark via a coil pack you can used the 3 diode trick.

 

I hope this is of some help to you.

 

Just a question where did you get your MegaSquirt from?

Edited March 21, 2009 by Mad Professor

[pugpete1108 62 1 Cars]

Good Day To You.

 

You say that you have MS1-Extra, do you know if that is using the version 2.2, 3.0, or 3.57 PCB.

Also do you know if the tach out mod has been added to your megasquirt unit, as if you brought it as a DIY kit this is not normaly encluded.

 

If you unit has been fitted with the Tacho out mod, you need to find out how it has been setup, and pulsed ground, 0-5v pulse or 0-12v pulse.

 

If you are using the standard 205 tacho, they work from a high voltage EMF spike when the HT coil fires. It has been covered before on the forum that you can bypass a resistor and diode to make it work with lower votages.

 

If you are running Wasted Spark via a coil pack you can used the 3 diode trick.

 

I hope this is of some help to you.

 

Just a question where did you get your MegaSquirt from?

 

the unit is fitted with a tacho out but i am unsure what version pcb it is?

i am using the std 205 dash and running a wasted spark with coil pack so tha 3 diode trick looks good to me, how is it done?

it was built by extraefi so i will contact them to see how its been set up

[Mad Professor 7]

Ah extraefi, yer Phil Ringwood is a top guy.

 

As for the tacho 3 diode tick here you go:

[welshpug 1,622]

this is my effort, works fine

 

[pugpete1108 62 1 Cars]

mad- couldn't veiw the pic

and

welshpug- that looks pretty snazzy but where do all the wires go and where did you buy the parts?

[welshpug 1,622]

combination of Maplin and RS components, about a pounds worth of bits but some of the parts are only available in multiples (4 IIRC was the greatest number)

 

The red wires are the pickups which you hook up to each coil trigger, in this case it was an S16, I did one for my MP3.1 Motronic which only needed the 2 red wires as it ran a wasted spark.

 

Green is the earth, Blue is the wire that goes to wire 112 - Tacho

[pugpete1108 62 1 Cars]

combination of Maplin and RS components, about a pounds worth of bits but some of the parts are only available in multiples (4 IIRC was the greatest number)

 

The red wires are the pickups which you hook up to each coil trigger, in this case it was an S16, I did one for my MP3.1 Motronic which only needed the 2 red wires as it ran a wasted spark.

 

Green is the earth, Blue is the wire that goes to wire 112 - Tacho

 

ahh, i get it now, so you dont use the ms tacho output at all then.

i am running wasted spark so will just need two wires.

i dont suppose you could sort me out a component list (part numbers etc.) and maybe a wiring diagram?sorry to be cheeky.

 

btw how does the tacho read it?, like pulses per rev or what?

[welshpug 1,622]

not entirely certain of the actual signal, but one per spark, you don't use the Tacho output from the megasquirt, but you do go from the coil trigger wires on it (depends if you fire them directly or not)

 

IIRC PeterT posted up a diagram in a thread a while ago, I'll see if I can find it.

Edited March 22, 2009 by welshpug

[pugpete1108 62 1 Cars]

not entirely certain of the actual signal, but one per spark, you don't use the Tacho output from the megasquirt, but you do go from the coil trigger wires on it (depends if you fire them directly or not)

 

IIRC PeterT posted up a diagram in a thread a while ago, I'll see if I can find it.

 

yeah the coils are directly fired from the ecu so just the two signalwires from there then.

if you dont mind i would be very gratefull, i will try and have a look myself

pete