Tachometer With Aftermarket Ecu

[welshpug 1,657]

Larson do you know what wattage R1 is?

 

you were right on the price, I think I can make 5 of these for £5.41! (RS has a minimum order of 5 )

 

just need to figure out how to package it...

Edited August 4, 2007 by welshpug

[Emyr 0]

Order list for RS Components (www.rswww.com)

 

Item: Diode,Rectifier,1N4004 (RoHS)

RS Stock No: 348-5369

Price: £0.06

 

Item: Diode,Zener,SMT,SML4744 (non-RoHS)

RS Stock No: 215-7372

Price: £0.452 each (multiples of 5 only)

 

Item: Resistor,wirewound,silicone coated,2.5W,1k (RoHS)

RS Stock No: 199-7135

Price: £0.43 each (multiples of 5 only)

 

Total for 5 circuits: £5.01 + VAT

Edited August 4, 2007 by Emyr

[Guest larson]

excellent, thank you very much!

 

is there a way of converting the signal from the ECU to what the jetronic tacho requires instead of adding more wires to the engine bay though?

 

I guess it would only be 3 short wires if I mount this on the ECU box, just use wire 112 and cut the ecu signal wire.

 

Well, it's an option. It's up to you to decide what method suits you most

Since I was making all new ECU and engine wiring harness it was not a problem adding two more wires with two pin connector to it.

I have also left tacho input wire from ECU (5V) untouched just in case I will need to change tachometer, sold ECU or install ECU into onother car.

So now tacho adapter is removable device and I have two options for tacho input.

 

Larson do you know what wattage R1 is?

 

you were right on the price, I think I can make 5 of these for £5.41! (RS has a minimum order of 5 )

 

just need to figure out how to package it...

 

Don't know what wattage, sorry. Picked the first available one.

Edited August 4, 2007 by larson

[pug_ham 244 3 Cars]

is there a way of converting the signal from the ECU to what the jetronic tacho requires instead of adding more wires to the engine bay though?

Yes, but not sure what it is exactly though but afaik its by tapping into one of the wires on the e coilpack plug.

 

I'll try to ask Dave at Harewood tomorrow if he knows / can remember because he mentioned it to me after seeing Wayne at chipwizards do it breifly on his car.

 

Graham.

[Richie-Van-GTi 71 2 Cars]

it should be a case of tapping into the coil trigger wire(s), if there is more than one such as a wasted spark set up then you need diodes and rectifiers to stop feedback and to smooth the signal.Ive just done mine with a wasted spark set up.

[welshpug 1,657]

it should be a case of tapping into the coil trigger wire(s), if there is more than one such as a wasted spark set up then you need diodes and rectifiers to stop feedback and to smooth the signal.Ive just done mine with a wasted spark set up.

 

thats exactly as detailed in the previous posts, my point was to be able to use the signal from the ECU directly.

[petert 586]

thats exactly as detailed in the previous posts, my point was to be able to use the signal from the ECU directly.

 

That's why I suggested to try a pull up resistor as well. If the ECU output is grounding, you need to hold the input high to create the necessary square wave.

Edited August 6, 2007 by petert

[pug_ham 244 3 Cars]

To use the ecu feed you need a suitable rev counter or some way to convert a digital signal to an analogue one to work on the standard rev counter (diodes as posted before).

 

Graham.

[welshpug 1,657]

hmm, I've either fried one of these diodes, or this wont work on my setup

 

hooked a feed to pins one and 2 of the ecu (wire to ignition amp) these go through a pair of resistors then through a zener diode to the tacho wire and off to earth as well (before the zener diode)

 

basically exactly as described earlier

[Guest larson]

hmm, I've either fried one of these diodes, or this wont work on my setup

 

hooked a feed to pins one and 2 of the ecu (wire to ignition amp) these go through a pair of resistors then through a zener diode to the tacho wire and off to earth as well (before the zener diode)

 

basically exactly as described earlier

 

 

If you are talking about adapter from -ve side of the coils then your description is not right.

 

 

So your ECU controls Ignition amp and not coilpack directly using high ignition coil drivers?

Do you have 2 ignition outputs from ECU?

 

Is ignition signal from ECU to Ignition amp logic level in your case?

You should take -ve from your coils then (wires between Ignition amp and coil): -ve from coil for 1&4 cylinders and -ve from coil for 2&3 cylinders and connect these wires to diodes, not resistors, you ground through resistor...

Edited August 8, 2007 by larson

[welshpug 1,657]

i'm taking the feed directly from the ECU plug, is this not correct?

 

I think the main problems arose from the zener diode supplied by my brother :/

 

I have got a diode thats easier to use and will have another go

[welshpug 1,657]

this is what I have made-

 

 

but it doesnt work, I am attaching the 2 red wires to pins 1 and 2 of the ecu, the black to the tacho feed and blue to earth.

[Mikey G 3]

Welshpug, i recently did this for someone with a 2 litre turbo conversion, the 2 outputs on the ECU are just for the ignition amp to trigger, which grounds out the earths from the coils to make a circuit. You need to connect the 2 wires of the unit you have made to the actual negative wires from the coils.

 

I didnt make a fancy board, i just soldered and insulated all 4 components together, heat shrinked them so 3 wires came out one end and the single tacho wire came out the other. I connected the 3 wires direct to the wires near the ignition module using the earth for the module itself. Connected the resultant output direct to the cars tacho wire and it works a treat.

[welshpug 1,657]

excellent thanks Mikey, I was going to try it on that side of the amp in the morning.

 

off topic but whereabouts in Gwent are you?

[welshpug 1,657]

right, as suggested I took the trigger from the wires amp-coil, and used the amp's earth wire.

 

works just fine,. the only query is; does the wattage of the zener diode affect anythuing? as the needle seems rather slow to react.

 

in the picture above, the order left to right is; D1 D2 ZD1 and R1

 

specifications of which are as close as possible to the haltech diagram

 

D1+2, Rectifier diode 1N4004 1A 400V

 

ZD1, BZV85C 15V 1.3W

 

R1, ER74 1K 2.5W

Edited August 9, 2007 by welshpug

[Mikey G 3]

Meirion, i managed to get hold of the 1N4744 zener diode for the car i did, but i also used a 1K 1W resistor not a 2.5W resistor. Not sure how much of a difference it makes though. Some people have said you dont need the zener so if you try bypassing that first see if it makes a difference to the revcounter? If so you know its the zener, if not then you could try a different resistor maybe?

[Discostu 6]

Mikey G did my tacho and i can confirm it works a treat, and looks tidy to

 

And to answer u'r other question (i'm sure he wont mind) he can be found in the Newport area of gwent.

[welshpug 1,657]

Meirion, i managed to get hold of the 1N4744 zener diode for the car i did, but i also used a 1K 1W resistor not a 2.5W resistor. Not sure how much of a difference it makes though. Some people have said you dont need the zener so if you try bypassing that first see if it makes a difference to the revcounter? If so you know its the zener, if not then you could try a different resistor maybe?

 

 

thanks, some more to have a go at, as soon as I source another inj relay...

[Hilgie 16 2 Cars]

I don't use the Zener at all..works like a charm

[Gibbo GTI 0]

Welshpug, i recently did this for someone with a 2 litre turbo conversion, the 2 outputs on the ECU are just for the ignition amp to trigger, which grounds out the earths from the coils to make a circuit. You need to connect the 2 wires of the unit you have made to the actual negative wires from the coils.

 

I didnt make a fancy board, i just soldered and insulated all 4 components together, heat shrinked them so 3 wires came out one end and the single tacho wire came out the other. I connected the 3 wires direct to the wires near the ignition module using the earth for the module itself. Connected the resultant output direct to the cars tacho wire and it works a treat.

 

 

Which ignition module 'pins' did you connect the 3 wires too? Am in the process of fitting a 2l mi16 with motronic mp3.2 to my 205 and will need to do this.

[welshpug 1,657]

dont know which pins, just whichever wires go to the coils from the amps, you may need 4 wires through rectifiers instead of the 2 as pictured as you have 2 Amps, depends how many wires go to the coils from the AMPs.

[Mikey G 3]

Just had a quick look at a diagram, terminal's 1 + 6 should be the wires between the coils and ignition amp, 2 +7 go from the ignition amp to the ecu, dont use these. Terminal 4 should be the earth for the ignition amp. So the diodes go to terminals 1 + 6 and the earth to 4. the other 2 wires should be noticably thinner and they go to the ecu. And the final connection will be direct to your revcounter.

 

EDIT, as you look at the amp i think the terminals go left to right but it is marked on them anyway. If it is a 4 coil setup it will have 2 ignition amps but the wiring should be the same just need to double the diodes and do both modules.

Edited August 13, 2007 by Mikey G

[pug_ham 244 3 Cars]

as you look at the amp i think the terminals go left to right but it is marked on them anyway. If it is a 4 coil setup it will have 2 ignition amps but the wiring should be the same just need to double the diodes and do both modules.

 

This is the order of the ignition amp plug pins on the jetronic loom if its any help;

• Pin 1; coil plug pin 2.
  
• pin 2; Earth to pin 3 on smaller brown plug under dash.
  
• Pin 3; dizzy field plug pin 1
  
• Pin4; Coil plug pin 3
  
• Pin 5; dizzy field plug pin 3.
  
• Pin 6; dizzy field plug pin 2.
  

Graham.

[Gibbo GTI 0]

I found this pic of the ignition module for the 2.0 mi16

[Mikey G 3]

I found this pic of the ignition module for the 2.0 mi16

 

Cant work that one out, too many wires and only one coil. What does B stand for?