Xu10J2Te And Tacho

[Wod 0]

Hi all, was looking for a bit of advice. I have taken on a 205 with conversion and just tidying bits up. Iv noticed the rev counter works but only at half the actual rpm of the engine? Does this mean the feed for the clocks is coming from a coil or something? Should it come from an ecu pin to the clocks?

Cheers

[Wod 0]

Could I connect a feed of the two coils via a diode and then into the clocks? Would that work?

[Henry Yorke 269 3 Cars]

 

You can modify the back of the tacho to get this to work as above (though I have not actually done this myself). It is the same mod that you do for a GTI6 conversion

[Wod 0]

Iv come across this before but everyone says its when there tacho isnt working? mines just reading half :-(

Cheers for reply

[Anthony 1,000]

Sounds to me like the conversion was either wired up wrongly in the first place (ie it's wired only to one side of the coil) or that a tacho adapter was fitted and one of the diodes has failed so you're only seeing the output from one side of the coil.

 

Unfortunately, you're going to have to have a poke around on the loom and see what's been done.

[Wod 0]

Wicked, il check this out then mate. If I want to take a feed from both coil negatives, can I take them off connected with diodes? And then straight into the clock?

Cheers bud

[welshpug 1,621]

Not quite, youll need a zener diode too, preferably a resistor to earth as well, simple enough to do and very cheap.

[Anthony 1,000]

You need to make something along these lines:

 

 

Simple to make and works fine, although personally I prefer doing it "properly" and using the clean tacho out signal on the ECU and modifying the 205 tacho to work with it.

[Wod 0]

You need to make something along these lines:

 

 

Simple to make and works fine, although personally I prefer doing it "properly" and using the clean tacho out signal on the ECU and modifying the 205 tacho to work with it.

Cheers man that looks dooable, the looms all sealed up so would be easier for me to do that for now. So I take it the above mod would work if the tacho gets its signal directly from the ecu? Would this just be a straight line from pin x straight into the tacho signal in or is there anything in between to account for?

Thanks for the help guys

[welshpug 1,621]

The signals would be the two coil triggers not the ecu tacho signal.

[Wod 0]

So are you saying there actually is no ecu tacho signal? Im asking if I could wire it up to the ecu and just mod the clocks as another option

[Anthony 1,000]

There's two ways of making the tacho work:

 

1. You combine the two outputs from the wasted spark coil using the simple diode circuit above and wire this straight to the existing 205 tacho wire without modifying the tacho
   
2. You wire the existing 205 tacho wire to the tacho out pin on the ECU and don't touch the coils, but you need to modify the 205 tacho PCB to remove/bypass part of the filter circuit so that it will work.

[Wod 0]

There's two ways of making the tacho work:

 

• You combine the two outputs from the wasted spark coil using the simple diode circuit above and wire this straight to the existing 205 tacho wire without modifying the tacho
• You wire the existing 205 tacho wire to the tacho out pin on the ECU and don't touch the coils, but you need to modify the 205 tacho PCB to remove/bypass part of the filter circuit so that it will work.

Thats it mate I was just double checking option 2 and making sure the line from the ecu is direct into the tacho Sounds easy enough! Thank you for the advise