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chownr

Definitive Aftermarket Tacho Convertor

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Cameron

OK, I just tried it out and modified the wiring to the tacho but it doesn't seem to work properly. I've disconnected the yellow wires and re-soldered them to pin 1 of the chip like in the photo. The wire passes through a hole in the board.

 

th_17062008471.jpg

 

When I started it up the tacho didn't work but when I blipped the throttle it moved, but didn't move to the correct RPM. If you increase revs the needle will move up but it will either move up too fast or will move up and then flick down to a lower RPM. Very strange. Can anyone suggest what's up with it?

 

I also changed my wiring so that pin 1 was +12v, pin 2 was -ve and pin 3 was the tacho signal.

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Miles

Is there a config in the ECU that sets the Rev counter, I know some use various signal and it sounds like your running half engine speed

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petert

I normally just jump the board as shown below, with no other mods. This works fine with a 12V square wave tacho output.

post-2864-1213866455_thumb.jpg

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Cameron

Hmm, I might give that a try. It behaves really strangely.. at constant revs the needle moves up steadily to 7K then flicks back down, keeps doing that. Something definitely isn't right. :lol:

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pug_ham

Looks a good route peter, easier than getting to pin one on the chip anyway.

 

Have you tried any on MP3.1?

 

Graham.

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petert

No, I haven't tried it on an MP3.1. It's an easy route though, as you don't even have to pull the needle off and unscrew the board. You can access the joint from the side, if you're careful. I did another last night and it works a treat. Although 205 tachos are very inaccurate anyway. For example:

actual RPM - indicated RPM

950 - 1100

1850 - 2000

7000 - 6800

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jackherer
Although 205 tachos are very inaccurate anyway. For example:

actual RPM - indicated RPM

950 - 1100

1850 - 2000

7000 - 6800

 

Based on limited testing I thought that was the case but recently I've been driving a 205 with a stack st400 alongside the standard tacho and they both agree with each other at either end of the ranges, I guess its just a one off as I have definitely seen a huge variation between standard tachos in the past.

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marksorrento205

Omex do something just for the 205 that wires from the output of the ecu (omex ecu Blue and yellow wire i think) into the 205 rev counter wire. Then 2 more wires that go to 12v and earth. Dont know how much it costs, they threw it in free with my order, so I guess not much. They reckon it solves the problem.

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Miles

The Omex is fine, I;ve done a couple of 600 series ECU with this mod and all is well.

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Cameron

Mine still doesn't work. :) I checked weather the tacho driver in the ECU can be re-configured but it can't.

Its still behaving very wierdly, slowly moves up the rev range then flicks back to 0 and repeats.

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welshpug

hmm, seems my pound's worth of resistors in a Film pot is looking to be far easier!

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maxi
OK, I just tried it out and modified the wiring to the tacho but it doesn't seem to work properly. I've disconnected the yellow wires and re-soldered them to pin 1 of the chip like in the photo. The wire passes through a hole in the board.

 

th_17062008471.jpg

 

When I started it up the tacho didn't work but when I blipped the throttle it moved, but didn't move to the correct RPM. If you increase revs the needle will move up but it will either move up too fast or will move up and then flick down to a lower RPM. Very strange. Can anyone suggest what's up with it?

 

I also changed my wiring so that pin 1 was +12v, pin 2 was -ve and pin 3 was the tacho signal.

 

 

To be honest, I think you have cooked the IC. The amount of heat generated from the soldering iron is transmitted straight up the leg of the chip and will cook it unless a suitable prevention method is used. Grab yourself another rev counter and do the conversion further back from the chip, I always solder to the leg of the last redundant component. Another sensible precaution is to hold the pin of the IC which is being soldered to with a pair of pliers, this will "soak" up the heat and prevent it cooking.

 

Maxi

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Cameron

Im not so sure.. You don't need to put loads of heat in to stick the wire onto the original solder and I'd have thought it takes a fair bit of prolonged heating to burn out the chip. Or are they pretty fragile?

I'll give it another go using my spare cluster and go from the resistor in the corner and see if it makes a difference.

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andychalmers

I need some help as im stuck even tho I've read every thread a dozen times. I have a S16 engine on throttle bodies & Omex 500 ECU. Im trying to get the rev counter to work, I car'nt use the ECU as the output is being used for the fuel pump (this ecu has 1 aux output which can only be used for 1 of the following:- 1)fuel pump 2) tacho 3) shift light)

How can I wire it without the ECU?

cheers

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pee vee

how have you got it wired at the moment? or how have you tried it?

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pug_ham

Just to update this topic, I finally got chance to test the modified pin 1 rev counter on TT205's car at Harewood last Sunday.

 

Pleased to say it works fine. (Thanks Dave).

 

Still I find it odd that they don't work on MP3.1 when the converted rev counters with new internals I've done work on both of these systems.

 

I've yet to test one on any other system although I think they work on Omex :) but should be able to confirm when Daz_C has tried the ones I left him on his car. ( I lent him one of each type, pin 1 modified & converted counter).

 

Graham.

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