The Dispatch | Expert | Scudo Hub

RegW

Member

From: Bristol

Registered: 2024-04-21

Posts: 347

tacho

I've been looking into building a tacho for the van and found I can tap into the engine speed signals
to the ECU off the OBD port
It's 14v square wave which I'll use an opto isolator on to drop it to a 5v square wave and and Arduino Nano
to convert and output this to either a display or a cheap 52mm tacho ofn that Ebay

I did a quick test using a scope and got 27hz frequency at roughly 800 rpm
an engine turning @ 800rpm spins 13.333 times second so it seems to be pulsing roughly at a 2 to 1 ratio
so I'll start with that as a ballpark and refine it later.

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When all else fails, RTFM  - 2006 Expert 2.0 HDI/110

kenbw2

Administrator

From: Preston

Registered: 2017-11-26

Posts: 1,612

Re: tacho

Wait you can get a revs signal from it? How are you getting that?

Oh, OBD. That's me out. Dammit

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2000 Citroen Dispatch 1.9TD XUD9 Camper Conversion
1999 Citroen Dispatch 1.9D DW8 Disassembled Camper Conversion
1996 Peugeot 806 1.9TD XUD9 Spare vehicle
1998 Citroen Synergie 1.9TD XUD9 Snapped timing belt

RegW

Member

From: Bristol

Registered: 2024-04-21

Posts: 347

Re: tacho

the xud9 was used various vehicles like Citroen BX of that era plus the late 90's Xantia 1.9TD so you may well have a crankshaft position sensor option.
Check this out as the look up the table mentions xud motors, you never know.

https://www.ebay.co.uk/itm/317724829607?

Last edited by RegW (2026-04-08 12:39:47)

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When all else fails, RTFM  - 2006 Expert 2.0 HDI/110

kenbw2

Administrator

From: Preston

Registered: 2017-11-26

Posts: 1,612

Re: tacho

Yea My synergie had a rev meter. I tried swapping out the binnacle to see if it worked on mine but no dice

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2000 Citroen Dispatch 1.9TD XUD9 Camper Conversion
1999 Citroen Dispatch 1.9D DW8 Disassembled Camper Conversion
1996 Peugeot 806 1.9TD XUD9 Spare vehicle
1998 Citroen Synergie 1.9TD XUD9 Snapped timing belt

RegW

Member

From: Bristol

Registered: 2024-04-21

Posts: 347

Re: tacho

I would guess that was because they didn't bother to fit a crank sensor in the vans engine in the factory
as the van had no tacho so the synergie binnacle didn't get any pulses.

This may help to decide if you have one

"The crank position sens"or for the XUD9 engine is typically located on the top of the bell housing, above the flywheel. It may be hidden by the thermostat housing on some engine"

If you have or get one this gives you options

Last edited by RegW (2026-04-09 15:44:18)

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When all else fails, RTFM  - 2006 Expert 2.0 HDI/110

RegW

Member

From: Bristol

Registered: 2024-04-21

Posts: 347

Re: tacho

Arduino? we don need no stinkin Arduino's
I bought a cheap wee tacho ofn that Ebay (£7.99) and it runs directly off the OBD port
No signal processing needed Woo Hoo!
The white back light may be bit harsh at night but I have few cunning plans to deal with this
if it is.

Last edited by RegW (2026-04-10 17:08:21)

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When all else fails, RTFM  - 2006 Expert 2.0 HDI/110

RegW

Member

From: Bristol

Registered: 2024-04-21

Posts: 347

Re: tacho

in, working and more or less tallies with Torque pro

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When all else fails, RTFM  - 2006 Expert 2.0 HDI/110