ecu speed sensor

[tommmtom]

hi guys!
can anyone give me any info on the speed sensor that goes to the ecu from the speedo. I don't have a speedometer so don't have the speed sensor for the ecu. I need to have one now to get speed readings through my ecuTalk so hoping to fix something up. At the moment i have a reed switch that is triggered every time the speedo gear in the gbox turns. is this how the speed sensor works? if so i can just feed my reed switch signal into the ecu!
cheers guys

 

[tommmtom]

Anyone? Just need to know what form of input the ecu is looking for

 

[Enuo]

The ecu doesn't need a speed signal to work. Disconnected mine. You need to work out the hz/speed ratio before you can do anything with the signal.

 

[l_jonez]

Not sure but would it not be simpler to fit a electronic speed sensor?

 

[tommmtom]

I don't have it connected now and it all runs well. Speedo cable is going into a homemade thing that earth's every rotation of the cable for the electronic speedo I'm using to detect speed and works fine. But now I've got an ecuTalk lcd display on the way and that works out speed, distance and MPG from the ecu speed sensor input! So need to figure out what if the ecu is looking for a voltage from a hall sensor or something, or simply a magbetic switch sorta thing (like bicycle speedo pickus)

 

[Enuo]

I think its resistance it measures (probably to earth) through a sensor on the back of the clocks that varies as the needle moves? Input comes from the dash clocks at any rate, and I don't think it is accurate in the slightest.

 

[micramarch]

Here is a thought. Why don't you remove your manual speedo drive in the gearbox and install an electronic speedo gear in the gearbox and hook up the wires. This will give you a signal for your ECU Talk.

 

[Enuo]

if its manual drive loom there will be no plug for it so ecu won't register the signal.

 

[SirChris]

if its manual drive loom there will be no plug for it so ecu won't register the signal.

So only specific ECUs do wire speed?

 

[Enuo]

tbh, I don't really think any of em do... maybe the motronics? Only speedo input on the mechanical speedo cars is a single wire to ecu, but dunno what it reads. Could be a pulsed signal like the electric sender unit on later gb's I guess, but not got anything to hand to measure and drive at the same time. Ed would know.

 

[frank]

its a reed switch at the back of the speedo head according to the pdf manual

 

[Enuo]

pulsed output then... guess it does read speed Or at least makes decisions based on certain speed criteria. It may only be able to tell basic things, like x<V or x>V

 

[frank]

it uses the speed sensor and neutral switch for radfan, aircon and idle control apparently

 

[Enuo]

Could still be hard wired control rather than logic control, in which case you might not have a useable number to pull off the consult.

 

[frank]

on page 17 andy https://www.dropbox.com/sh/lsp2a1h129ymgfu/AAA8kWVCSYdf7nag5GsDScdga/FUEL & EMISSION CONTROL-1.pdf

 

[frank]

and p 24 " if the vehicle speed is over 50mph = radfan off

 

[davyboy]

Like all things female.....complicated !

 

[SuperUno]

Clever! You learn something new everyday!

 

[frank]

Could still be hard wired control rather than logic control, in which case you might not have a useable number to pull off the consult.

i just tested it on consult/ecutalk software andy, and you get an accurate and progressive speed readout (albeit in km)