ECU Speed Signal & Speedo Convertors

[Kevin]

Just as a matter of interest, does the speed signal that feeds the speedo clock come direct from the ECU?  Or does it recieve it separately from gearbox speed sensor, which is then fed to the ecu?

i.e. does it look go like:

Speed signal -> ECU -> Speedo

or

Speed signal -> Speedo -> ECU

or

Speed signal -> Speedo
                  ->ECU

The only reason I ask is if the speedo does take it\'s feed from the ecu then what stopping me from splicing in an electronic speedo convertor in the loom at the back of the ecu, instead of taking apart the dash to get at the back of the clocks?

[S3TH]

Getting to the back of the clocks is quite easy... :Giggle... it\'s the first panel that comes off when "taking apart the dash" so it\'s quite quick a pain free...

[Kevin]

That doesnt answer my question in the slightest, and are you telling me that:

Removing the side panel
Removing the lower panel
Removing the steering column cowl
Removing the clock surround
Unplugging the clocks and removing the instrument cluster......... without breaking any clips is easier than removing one plastic panel in the passenger footwell??? :rolleyes:

[S3TH]

I\'m saying it\'s unlikely you can splice an electronic speedo convertor into the ecu loom, if you could, something a versatile as an apexi could convert for you, I don\'t know maybe it can? ... Good luck

[RemarkLima]

I think the speedo has a seperate feed to the ECU. The reason I say this is my speedo registers as 0 on my apexi (I think the wire\'s been cut to the ECU to get around the 112mph limiter) while my speedo works perfectly.

HTH,
Mark

[DC-TYPER]

what wire do you cut at the ecu for this

[Kevin]

Which apexi unit are you talking about? PowerFC or RSM etc?  When I wired in my RSM a few weeks ago, that picks up the speed from the ecu (in km/h).

DC-TYPER:  To remove the speed limiter option, you need something like an RSM, where you cut the speed signal input wire, then that runs through the RSM then connects back into the ECU, thus removing the speed limiter.  Although I think if you just replace the standard ECU with say a PowerFC then that removes the speed limiter anyway.

Anyone else have any input on this matter?

[RemarkLima]

OK, my car (pre Apexi - which *does* remove the speed limiter) had a standard ECU (could have been opened up for all I know) with a Knighsports FCD Type D fitted (again, dunno how! Probably into the boost voltage I\'d imagine), but also had a black wire cut that went into the ECU.

It had bullet connectors fitted so obviously done so that it could be reconnected easily, but I pulled the error codes from the standard ECU and it had a speedo sensor error.

Then the Power FC reads 0kmph all the time... When I reconnect the wire I\'ll take a pic of what one it is as well.

Also never had any speed limiter problems at all.

[Kevin]

Does sound like the speed signal is split then and goes to the speedo and the ecu from 2 separate lines and not one connected one, as your dials would read 0 too.

[DC-TYPER]

i heard that you can cut a wire which delimits the car without buying the crappy converters(which i happen to have)

[RemarkLima]

It seems from my car that you can... However I have no idea what the wire is so will have to check it out next time I\'m under the dash

[Kevin]

i heard that you can cut a wire which delimits the car without buying the crappy converters(which i happen to have)

That\'ll be the speed signal wire that goes into the ecu then.  Dont know what effect it has on the rest of the system if you just cut the wire?  Maybe none, no harm in trying, but personally i\'d rather get a powerfc than start severing wires.

[RemarkLima]

Well it seem my car been running for the past year plus with no wire going to the ECU... I\'m sure there\'s a static (i.e not moving) switch / sensor however.

But it seems to have no major ill effects!