rv8 speed transducer

[project 112]

i,am currently wiring up a 4L rover/TVR v8 in my mirage kit. having looked through various wiring diagrams etc there is a terminal on my ECU (14CUX) for a road speed transducer. could somebody explain what this actually does and more to the point will i have to fit one. To complicate matters a bit more i,am using a renault gearbox as opposed to the rover item, and a electric speedo instead of cable which i believe to rover transducer used, any help would be much appreciated thanks

[anonymous-user]

As far as I know it's used to control the idle air valve. Anything over a few mph and the ecu stops using the idle valve. Loads of rv8 kit cars don't bother with the speed sensor input and have no problems - maybe the idle valve just does nothing (i.e. closed all the time) without the speed input.
Mike

[project 112]

thanks for that,i,ll try the engine without the transducer and see what happens,a quick point though how does the ecu know that the car is moving if it is the job of the transducer to tell it to dispence with the idle valve? ie no transducer, no speed info to the ecu? anybody out there running a rv8i with any more info?

[blitzracing]

The transducer simply produces a 12 volt square wave at 4 pulses pre revolution of the speedo cable. It has two functions to stop the idle control when the car is moving, and to limit the top speed on the 4x4's so they dont crash, apart from when they are driven by women on mobile phones.....Leave it out and the idle can do some odd things.