Rb25 Speed Sensor Ecu Wiring

[Franko07]

As stated I've realised that my gear box has no wiring what so ever on it and didn't really phase me as i don't care about reverse lights or speedo "cause race car" but found threads saying that the speed sensor wire needs to be hooked up otherwise the ecu tries to cut injectors or something thinking its in neutral?

Found the wire in the ecu my question is, can i run a wire straight from the gear box to the ecu and bypass the cluster all together as i don't care about this, but also which wire do you run as both are the same colour coming from the speed sensor? and only one ecu wire? I'm assuming one is an earth then?

Any one who does conversions shed some light as this is in a Cefiro and not much info on body looms...

thanks!

[89CAL]

I think it only drops the idle when the car shows speed of 0. Mine never used to have the input to the ECU from the speedo and i didnt even notice till i was looking at some of the ECU wiring one day and saw it had been cut

[Franko07]

Oh ok sure. Well the post that i was reading was for rb into s13 and they were saying its pretty important,apparently pulls power from your car and has a limiter cut and all that jazz. So i fogured it couldnt hurt to wire it up i just dont know how?

[89CAL]

Racecar but stock ECU?......

[Franko07]

yep, beginner race car

[Franko07]

will be going to a nistune later on

[GTSBoy]

No, cannot do what you want.

Gearbox output is AC sawtooth signal. Cluster converts that to 0-5V square wave that the ECU wants.

[Franko07]

ok sure thing that's ok as i have an r33 cluster in the car so it should convert it fine. What i really need to know is which wire is the signal wire coming from the sensor itself as they are the same colour??? and then i found this pic

http://s689.photobucket.com/user/rmcallis/media/Speedo%20Corrector/CopyofSpeedo-2RearShowingSignals.jpg.html

so once i find which is signal i can put it direct to the back of the cluster to that top left pin? and then run a wire from ECU to top right? then just power and earth and it should work?

Apparently FYI this really does effect the car, in the FSM it says that's it restricts your idle and has a fuel cut and stops your vct so its something you definitely want hooked up!!

Edited January 2, 2016 by Franko07

[Franko07]

cant find any more info in the fsm about it though just says you need consult to see if its working but she definitely isnt! lol

i took the sensor out of the box and connected a multi meter to both wires and put a drill on the end to spin it and i got a good voltage reading so i know the sensor definitely works as well still doesnt clear up which wire goes to the cluster

Edited January 2, 2016 by Franko07

[Franko07]

well from what i can work out apparently the voltage put out from the sender is in AC frequency so its basically un-polarized can any one confirm this? It explains why there the same colour cause it doesn't matter which way they go then so i might just twitch them together so i can swap them around in case it doesn't work...

[KiwiRS4T]

Does your car go? If so leave the speed sensor or you will be limited to 180 (bummer for a race car).

[Franko07]

yeh a lot of the posts are from people having problems trying to get around the speed limiter. I'm learning to drift atm so my entry speeds don't need to be as hectic for now. I guess ill hook it up and see if it makes a difference and if not i can always just unplug it again from the gearbox

[GTSBoy]

In my first reply I told you the sender outputs an AC voltage.

[Franko07]

yeah i didn't realise that meant they were un polarized, thanks!

[wildeagle44]

Slight hi-jack if i may but on topic.

How would one go wiring from the gearbox speed sensor to the ecu without using a cluster? Some sort of converter?

I dont have a cluster at all in the car. Was planning in racepak dash and wouldnt mind speedo to show.

[GTSBoy]

Just tuck a speedo head up somewhere in the back of the dash. You don't need the whole cluster.

Otherwise, yes, you would need to build a signal converter, and would need to probe the output from a real speedo head to see what the square waveform's characteristics were at different speeds. ie, you'd be interested to know if they ran a fixed frequency and varied the pulsewidth or if the pulsewidth remains fixed and they change the frequency (duty cycle) of the pulses.

[Franko07]

i read a lot of people were using something called a dakota box to do this, i didn't look into this much as i had a speedo I'm assuming its some type of signal converter though...

[GTSBoy]

I'd hate to think that it was actually "dakota box" and I would expect that it was actually "decoder box".

[wildeagle44]

Thanks for your help guys.

Quick search turned up dakota digital that make a speedo decoder box.

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/prd126.htm

[GTSBoy]

That device would need to be able to take in the AC signal and output the 0-5v square wave signal. This may or may not be within its capabilities, so best bet would be to ask them. Many such electronic boxes (like the Jaycar kit) will only pass out the same type of signal that was passed in - just sped up or slowed down.