Rpm Signal Off Crank Angle Sensor

[RB20DET_Silvia]

Hey guys,

How can i get a RPM signal from my crank angle sensor i got a RB20DET in a Silvia....and im getting a faulty reading from ECU pin out point.

I want to hock up a tacho guage.

- Luke

[RB30-POWER]

I don't think you can, as the CAS is just ref/sync pulses for the ecu to decode for crank position and RPM.

I don't see how the ecu tacho out pin function could be faulty myself.

However if you want to make an alternate output, because its a multicoil motor, you have to use a circuit like this.

http://www.gweeds.net/carpage2/RevCounterCircuit.pdf

Hope that helps.

Edited January 14, 2006 by RB30-POWER

[RB20DET_Silvia]

thx mate,

But i have heard from alot u can do it from crank angle sensor since its picking up a rev signal....and u can have fauty output signal from ecu...very easy.

- Luke

[RB20DET_Silvia]

- bump

[browny]

Hey guys,

....and im getting a faulty reading from ECU pin out point.

- Luke

<{POST_SNAPBACK}>

What signal are you getting and how do you know it's faulty?

[RB20DET_Silvia]

im getting it reading at 3000 rpm for a couple secound and i leave it there and it does not respond after that.....hence its faulty output.

- Luke

[browny]

How is it all connected?

The tacho pin at the ECU does not output a signal as such. It only switches the circuit to ground so as to produce the square wave. Unless the pin is also provided with a voltage source from somewhere (the OEM R32 tacho provides 5V internally) then you won't generate any signal. Well, I guess technically you do generate a signal, but a 0V-0V square wave isn't exactly useful.

Edited January 17, 2006 by browny

[RB30-POWER]

What value pull-up resistor are you using? Or it internal in the cluster itself?

[66 skyline gt]

from memory i had to do this on my gt with the rb conversion, you need a 1k resistor and need to join it from taco signal on ecu to one of the earth wires that feed into ecu. this acts as resistor acts as a coil. then ya fit your taco feed wire from the esrtor side closest to the rpm signal of theecu and presto, an taco that works. jsut pm mme for more info

[66 skyline gt]

change that it was an ignition feed to ecu not an earth feed

Edited January 17, 2006 by 66 skyline gt

[RB30-POWER]

yeah, you attach the resistor across the tach signal output to +12V, but this is only ok if the guage uses 12V square wave. If it uses a 5V or 8V square wave your stuffed i think.

[browny]

If the pull up resistor doesn't work then you can get devices that will produce the correct signal for your tacho. Pull up resistor = 20c fix. Otherwise $50-100 for a booster.

Depends what the tacho is designed for as to what it'll need. Most aftermarket stuff is either 12V, high voltage (for coil type ignition) or multi use. OEM stuff, well that varies.