Help needed with inductance type crank angle sensor.

[smash250]

Hi all, im new to this forum and hope someone on here can help me out. Im a sparky by trade however although i play with electricity everyday i am not very familiar with electronics.
Here is my problem/situation: I have recently done an engine conversion on my GU Nissan patrol. The patrol came from factory with an ecu controlled 3L turbo diesel. I have removed this engine and replaced it with a Non-ecu controlled 4.2L turbo diesel. Now i have re-wired the engine to run however i am having trouble getting the Tachometer to work properly. I have installed an induction type crank angle sensor- which picks up off the timing gear teeth and sends an AC pulse signal to the (Original ECM) now the tacho works but is not calibrated as the pulse signal is different to the original motor...i.e different number of teeth on the pick up. I brought home a digital optic RPM meter today and set it up on the crank to get a TRUE reading of RPM. I got a reading of 645RPM @ idle on the meter. The tacho on my dash board read approx 380RPM. Now please somebody tell me if im wrong in thinking this but, is there some sort of multiplier device i can wiring in between the sensor and the ECM so i can vary the pulse to be able to Calibrate the pulse frequency so to show the correct RPM on my dash?

Cheers Ash

 

[MikeMl]

Read this thread.

Count the number of teeth on the new flywheel, call it n. Count the number of teeth on the old flywheel, call it m. Report back with m and n, and we can design something...

 

[smash250]

Hi mike, thanks for replying mate. Problem is i do not have the old engine anymore and secondly its not off the flywheel its off the timing gear which i can not see. would it be possible to do a ratio off the RPM i posted? the 645rpm was the true value and the approx-380rpm was what was read on the dash board tacho. therefore 645/~380=1.69 if we round that to 1.6 could we not find/make some sort of pulse multiplier which takes the pulse signal and multiply it by 1.6?

cheers Ash

 

[Diver300]

Multiplying pulses isn't all that easy. You can use a Phase Locked Loop, but that isn't easy to get to work over a wide range of frequencies, and you would have to make sure that the oscillator would stop when the engine stops.

Is is possible to recalibrate the dashboard tacho? Some are set by a resistor.

 

[Mr RB]

I'm not sure if this device will drive the tacho properly but it does have a re-calibration range around 1.6 and should work with the inductive crank sensor;
Official home page of the Yellow Box Speedo Recalibrator

 

[ericgibbs]

Hi mike, thanks for replying mate. Problem is i do not have the old engine anymore and secondly its not off the flywheel its off the timing gear which i can not see. would it be possible to do a ratio off the RPM i posted? the 645rpm was the true value and the approx-380rpm was what was read on the dash board tacho. therefore 645/~380=1.69 if we round that to 1.6 could we not find/make some sort of pulse multiplier which takes the pulse signal and multiply it by 1.6?

cheers Ash

hi,
You could use two TC9400 back to back.

First TC9400 as a F2V and some resistive scaling then a TC9400 as V2F.