After installing a newer engine into an older european car (engine swap), I am trying to find a solution for driving the stock tachometer.
The old engine has a distributor/coil ignition where the tachometer is driven from the coil.
The new engine has the newer type ignition with no coil and a tach signal wire coming from the computer.
The signal from the engine computer will not drive this tach.
I do not have an oscilloscope but I may have enough information from simple DMM measurements. With the old coil ignition, the DMM set for AC Voltage shows around 28 volts and it wanders up and down a couple of volts. With the newer engine the meter shows about 18 volts on just the bare signal wire from the computer, and that wanders a bit as well.
With just those two measurements I am thinking the tachometer just needs a higher signal voltage to make it run. It's automotive so I have about 14.5 volts to play with from the alternator. I'm thinking maybe if I doubled the signal voltage supplied to the tach, that might make it go? I've been poking around for a while looking for solutions and I hit upon charge pump ICs that can take 15V and put out 30V using capacitors. Would that work, or does anybody have more insight on why the tach won't move?
The old engine has a distributor/coil ignition where the tachometer is driven from the coil.
The new engine has the newer type ignition with no coil and a tach signal wire coming from the computer.
The signal from the engine computer will not drive this tach.
I do not have an oscilloscope but I may have enough information from simple DMM measurements. With the old coil ignition, the DMM set for AC Voltage shows around 28 volts and it wanders up and down a couple of volts. With the newer engine the meter shows about 18 volts on just the bare signal wire from the computer, and that wanders a bit as well.
With just those two measurements I am thinking the tachometer just needs a higher signal voltage to make it run. It's automotive so I have about 14.5 volts to play with from the alternator. I'm thinking maybe if I doubled the signal voltage supplied to the tach, that might make it go? I've been poking around for a while looking for solutions and I hit upon charge pump ICs that can take 15V and put out 30V using capacitors. Would that work, or does anybody have more insight on why the tach won't move?