Tacho over reading
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Folks,
Have fired up the engine in my 1971 Sprint for the first time and the motor is running fine. As a precaution I fitted a new 23D type distributor and then put in a Lumenition Classic system. The tacho at idle appears to be reading twice the amount of revs, this was confirmed when we plugged in a rev /dwell angle reader, which showed 1000 rpm, when the tacho said 2000.
Has anyone had this occur before? I did a quick search, but seemed to find more about under reading than over reading.
Have fired up the engine in my 1971 Sprint for the first time and the motor is running fine. As a precaution I fitted a new 23D type distributor and then put in a Lumenition Classic system. The tacho at idle appears to be reading twice the amount of revs, this was confirmed when we plugged in a rev /dwell angle reader, which showed 1000 rpm, when the tacho said 2000.
Has anyone had this occur before? I did a quick search, but seemed to find more about under reading than over reading.
Cheers
Mike
Mike
- MikeB
- First Gear
- Posts: 41
- Joined: 30 May 2018
Mine also reads approx double with a Pertronix system, I?ve added a recommended interface box, but it?s still not right. Have abandoned it for a while due to fitting new kitchen for wife, but must get back on to it in the next week or so.
Change is inevitable, except from a vending machine!
- Bigbaldybloke
- Fourth Gear
- Posts: 894
- Joined: 16 May 2017
I assume the Positive to the coil feeds the signal to the tach, afterall if you are running points it?s the only wire connected to the loom ( the Neg only goes from the coil to the distributor).
So I suppose the question is how remote from the Coil positive does the Lumenition positive have to be, do you need to fit it via a relay with a permanent positive feed turned on by the ignition switch?
So I suppose the question is how remote from the Coil positive does the Lumenition positive have to be, do you need to fit it via a relay with a permanent positive feed turned on by the ignition switch?
Cheers
Mike
Mike
- MikeB
- First Gear
- Posts: 41
- Joined: 30 May 2018
Yes you need to take it from a supply turned on by the ignition switch that is separate from the positive that goes through the tach to the coil. The lumention generates a current pulse in its supply every time it triggers the ignition and this can be read by the tach and added to the pulse the coil generates
cheers
Rohan
cheers
Rohan
-
rgh0 - Coveted Fifth Gear
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