Perkins 4.108 Alternator PPR Calculations

[BigAl.NZ]

Hello,

I am adding a actisense to my 4.108 engine to get digital engine data.

The manul says I need to work out the PPR (Pulses Per Revolution).

My alternator has 12 poles (6 each side).
Crank Pulley has dia 130mm
Alternator Pulley has dia 65mm

I then got (12/2) * (130/65=2) = 6*2 = 12PPR

That should about correct?

Another issue I am having with the install is that the old analog RPM gauge doesnt go but the flast digital one doesn (although it bounces which was what the old was doing right before it stopped.

How can one go and on not - they are on teh same endine sender and siring loom?

Cheers

Al