timing light rpm reading double, affect timing?

[drewbuddy]

i have a digital innova timing light with a tach on it and when i hooked it up to time it was reading 1500- 1600 rpm and my tach (in car) was reading bout 750 800rpm. Hooked it up to buddies van and was reading correct. Not sure why it's doing this, will it affect when I timed it? Or do I have another issue i am over looking, cause it definitely wasn't revving that high. Not really sure what to think. thanks for any help on this

 

[pauleyman]

Our cars use a waste spark ignition. You notice that the coils are in pairs and not four individual. So when a pair fires it fires on the power stroke of one cylinder and the exhaust of another. That also means each cylinder receive two sparks for every power revolution or once per actual revolution. Timing lights assume the once per power so RPMs read double on this type of ignition. There may even be a setting to allow for that.

 

[drewbuddy]

ok thats what a buddy sugested, no setting for this crappy tire gun. Thanks for the reply