Hi all.

I have recently bought a Ignition Spark Analyzer unit. It has an inductive clamp that goes on each spark plug lead and the unit then shows the Peak KV and the Burn KV.

What I'm wondering is what would be the normal KV reading on each lead. I have tested all mine and they range from about 7 to 9 KV. (305 TPI HEI remote coil)

The book that came with the unit in all its' examples shows reading around the 22kv. So I'm a bit worried that either I'm low on KV or the unit I have is not reading it right.

Any ideas?

 

I would say 35,000v to 50,000v is pretty normal.

 

I think that they are supposed to generate 35 to 40 kv at the coil.But by the time you start throwing losses in from the coil to the rotor and then across the rotor gap and thru the wires that number is going to get whittled down fast.Double check it against other cars to get a real world idea of what numbers you are going to see.

 

10 KV would be about right for arc-over on a normal engine. See the reference here:
Spark Plug Wire Test

 

Yeah well I have tested it on about 3 other cars and they all seem to be around 10 - 15 KV, so I guess thats about right then. Where does the 50,000 Volt writen on the side of these coils come in to it!

 

Advertising blather would be a charitable description.


The figure of importance for a spark is its contained energy (joules), not volts. And coils have very little to do with the energy in the spark.

It's difficult to print all that on the side of the coil.


FYI-

Coil energy is defined by:

Energy = [ 1/2 L * I * I ]

where L = coil inductance {Henries) , I = coil current (Amps)

The current comes from the ignition module. GM 7- or 8-pin modules make 6 to 7 amps; GM HEI coils are around 8 mH inductance.

Try finding those specs in the next 'High Energy Ignition!' advertisement you read.

An excellent coil simulator is here, if you wish to do a more detailed evaluation:
Ignition Coil Simulation

 

-5-15Kv is normal
-no more than 3Kv difference between each cylinder
-if you have low Kv (ex. 3Kv) then that means low resistance on secondary side
-if you have high Kv (ex. 28Kv) then that means high resistance on secondary side

 

Thanks so much for the info. You seem to really know your stuff.

I was wondering lets say if you were changing spark plugs, and put a new set of brand A in then took readings, then put a new set of brand B in. If the KV was over all higher or lower what would be better?

Also, what I noticed is that when I replaced all my 8mm leads with 9mm ones the analyzer could not get a reading off the leads. Is that normal? I was thinking the new 9mm leads must have really good suppression. When it did seem to get a reading it would just re-set and go back to the start up menu.

Thanks so much again.
Francis.

 

i would just use oem plugs.

there is more insulation on the 9mm wires so you will get a little weaker signal on you scope

 

Thanks mate. Yeah I was just curious as to what would be the think to say one is better than the other. Like is a lower voltage going to mean it's working better? BUt yeah I do always try to use the factory parts.

Hey out of interest, what are your thoughts on Coils. Lets just Say "a stock replacement universal oil filled Electronic Ignition coil compared to a MSD Blaster oil filled Electronic Ignition coil. IN the real world would there be much difference to be gained by the 3 times more expensive MSD?

 

to be honest i dont know if you would gain or not??