Turbo D

iTrader: (3)

Hey guys, have a odd question that I can't wrap my head around. On my turbo LQ4, I have the heat sink LS2 style coils running off my MSD 6010 box (preset dwell, not adjustable) at idle I have about 32-35 KV at all the wires read with my hand held kv meter. I switched to the newer LS3 type coils off my 09' Silverado and now at idle I have a around 15KV! So do these newer coils put out more amperage and less voltage? I just can't understand how the voltage can be half when it's jumping the same gap with the same cylinder pressure? What coil is better, the one that puts out 32kv at idle or the one that puts out 15kv? I was thinking with the LS3 coils I could run more plug gap since the voltage is lower? thanks in advance for your input.

smokeshow

iTrader: (17)

The coil output voltage is proportional to the turn ratio between the primary and secondary coils. It is important to remember that an inductor stores energy in the form of a magnetic field. The primary coil's field collapsing is what generates the potential energy to create a spark at your spark plug. But the field doesn't care how much current or voltage you need; it will collapse anyway. So the P=VI relationship I believe you are employing here does not hold for the coil pack. Negating losses, current induced in the secondary coil is proportional to the resistance of the coil/plug combination. The tighter the plug gap, the more current flows. For infinite resistance, no current would flow. Voltage would still be present as the field collapsed, but there would be no current.

That may be more confusing than necessary. If it was, I apologize To answer your question though, neither coil is actually better at idle. They both accomplish the same job. The 15Kv coil just does it with less voltage. Now the actual characteristics of the spark may change how quickly the mixture in the cylinder ignites, but that's another topic. Also, with lower voltage on the LS3 coils, you wouldn't run more plug gap; you would run less. Lower the voltage, lower the potential energy/ability to jump the gap. Higher cylinder pressures and big gaps need more voltage.

stevieturbo

How reliable is the meter ?

15kv sounds unbelievably low.

Circlotron

Actually the current flow does not change significantly with changes in plug gap, with an inductive discharge system at least. What does change is the duration of the arc. Smaller gap = longer arc time. Set up a scope on a test bench and see.

smokeshow

iTrader: (17)

How do you figure? Consider the extreme scenarios, infinite plug gap and zero plug gap. Infinite would flow no current and zero would flow maximum current. There is a function to define the in-between points and there logically must be significant changes to get from total current flow to none..

jimmyblue

iTrader: (11)

Your meter likely reads an averaged voltage and you
do not read the current simultaneously. A change
to the waveform that widens the pulse more than
2X could give you more energy in the gap. You can't
know.

Gap peak voltage is not the story, only the beginning
of it. Arcs have a negative resistance characteristic
and resistance drops once established, and more
current is more ionization is more current to some
extent.

A more inductive coil will push current longer and
have more stored energy to deliver into an equal
load. Coils deliver in constant current mode once
the (secondary voltage / load resistance) ceases
to be the limiting factor.

Now if you had a current waveform and a voltage
waveform you could readily compare delivered energy
and that would mean something.

Marketing on the other hand pushes whatever sounds
best, relevant or not, complete picture or not.