Lot's of good questions, skip if not interested!
chacaocop1 wrote: I was not aware of the 3 ohm "rule" that makes the voltage drop (basic Ohm law) in order to have the right spark for the truck.
Yep, that's it. 12-14v in a 3 ohm coil primary is 4-5 Amps. whether fed with 24v and a dropping resistor or 12v without, it's still the same coil current in the inductor, which will yield the same magnetic field to the transformer. And thus spark.
Correct me if I am wrong, but according to my limited knowledge, the hotter spark means that the "arch" generated will be more powerful creating a bigger electrical discharge and as a consequence burning more gasoline in a shorter time giving more power to the engine. Even the EPA does not mind bigger coils since the gasoline will burn better.
Like most things in automotive performance, this is true only to the extent that you are removing a constraint.
Otherwise we'd all have giant coils on our cars.
Clearly a weak spark results in incomplete combustion, or no combustion at all. So hotter spark rarely hurts unless you carry it too far.
But you reach a point when diminishing returns kicks in. Hotter spark does not return improved results to justify the expense.
If it did, we'd all run super hot coils by default. Mfg's clearly know how to do it, and in fact usually temporarily make the spark hotter for cranking by bypassing the ballast.
But now I have a question for you. I have read many ads for VW hotter spark coils, etc and has always been interested in applying it to my pinz.
Have you ever tried installing a pertronix HV coil in a Pinz? Can I assume that my assumption is correct and my Pinz will run better with it?
This was a really big deal in 6v vehicle days. In 12v later days the bosch blue was the "hot" upgrade, and the pinz effectively has that stock.
Some of this is system voltage related in the sense that coil primary voltage could sag a bit with small alternators & heavy electrical loads. Or at low RPM. My pinz coil problem way back was at idle, ran fine at speed. But the spark was blowing out at idle due to lower primary voltage.
The flamethrower concept is similar to the bosch blue, and they have models that carry it further.
There are two ways to get hotter spark on kettering point systems:
- More efficient coil: Same resistance (and thus same current), but with larger wire (lower resistance). Which allows more windings, more magnetic flux transfers across the transformer, and you get hotter spark. Sometimes they increase the turns ratio in the transformer, creating more voltage since they have more current.
Decrease coil resistance: the poor man's approach is to lower the coil resistance, allowing more current. But putting more stress on the ballast resistor (heat) and switch/relays. Some systems can handle it, others are more borderline. Or you can just not use a ballast resistor. You'll see some coil heating due to the prolonged current. But works OK for a short race.
In points days the coil current directly impacted points life. With devices like the pertronix or other electronic points replacements, this is less of an issue.
Coil heating comes from the internal resistance. Bigger wires == lower resistance == more current without heating == hotter spark
So the $60-70 Pertronix coil is the extreme upper end of the coil. Big wires, more efficient, etc. Available in standard coil resistances, which is good.
The cheaper flamethrowers are more like the bosch blue. Better than a plain stock coil. Some folks put the lower resistance ones on, which is a typical race thing, but system life will suffer.
Myself, I found the bosch blue true 3 ohm coil to make a bright blue, fat spark. Noticably better. And cost me every bit of $24 at my local VW specialist.
Caveat:
1) All of the above changes a bit with resistor plugs, and or resistor wires. The normal bosch ignition can handle one or the other, but not both. Bosch platinums pretty much come only in resistor form, and there are zillions of posting of folks who badmouth bosch platinums. What it really is that they are using resistor plugs with resistor wires, and the normal coil just is not hot enough. Use one or the other! Modern cars go super high voltage to allow both resistor plugs & wires for interference reasons. Also idle emissions, etc.
2) Plug heat range has an effect. Jake & others know far more about this then I ever will, but you can get too much spark/heat and run into problems. Hard to do with points systems, but it can happen.
Net-net: a $25-35 bosch blue or normal flamethrower combined with civy dist/wire conversion is a big win on pinz's. I'm not sure I'd spend $70 on the super flamethrower until I did that and found it wanting.
And of course, distributorless is the biggest win!
Have fun,
Alan