Anatomy of a Vintage Smoke Dyna-S ignition!

 I'm not sure about your info H2 tuner.  @ 2.3 bar I have run .038 gap with Bosch iridium plugs in motors turning under 6500rpm, and .036 in motors turning 6800rpm and up.
 The MDS  6AL, is 45,000 volts continuous with NO drop in voltage unless input voltage drops below 12.7  As stated by Yote, the purpose of a larger spark plug gap is performance driven, creating a larger kernel effectively burns the fuel charge more complete. Cleaner emissions is just a byproduct of that burning.  There is no way to create a large enough "kernel" to burn all the fuel going into a cylinder on a high performance engine.  Forced induction, and long duration,  high lift cam shafts mandate a MSD type system to burn all that fuel. With a spark time of  20degrees crank rotation from an MSD is the most effective way to create a larger "kernel"
A  T/F car, runs twin Rare Earth MSD mags. 2 plugs per cyl. They use a 3/4 in. reach plug gaped at .070 If they take too much advance out, they drop cyls. Not because of the compression ratio, but because of how much fuel is pumped in under pressure

Originally posted by Vintage Smoke h2tuner, Lots of great info on the HEI!!!   I am sure everyone here would love to hear more about it when you actually devolop a kit for the RD's.   Especially if it offers an improvemnet in performance, features, and price point of systems already available such as my Dyna kit or the MZB available from John at Economy Cycle.   Please start your own thread and tell us all about it when you do!! I'll be looking forward to it.

A key advantage of the MZB is its stator/generator with 125W ouput and coil voltage is >35K. Although Borut @ Zeeltronic is testing stator/generators for production now. And of course with the Zeeltronic the MZB has a fully programmable curve and 3 stage rev limiter, dig tach output, etc. Its pricey, but its the schiznit. The ignitech system is similar but I have no experience with it.

Just to make sure we have our nomenclature correct.
Kernel refers to the first small turbulent eddy that ignites.
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To Quote Wiki "The spark across the spark plug's electrodes forms a small kernel of flame approximately the size of the spark plug gap."
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Once a flame Kernel is initiated, it is up to the turbulence(rotational rate) of the small scale eddies that are around 1 mm in diameter to spread the combustion to neighboring eddies.
These small spinning eddies are ignited on the surface by coming into contact with already burning spinning eddies.
The eddy itself burns inwards at only the laminar burning rate which I believe is about 20 meters per second.
The speed of the combustion process relies on the rotational speed of the eddies to allow them to ignite larger numbers of neighboring eddies, and increasing the spin rate of the eddies is caused by increasing the level of turbulent intensity.
The turbulent intensity is created from the kinetic energy of the bulk flow, which is the result of transfer port aiming and piston motion but mostly from squish action.
This is why the squish band is so important in a 2 stroke engine that unlike a 4 stroke does not depend on tumble and swirl to create turbulent intensity.
Without turbulent intensity and spinning eddies, the laminar burn rate would only allow engines to operate at between 1,000 and 1,500 RPM.


Hope this helps,
Dave

Wow, LOTS of ignition system info for all to digest, most of it somewhat incorrect.

And, yes, I am aware of the Top Fuel/Funny Car/Alcohol mags, having been doing ones for 5 teams for over 12 years. And, those mags ARE stable with increased gaps. However, it ISN'T the fuel load that makes lighting off the fuel hard, it is the added compression, up to 5 positive atmospheres, that cause problems. Since fuel isn't compressible, the sheer volume of it injected into a load engine causes comp ratios to go right to the moon. This IS one of the two reasons that those engines need two spark plugs. The other reason is, load (nitro) burns somewhat slowly in comparison to alcohol and gasoline.

All the teams I am aware of, don't run .070 plug gaps, they are back down to .050. since sanctioning bodies lowered the percentages of nitro that can be used, the blower drive ratios have been 'readjusted", and, more pressure is being used in the engines.

Those magnetos are so far advanced over the ignition systems we are speaking of here, they have absolutely no comparison between them. 

Also, in a two stroke engine, it isn't turbulence in the inlet, nor transfers that as essential to getting the compustion chamber filled correctly, it is the angles of the ports that enhance the loop scvenging of the fill. Putting the mixture in the right place is essential to getting the right fill and burn. If the ports don't fill the chamber correctly, and fully, we get lean spots, loss of power, increase of heat, lots of other problems. The port angles also rely on correct squish/quench distances also, but that is for a different discussion on engines.

In the early 1970's, we tried a special set of heads on an H1R 500 triple Kawasaki road racer. Two plug holes in the heads, at 45 degree from center angles, front to rear. We only used ONE plug per cylinder. What we found was that with the plug in either hole, the engine ran virtually the same, buit, was extremely hard to start with the plug in the front hole, lit off easily in the rear hole. When we angled the transfers, we got homogenous performance, easy starting no matter the end we put the plug in.