On Monday, I dropped off my Vertex OAC magneto to Joe at Don Zig Magnetos for inspection and disassembly so that I could polish it. Labor charge for that is $125, including energizing the magnets and $150 to replace the coil. After running it on his test bench, the coil is indicating weakness when it warms up and I don’t want to take a chance with it. Vertex OAC magnetos have an internal coil, making them very simple, light, and compact. There is only one wire, a ground wire, needed. The ground wire on a magneto is to provide a path for the electricity to go to ground rather than to the plugs to shut off the engine. Magnetos such as the Vertex OXC and the Mallory magnetos have an external coil, just like any typical ignition. The advantage of an external coil on a magneto system is that the coil can run cooler and the mag can be made “hotter” (increased output) because it is not confined internally within the magneto housing restricted by size and heat limitations.
Magnetos such as the Vertex and the Mallory Super Mags have larger diameter magnets. Larger diameter magnets mean increased output at all RPM. The linear velocity of the larger diameter magnets throws a huge spark at low RPM. Every once in a while, I start buying into the propaganda of the magneto haters and start thinking that starting could be improved by changing the mag. To slap me back into reality, Joe at Don Zig’s placed a piece of all-thread against the housing of my OAC within about 5/8” from the exposed coil wire (cap removed) and rotated it by hand one click. The spark was every bit as intense as the MSD 7AL2 in one of my other vehicles. What I mean by “one click” is that magnetos are difficult to turn compared to a distributor. As the magnets align and misalign, you can feel the resistance from the magnetic attraction.
Magnetos are very reliable and will give you years of trouble free service. There are a few things that will kill the charge of the magnets in a mag: 1.) Welding on your chassis while the mag is installed. 2.) Polishing the mag housing. The static buildup of the buffing wheel will take charge out of the magnets, reducing output. If you want your mag polished, have it disassembled and polish just the case. 3.) Lastly, never connect battery voltage to a magneto; you will have a dead short.
A couple points on safety and prevention. 1.) You don’t want to turn a magneto without it being grounded. Even turning over the engine by hand produces and electric charge that needs to be discharged. If that charge doesn’t have a path to follow, it will make its own path, usually internally within the coil causing damage as the windings are shorted. 2.) Your mag should always be grounded while the engine is not running. Failure to ground the mag could result in any air/fuel mixture in a cylinder to fire just by rotating the engine by hand.
The only disadvantage of a magneto is that I see is, it is very difficult to integrate modern programmable timing controllers and rev limiters. There are rev limiters available for magnetos; one of my winter upgrades is a Dual Range rev limiter with RPM switch from ETC Inc.,
http://www.etcrevlimiters.net. I will write up my findings on this once I am able to get to the water to test it. With that being said, that is where the new MSD Programmable Digital-7 shines.
If you are seriously into drag racing, you will eventually end up with a programmable digital ignition. 1.) You can program in the RPM limit on the launch to control slippage or the “burn out”. RPM are ramped up to prevent over revving and blowing the pump dry on launch. 2.) You can program the advance/retard curve of each cylinder individually. 3.) There is an output that can be used for N2O that is triggered by timer or by RPM. To consistently run the number, a programmable digital ignition removes much of the driver error from the equation.
Something to keep in mind; when running a bad ass electronic ignition system, you need to have an equally bad ass charging system to keep up. Think of it like horsepower in an engine. You need enough fuel to feed the engine. “If you aint feed’n the horses, you aint got ‘em!” That Digital-7 uses 1.1 amps per 1,000 RPM. The greater the RPM, the greater the amperage draw. Then when you throw in bad ass fuel pump/s, N2O, and a kick ass stereo, you will need an equally bad ass charging system to keep up with demand. The 017 boat that I pit for at NJBA doesn’t have an alternator. At the end of the run, the Odyssey AGM is down to 60%. Even MSD has documented that as battery capacity diminishes, so does ignition output.
It all depends on what you like. If you are running a serious bracket boat, step up to the digital programmable. If you are running a river toy, any ignition system can be made to run well and reliable. As for me, I like and run mags in my boat and my street car with great reliability. In fact, I don’t even have an alternator in either.
Cheers,
Joe
