Gas Engine Buzz Coil How-To

Learn how to make a simple, all-electronic buzz coil with David Cave as he walks through his process of building one.

| February/March 2020


A few years back, fellow engine enthusiast and friend Jim White threw me a challenge: Could I make a simple, all-electronic buzz coil? I had seen several schematics over the years, but all of them required two or three power transistors, some form of oscillator and an automotive ignition coil. The oscillators are usually the universal 555 timers, which require several resistors and capacitors around them, while the standard car coil is big and heavy. After giving the challenge some thought, it seemed there ought to be a much simpler way.

Looking for Solutions

The modern “single coil per cylinder” scheme used in newer cars uses, as the name implies, a separate coil for each cylinder that is activated by a small 5-volt logic signal from the engine computer. Starting with one of those coils would have several advantages: built in power transistor, built in trigger mechanism, and small size and light weight.

Using just three resistors, a General Motors LS2 engine coil and a capacitor, I created a pretty nasty buzz coil. By nasty I mean a much longer arc and a much faster spark rate than the old Model T-type buzz coil. After building one for Jim and another for myself, I put the project on the shelf. In fact, never expecting to return to it I threw the schematic away. Recently, however, the complex 555 timer system came up again on an engine website. That inspired me to find out how Jim’s was doing, and it turns out he has been using it for four years without a problem. Together with Evac 1 being so inexpensive and simple, I thought it was time to get it back off the shelf and try to remember the resistor and capacitor values. One key point is that it uses no pesky expensive semiconductors (transistors, integrated circuits, diodes, etc.) that can be put in backwards and blow up.

Make the Coil

(figure 1) A used General Motors LS2 automotive ignition coil, part no. H6T55171ZC.

Figure 1 shows one of the coils I picked up at a local junk yard. Four coils, with the wire harness, (one bank of a V8 engine) was very cheap, just $20 at the time. You can also find new coils on the internet for $20 or less. An advantage of the junk yard route, even if you only need one coil, is that getting the wire harness gives you the coil connector plugs (pigtail).


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