Speed’s Secrets October 2007

Performance Ignitions—Fire in The Hole!

Whether it’s a good old-fashioned carburetor or a set of injectors passing the fuel, neither will be much use if that fuel/air mixture isn’t lit with a big, fat spark at the right time. For real performance it’s crucial to match an optimized fuel mixture with an equally optimized ignition system (in terms of spark intensity and curve advance). That applies across the board, carburetors and EFI alike.

The benefits from a strong ignition are similar to what you’ll get with a properly tuned fuel system, and that’s crisp throttle response, and a smoother, more efficient and more powerful bike that’s just plain fun to ride. The guys at Speed’s Performance Plus routinely grab that brass ring, too. In fact, an ignition upgrade is always part of the plan when total performance is the goal. It’s a short and sweet shopping list; hot coils, a new and adjustable control module (either single- or dual-fire, and we’ll get to that in a minute), a pair of quality plug wires to deliver that hot spark, and, finally, the spark plugs themselves complete the list.

Begin with the adjustable control module. Modern Harleys use electronic ignition systems that are factory sealed and tamper-proof. That’s the first thing to change. Those factory modules rarely, if ever, deliver the spark a specific bike needs when it needs it. Throw in some common modifications like an air filter and exhaust swap, and it’s almost a guarantee that the OE advance curve won’t be anywhere close to where it should be for performance. Hence the adjustable ignition module, and there are plenty of good ones to choose from. Most plug in, replacing the factory part, and come with a selection of timing curves aimed at performance. And that’s just a starting point. These systems are ultra-adjustable, allowing for completely custom advance mapping and minute tweaking. Small timing changes can be made anywhere in the advance curve without having to throw out a complete ignition curve that performs well everywhere else. It’s all done with external control buttons and dials, and if you want to really get into it there are supplied software packages and laptop links. It’s easy work and it’s fun. Speed’s generally uses the Daytona Twin-Tec modules on carbureted bikes and the Dynojet Power Commander for fuel-injected models. They generally hold the ignition curves to a 6000-RPM redline, and the curve itself is always slightly different for individual bikes. Depending on the motorcycle, its modifications, the rider and the way the bike is used, the overall advance can end up anywhere from 30 degrees to 50 degrees total.

That covers adjustment. There’s also the choice of single-fire or dual-fire modules. Crane, Dyna, Accel, Daytona Twin-Tec and others offer the choice, and you should know that single-fire has definite benefits for the street. A stock Harley, of course, fires both its spark plugs simultaneously, and there are drawbacks to that. While one spark plug lights the charge in its cylinder, the other plug is sparking off in a cylinder that’s not on the ignition (or combustion) stroke of its cycle. The detriment here is that any residual fuel/air charge left in that cylinder will also be ignited and that can have the engine actually working against itself. Manufacturers of single-fire systems tout the power gains offered, but in actuality the guys at Speed’s have seen only moderate increases in horsepower and torque. What they have seen with a single-fire system, however, is a demonstrably smoother-running engine. Your choice.

High-output coils are also a must. Some deliver 45,000-plus volts, and while electrical engineers debate over the necessity of all that voltage and whether or not that juice actually makes it to the spark plug, what’s not debatable, according to Speed’s real-world experience, is the difference that high-output coils make. Here again the gain isn’t so much in dyno-sheet printout numbers as it is in seat-of-the-pants feel. Hot coils make for a smooth-running engine. Of course, those coils need to be matched with the best set of low-resistance wires you can find--Speed’s has their own--and two of the most reliable spark plugs you can screw in. Speed’s uses NGK.

All this is easy to do, and can be done right at home. To really dial-in that ignition, though, and perfectly match it to the bike, it’s money well spent to have a pro set things up. Speed’s Performance Plus does it all the time and their schedule takes them all over the country.

Article reprinted from Iron Works Magazine, Oct. 2007

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