Speed’s Secrets April 2008
The Dyno Tune
With the riding season on tap, you’ve no doubt completed your pre-season maintenance. You’ve installed new spark plugs, changed the oil, checked the various fluids, adjusted the drive belt and aired up the tires. But you’re not done, especially if that Harley has a couple years and some miles on it. And especially if it’s a fuel-injected bike. A professional dyno tune is in order about now, and if done right you’re going to love the result.
Truth is, over the years and the miles it’s a safe bet that some of the sensors regulating your bike’s EFI performance have weakened. The bike might seem to run fine, but you’ve just gotten used to its diminished performance because the deterioration is gradual. A sensor—and there are many of them on an EFI Harley—that’s operating at the bottom of its voltage range will call for a fuel/air mixture considerably different than when at its peak. This doesn’t mean the sensor is bad. It just means that the motorcycle needs readjusting and that’s where a pro dyno tune comes in. Along with sensor wear, chances are that everything mechanical has gone a little south, too. The piston rings aren’t sealing as they once did, the valve seal isn’t as tight, and cylinder compression has dropped just a little. The net result is less intake draw. But this doesn’t mean the engine needs rebuilding, it just means the fuel/air mixture needs recalibrating. And with everything readjusted to this new—let’s call it mature—status, your engine will feel crisper, the throttle will be more responsive and the bike’s ride will be smoother overall. You might even notice a bump in fuel mileage. A good dyno tune by a savvy pro can deliver all that and more. But how do you know you’re getting a good job?
“Well, a couple things come to mind,” says Wayne Hanson of Speed’s Performance Plus. First is operator experience. Wayne warns that it’s imperative that the tuner is knowledgeable, and he knows whereof he speaks. Wayne and his sons Jamie and Jason have tuned tens of thousands of motorcycles over the years. They’ve seen it all and fixed most of it.
Next, Wayne says if it’s a fuel-injected bike you’re dealing with, be sure the dyno operator has the knowledge, equipment and ability to check the voltage levels of all the bike’s sensors. The crank sensor, the throttle-position switch, the temperature switches and the positioning of the IAC motor and its controls play critically important roles in the timing and performance of the engine. If there are weaknesses here, any further tuning is largely a waste of time and your money. And of course the tuner should be inspecting everything in the fuel delivery and ignition systems, too. At Speed’s Performance, an EFI tune includes a careful check of the fuel pressure. Wayne and his team check for air leaks, they’ll verify the health of the spark, they’ll make sure the air filter is clean and they’ll inspect all the fluids. In short, a critical eye is cast over the entire motorcycle before it goes on the dyno. At Speed’s Performance they’ll often do a full-service on the bike first, changing the oil to the Lucas synthetic they so strongly recommend, and they’ll install a fresh K&N Performance Oil filter. After, and only after, that, the dyno tuning can begin with adjustments to the air/fuel ratio, rate of fuel delivery and the ignition timing.
One more thing: If it’s a 2007 or later Harley we’re talking about, Wayne stresses the importance of sampling the fuel mixture for both cylinders, especially if you’re running True Dual exhausts. If the dyno operator can’t individually map the fuel curve for both cylinders you’re not going to get a good job. It’s simple as that.
What will this cost? At Speed’s a complete dyno tune on a carbureted bike—which will probably include new spark plugs, wires and maybe some other parts like filters and breathers—generally runs between $150 and $250. On a fuel-injected bike that’s loaded with sensors and pumps and switches that need checking and possible replacement, the bill can be anywhere from $300 to $450, and that’s assuming you already have a Power Commander installed. Either way it’s money well spent. Well spent, that is, if you’ve first done your homework and brought your bike to the right dyno. Speed’s Performance, of course, brings that dyno—and all their experience—to you all season long at events across the country. Check the SPP website for their schedule.
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