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Dyno Tuning to the Real Worldreal world dyno tuning

Speed's Secrets, November 2008

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A dyno tune-up can pay real dividends in terms of performance, but beware. Some dyno tuners throw big numbers at you, their idea being that more top-end horsepower and torque is always better, and they’re just the guys to give it to you so that you’ll be impressed by their work. Truth is, peak horsepower shouldn’t always be the goal of a dynamometer tune-up for your Harley.
The aim at Speed’s Performance Plus has never been to send a rider home with a dyno printout designed to impress his buddies. Instead, Speed’s goal is to make each motorcycle a better performing bike, one with crisp throttle response and a smooth, seamless powerband. The emphasis is to enhance power in the RPM ranges where the engine will be used the most. And for street riding that’s not necessarily top end, either, but instead from idle to about 5,500 or 6,000 RPM, with a real emphasis in the 2,000 to 4,000 RPM range. A savvy dyno tune like this will deliver crisp throttle response for kick-in-the-pants power delivery, improved fuel mileage, and a cooler running engine. And it could be the best couple hundred bucks you’ll ever put into your Harley.
On “mature” Harleys it’s a safe bet that some of the sensors regulating the EFI system have weakened, not to mention that many of the bike’s related mechanical components have gone a little soft as well. The piston rings probably aren’t sealing as they once did, the valve seal might not be as tight, the compression’s probably dropped a little. A good dyno tune will help readjust fuel delivery and timing to be more in sync with the bike’s current conditions, and the change can be dramatic. Rejuvenated performance will be felt immediately.
A dyno tune like that isn’t just for older bikes, though. Brand-new Harleys can reap the rewards, too. Factory-delivered, an OE Harley engine has its intake charge set on the lean side. It’s a fact of EPA life. But for maximum efficiency increased airflow with a corresponding increase in fuel is really needed. And if it’s an ‘07 or later Harley we’re talking about, Speed’s Wayne Hanson stresses the importance of sampling and adjusting the fuel mixture for both cylinders, front and rear. That’s especially true if you’re running True Dual exhausts.

Use of True Duals brings up another point: To achieve the most from a dyno tune-up, the air filter and exhaust should be enhanced with free-flowing replacements. “And ideally,” adds Jamie Hanson, “for a stock engine nothing smaller than a 2 3/4”-wide air filter should be fit. That’s the minimum it takes to move enough air.” Speed’s own high-flow Speedy Flow air filter kit addresses those factors, too. The Speedy Flow retains the OE cover, accepts most aftermarket covers, and uses Speed’s larger and deeper proprietary filter element that’s sized for 88”, 96” or 100”-plus engines.
A less restrictive exhaust system will help, too. Speed’s points to a 2-into-1 as the most efficient design, while equal length staggered duals can be effective, too, especially when they include a crossover pipe to balance the exhaust from cylinder-to-cylinder. And of course a Power Commander is mandatory for properly adjusting a fuel-injected engine; an adjustable ignition module goes on the carbureted models.
One more recommendation: with the bike in the hands of a trained person on the dyno, now’s the perfect time to make the switch to synthetic lubricants. Speeds discovered that running full-synthetic oil can drop engine operating temperature from 15 to 25 degrees. Couple that with the temperature drop achieved by a more efficiently running engine—and the synthetic’s increased lubrication properties—and it makes sense to make the swap.

Put all that together and you should see something in the range of a 13- to 15-percent increase in horsepower and torque. A significant gain, probably the best bang for the buck available in the street-performance world. More importantly, though, done correctly that increase will be right where you can easily access it and gladly use it.
A dyno tune-up isn’t just about big numbers. Instead, it’s a straightforward tuning combination that can make for a more efficient engine that offers the kind of grunt you’ll feel every time you crack the throttle. Check out Speed’s Performance for a dyno tune-up when they’re in your area. The net result could be more than satisfying.

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