More on dynamometers: Horsepower vs. torque

Publish Date: 
Jul 17, 2014
By Tracy Martin

So how can any horsepower and torque numbers be useful? Remember that a motorcycle manufacturer uses horsepower and torque numbers to sell motorcycles. It tests its engines under ideal conditions, measures power at the crankshaft and does not account for power loss due to the rear tire, shaft, belt or chain drives.

Manufacturers can’t “adjust” numbers too drastically due to legal issues with advertising claims, and most use SAE correction factors to level the playing field.

Magazines are a mixed bag regarding how they get their performance numbers. The better magazines will use the same dyno and operator to get all the hp numbers for the bikes they test and with correction factors (air temperature, barometric pressure, humidity) applied.

Comparing one magazine’s numbers to another is pointless because of the variables in just about everything related to testing. The only time horsepower and torque numbers become serious is when a rider is going to spend money. If an aftermarket exhaust system and other performance parts are going to be installed, and the desired outcome is a different exhaust note and some bragging rights, then horsepower numbers are immaterial. If the gain, or loss, in power is important, then measuring power output needs to be approached with some common sense.

Even if your dealership doesn’t have a dyno, you can still have your customer’s motorcycles tested by contracting with a portable dyno services. When choosing a service, interview the operator before sending your customers over. The hp and torque numbers you get are only as good as the operator.

Ask how long he/she has operated a dyno, what types of bikes they have experience testing, what correction factors are used, what brand of dyno they have, how they maintain it, and what charts and graphs will they provide to your customers. Most importantly, will they take time to explain what the numbers mean, so your customers will understand?

Whether you have a dyno or not, you need to provide basic education to your customers about what they can expect from having their bike dyno-tested. Are they looking for all-out performance, better street-riding performance or fuel mileage? If customers don’t know why they want their motorcycle tested, and what they hope to discover from the hp and torque numbers, the dyno operator won’t either.

The only numbers that really matter are the ones that are consistent and trustworthy. Dyno runs can be used to see if a new exhaust system, or other component, helped or hurt an engine’s power output. Tell customers that comparing horsepower and torque numbers with riding buddies or magazine test results is a zero-sum game and can lead to “horsepower unhappiness.”

Instead, dyno testing should be used to educate your customers about their performance goals and to keep your dealership informed and up to date about the parts and services it provides.