FAQ'sFrequently Asked Questions
What is a dynamometer?
A dynamometer, or dyno as it's normally called, is a machine used for testing of vehicles in exacting and repeatable conditions. With a dyno you can run a motorcycle at nearly any speed and measure the computed horsepower by how hard or fast it spins the drum inside the dyno.
What is tuning?
An engine runs best with a correct ratio of air to fuel called stoichmiometric mixture. That mixture is generally between 13.2 through 14.7 parts air to 1 part fuel. When the motorcycle is running on the dyno the exhaust gas is analyzed to determine if the mixture is correct. Too much fuel and the mixture is "rich" and too much air and the mixture is "lean". A motorcycle can be lean at some RPMs and /or throttle positions and too rich in others. Changes are then made to the motorcycle's fuel injection or carburetors to correct the fuel ratio and thus obtain the most potential from the engine.
How is the motorcycle tuned?
On a carburetor, changes are made by replacing or adjusting parts of the carb. Parts like jets and needles that control the flow of fuel can be replaced or modified with a "jet kit". Fuel injected bikes can be modified with a Power Commander or by reprogramming or replacing the stock computer.
How does a Power Commander or a Bazzaz work?
Inside the computer of fuel injected motorcycles is a "fuel map". At given throttle positions, RPMs and other factors like air density and temperature the computer uses the fuel map to tell the fuel injectors how much fuel to spray into the engine. When changes are made to the motorcycle that effect the amount of air the engine uses (like an aftermarket exhaust or air filter) then changes to the fuel map need to also be made. A Power Commander intercepts the signal going from the computer to the injector and modifies it to add or subtract the right amount of fuel to make the appropriate air / fuel ratio.
What is Tuning Link and how does it work?
Tuning Link is a software program developed by Dynojet for use with their dynos to tune their Power Commanders. While the bike is being run on the dyno at different RPMs and throttle positions the air / fuel ratio is constantly being computed. Changes to the Power Commander are made automatically by the Tuning Link software while the bike is running! Before Tuning Link the motorcycle would be run through the RPM range on the dyno at a given throttle position. Then the air / fuel ratio is calculated by the dyno operator at different RPMs of the run. Those calculations are then entered by hand into the Power Commander. Another run is then done at the same throttle position and differences noted. That cycle continues until the dyno operator is satisfied with the "tune". Then Mike (Our Ceritified Research Expert) puts his knowledge of tuning to work to give you and equal balance of gas mileage and performance where the bike likes it.
Do I need a custom map?
There are a lot of downloadable Power Commander and Bazzaz maps. Just as off-the-rack clothing of the same size may not fit just right, custom tailored clothing is made exactly to your size. Every bike is a bit different so not every map fits every bike. Even with a map that was made on the same bike with the same equipment there is always room for improvement.
Does dynoing hurt the motorcycle?
No more than riding it on the road does.
Why are dyno readings between dynos different?
Horsepower is a computed figure based upon how much torque an engine produces. The torque of the motor is measured on a dyno by how quickly it can rotate a drum of a given weight. Several variables like bearing wear, lubrication, temperature, etc can effect how easily or hard the drum can be rotated thus skewing the torque reading of different dynos or even the same dyno on different days. An eddy current dyno produces more repeatable and consistent results by controlling the speed of the drum that the motorcycle is turning. The DynoJet 250i also samples air pressure, temerature and humidity within the room. It uses this data to apply a "correction factor" to the computed data. Since engines generally run better in cooler air with less humidity the motorcycle run at different times could show different output readings. The correction factor ensure that the operator is comparing "apples to apples" when looking at runs from different times.
How do you read a dyno sheet?
We normally have 3 lines on our dyno sheet: horsepower, torque and air/fuel ratio.
This sheet shows three dyno runs from the same motorcycle. The motorcycle was run in 4th gear at 100% throttle position.