There are dynos and there are other dynos.
Received today a Buell magazine called Battle 2 Win. (I also have a Buell),
which interviewed Gary Valine, who is runs Buell's special project dyno.
There is a comparatively recent dyno development to the the Dynojet dyno.
Dynojet dynos are relatively simple. Most of you know that the motorcycle
drives a drum and the dyno's computer calculates hosepower and torque as the
drum rotates.
The recent development to the Dynojet dynamometer is an "Eddy Current
Brake", which, according to Valine, is a Godsend in doing steady-state
developemnt work.
"The standard dyno is limited in that you can only do acceleration to full
throttle runs because once you reach a steady state , the power required to
keep the drum rolling is a fraction of that needed to accelerate it. And
this is fine if what you're looking for is a horsepower and torque curve.
However, if you'd like to tune and develop a motor at give rpm settings...
a standard dyno won't help you. That's where the eddy current brake comes
in.
Think of it as a very large disc brake attached to the dyno's drum. But
instead of being acted upon by friction pads, its rate of turn is controlled
by large adjacent electric magnets. As the dyno operator increases the
current flow to these magnets, the magnetic force - the eddy currents they
procuce are also increased, retarding the speed of the brake and,
consequently the drum.
Let's say you want to tune the motor at 3000 rpm. Without the eddy brake,
once you reach that figure, maintaining it would take only a fraction of a
horsepoower... virturally no load on the motor. However, with the eddy
brake, the operator can 'load' the motor to a point where it's tricked into
thinking it's acelerating, the same as if it were being ridden on the
street but, in our example, it is being held at 3000 rpm. Being able to do
this allows the dyno operator to determine optimal ignition and fuel
settings."
Another tip to assure that your dyno readings are accurate and repeatable is
to run your motor normally to operating temperature. Then, turn it off for
fifteen minutes before begining the dyno run. The waiting period allows
heat to permeate throughout the motor.
Rey Kirkman
VMOA #439
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