is the ability to overcome rotational resistance. High
compression, large displacements, tight rings, blowers,
and other factors all offer rotational resistance -
and it takes torque to overcome this. Unfortunately,
starters are rated in kilowatts. This is a measure of
its torque and speed combined. The torque output is
like engines, have different powerbands. Some have a
maximum power point at a relatively high RPM with little
torque. Whereas others produce more torque and yet lower
RPM. In the performance environment, torque is the most
important consideration, generally because a performance
engine offers more rotational resistance than stock.
As a result, kilowatt ratings can be confusing because
two starters with the same kilowatt rating can have
very different torque characteristics.
engine will demand a certain amount of torque for cranking.
When the torque demands cause a starter to exceed its
maximum power point, the extra input energy is wasted
as internal heat. Asking a starter to produce more torque
than it is comfortable with results in low electrical
to mechanical efficiency and drastically increased internal
heat. This is what causes premature starter failure.
The key is to use a starter that has a power peak at
a high torque point. Then, in the event that the cranking
conditions offers high resistance, the starter will
have the torque characteristics to handle it without
other factors effect starter performance dramatically.
Voltage is very important. Cabling and quality disconnect
switches are important because under heavy load, voltage
will be lost or "dropped" in undersized or
hot cables, or hot switches. The internal resistance
of the battery itself results in decreased voltage to
the starter. Therefore, low internal resistance batteries
like typical 1000CCA - or better yet - spiral cell AGM
batteries such as Optima and others should be used.
High voltage batteries like the new 16 Volt Powermaster
battery is a perfect choice for any racing application.
you purchase a Powermaster starter you will get a dyno
sheet that shows you the exact performance of your starter.
The sheet itself will explain how to interpret the data,
but you can be assured that Powermaster starters are
built to a consistent, statistically controlled standards,
and that they are dynamically tested throughout their
entire power range.