The horsepower and torque calculations are based upon the vehicle's weight
and acceleration.
Make sure that the active vehicle profile's weight setting is as accurate
as possible. The gross vehicle weight should be written near the latch of your
driver side door. The published GVW represents the weight of the vehicle plus
150 pounds for each passenger that the vehicle is regulated to carry. So
to determine what your vehicle weighs by itself, simply multiply 150 pounds by
the number of passengers your vehicle can legally carry and subtract this
number from the published GVW.
Acceleration is the most important factor in calculating horsepower and
torque. Therefore, you need to perform your dyno pulls on a straight road that
is as level as possible.
In order for ProScan to collect as many horsepower and torque data points
as possible for the specified RPM range, ProScan relies upon having an
accurate drive ratio for the gear in which the dyno pull is being made. The
drive ratio is used to determine vehicle speed in km/h from engine RPMs in a
specific gear. See Drive Ratio Calculator for
details.
You can attempt to improve the refresh rate by specifying a shorter
timeout value for the ELM microcontroller under ProScan Preferences.
A faster refresh rate will allow ProScan to collect more data points, thus
generating more accurate curves.
The vehicle must be kept in the same gear throughout the specified RPM
range. Vehicle's with manual transmissions should use 3rd gear. Automatics
should use 2nd. Be aware that performing a dyno pull may be troublesome in an
automatic vehicle. If you can't get a smooth RPM acceleration, you should use
the Track Performance tool for more
reliable results.
You should perform multiple dyno pulls on the same day, on the same
stretch of road, and in the same direction. After changes to your vehicle have
been made, go back to the same stretch of road and repeat the process. Compare
the before and after curves to determine how the changes have impacted your
vehicle's performance throughout the RPM band.
NOTE: The horsepower and torque curves will vary from those
obtained by a chassis dynamometer. No acceleration-based dyno tool can provide
accurate SAE measurements due to the many additional environmental variables.
However, if used properly, the ProScan dyno tool is an excellent means of
determining performance throughout the RPM band.
