Peak horsepower numbers are impressive for "bench racing", but the area under the horsepower curve over the usable rpm range at real world temperatures actually wins races.

Engine power is highly dependent on atmospheric conditions especially temperature. SRS engine packages are tuned to give their best performance at the temperatures and track conditions they will actually encounter. An engine can be tuned to make an impressive dyno “trophy pull” for bragging rights by running the engine at less than operating temperature on a cool dry day. That same engine may not perform well or will be unreliable on the track.

SRS does dyno development under conditions as close as possible to those encountered on the track and then the results are verified on the track. SRS uses a Davenport Engine Dynamometer to record engine performance under controlled conditions. The horsepower is recorded every 100 or 200 rpm in the rev range of interest. The horsepower data recorded are plotted on a graph with horsepower on the vertical axis and rpm on the horizontal axis. This plot is the horsepower curve. The “area under the horsepower curve” referred to above is, in simple terms, the average horsepower over the rev range that the engine uses.

Engine horsepower is a function of torque and rpm and the dyno’s job is to record this data accurately and repeatably. The Davenport dyno’s computer samples torque and rpm up to several thousand times per second and has demonstrated repeatability in the range of 0.5%. That means a power curve on a 20 hp engine can vary as much as 0.1 hp due to the “randomness” of the dyno. You can see that if you are searching for tiny bits of power from engine tuning tweaks, the dyno must have very little “randomness” so those small power changes are not masked. The idea in most dyno tuning sessions is “Crumbs make a cake.” That is why dyno tuning is so important today. An accurate dyno can detect small power gains that would be almost impossible for a driver to detect during track testing.

For more detailed information about how SRS conducts kart race engine dyno testing, go to www.srsengines.com or call us at 903-769-4140.