Why dont you measure engine output in terms of horsepower?
Simply, our method of reading pressure is much less expensive. A pressure reading serves as a reference point, as does a horsepower reading. Our method of measurement makes the Dynamometer affordable to every dealer. It is important to realize that when the manufacturers assign a horsepower rating to an engine, it is done under optimal conditions (i.e., a specific altitude, temperature, barometric pressure and humidity levels). This, coupled with the fact that they are allowed a +/- 10% margin of error in production, means that you would rarely see an engine producing the exact horsepower for which is was rated.
