Specific output
From Infogalactic: the planetary knowledge core
Specific output is a measure of engine performance. It describes the efficiency of an engine in terms of the brake horsepower it outputs relative to its displacement. The measure enables the comparison of differently sized engines and is usually expressed as kilowatts or horsepower per litre or per cubic inch.[1] Generally, forced induction engines out-perform naturally aspirated engines of the same size by this measure.[2]
