149 Copyright by Goodheart-Willcox Co., Inc. Chapter 7 Engine Size and Performance Ratings Technical Terms atmospheric pressure bore/stroke ratio brake horsepower (bhp) chassis dynamometer compression pressure compression ratio cylinder bore drive wheel horsepower engine displacement engine dynamometer (dyno) engine efficiency engine torque force frictional horsepower (fhp) gross horsepower (ghp) horsepower indicated horsepower (ihp) mechanical efficiency net horsepower oversquare engine piston displacement piston protrusion piston stroke power prony brake square engine taxable horsepower (thp) thermal efficiency undersquare engine vacuum volumetric efficiency work After studying this chapter, you will be able to: • Explain engine bore, stroke, and displacement measurements. • Calculate engine displacement. • Explain bore/stroke ratio. • Define oversquare engine and undersquare engine. • Describe piston protrusion. • Explain compression ratio. • Summarize rotational and angle measurement in degrees. • Explain how atmospheric pressure affects engine performance. • Describe engine horsepower and torque. • Explain various horsepower ratings. • Define volumetric, mechanical, and thermal efficiency.