AEROMOTIVE Part 2
AEROMOTIVE Part 2 What is an aircraft engine? A child might answer, "an engine that's on an aeroplane." Foolish youth! If we skip the radials, rotarys, sleeve valvers, two strokes, diesels, turbines, jets, and rockets, we're left with . the four cycle, internal combustion, spark ignited, piston reciprocating, poppet valvers, in only; aircooled, liquid cooled, inline, opposed, vee, naturally aspirated, and supercharged gasoline consuming variations. These qualifications squeeze the answer into a set of characteristics that appears remarkably like an automotive engine to enthusiastic people. Back To The Basics: We can attempt to equate engine performance in a variety of ways. However, horsepower still seems to be the best method if it is qualified by an accompanying RPM (revolutions/minute). Power output in HP/CID (horsepower/cubic inch displacement) is a standard for most engine nerds but it doesn't reveal much about the drivability (torque) or personality (horsepower curve) of the engine. Torque and horsepower are intimately related even though they are often spoken of as if they were separate entities. I have taught a private engine design and building course for 21 years and it has always been a challenge to get my students to understand the relationship between torque and horsepower. This doesn't surprise me because these two parameters, ostensibly simple, are in fact tricky to relate. I am reluctant to rehash the whole horsepower/torque issue. But, based on conversations I have had with aircraft folks - and automotive folks, for that matter - I perceive the need to establish basic terms. We (“we” meaning us at Sunset Engine Development) are often asked, "what do I want, torque or horsepower?" Trying to explain such abstract concepts on the telephone cannot do the subject justice.
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