SuperFlow AutoDyn, Руководство оператора

Страница: 199 / 208

Supplemental Information
Appendix A - Page 204
AppA General Testing Information.fm
A more important determinate of power is the engine stroke. The speed at which an engine
develops its engine power is usually determined by the stroke. Typically, maximum power is
developed when the average piston speed is between 4,000 and 4,500 ft/minute, (20 to 23 meters/
second.)
Because power is equal to torque multiplied by speed divided by a constant (HP = torque x speed
/ 5,252.113), and because the maximum torque for a given displacement is constant, the power
per cubic inch is directly proportional to engine speed. Since engine maximum speed is inversely
proportional to engine stroke, the shorter the stroke, the more power per cubic inch the engine can
develop.
For example, an engine with a 3-inch stroke will develop maximum power at approximately 8,000
rpm, while an average engine with a 1.5-inch stroke will develop maximum power at approximately
16,000 rpm. While the maximum torque per cubic inch will be exactly the same for both engines,
the maximum power per cubic inch will be twice as great for the shorter stroke engine.
A.7 Fuel Injection Return flow
Many new injected engines bypass part of the fuel and return it to the fuel tank. This introduces a
problem in measuring total fuel flow. While the SF-902 dynamometer can be configured to subtract
the fuel flow in one channel from the fuel flow in the other, this frequently produces errors due to
temperature difference, aeration, and pulsation problems.
Figure A-1 Fuel Canister Schematic