Air Cooled Engine Technology. Roth 9 th Ch 6 Engine Performance Pages

Transcription

1 Roth 9 th Ch 6 Engine Performance Pages

2 1. Internal combustion engines belong to the engine category. Gasoline Diesel Heat

3 2. The heavy flywheel provides the necessary to keep the crankshaft spinning during the non power strokes. Inertia Momentum Reaction

4 3. Engine performance is defined as the that engines do & how well they do it. Force Torque Work

5 4. Engine is the diameter of the cylinder. Bore Stroke Displacement

6 5. Engine is the length of piston travel. Bore Stroke Displacement

7 Square Engine: Bore = Stroke Over Square Engine: Bore Greater Than Stroke Under Square Engine: Bore Less Than Stroke stroke engines/

8 Square Engine: Air Cooled Engine Technology As a square has both the sides equal, here also the Bore and Stroke are of almost same size. The engine tries to strike a balance between torque and top speed.

9 Long Stroke/ Under Square Engine: As the name suggests the Stroke is longer than the Bore. Due to the longer stroke, the engine makes good torque at relatively low rpms. It is important where the bikes pulling more (torque) at relatively low rpms is more important than the top speed.

10 Short Stroke/Over Square Engine: As the name signifies the Stroke is shorter than the Bore. Due to the relatively shorter stroke, the engine revs fast and is more suitable where a quick build of power is important, more importantly where the bikes make power at higher rpms.

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12 6. A crankshaft with a has a stroke offset would yield a stroke x 2 = Throw Journal Diameter

13 7. Cylinder is defined as total cylinder volume with the piston at BDC of travel. Bore x Bore x Stroke x =.785 Bore Stroke Displacement

14 8. Engine displacement is the volume of 1 cylinder at BDC multiplied times the number of. Valves Cylinders Camshafts

15 9. The formula for engine displacement is: Bore x Bore x Stroke x.785 x # of cylinders If: Bore = Stroke = Displacement = [ ] cubic inches [ ] cubic centimeters x x x.785 = 9.0 Cu. In. If: Bore = Stroke = Displacement = [ ] cubic inches [ ] cubic centimeters x x x.785 = 19.4 Cu. In. If: Bore = 6.5 mm Stroke = 4.5 mm Displacement = [ ] cubic inches [ ] cubic centimeters 6.5 x 6.5 x 4.5 x.785 = 149 Cu. Cm.

16 10. ratio is the BDC cylinder volume compared to cylinder volume with piston at TDC. (Here s why compression ratio is so important!)

17 11. If Displacement = 250 cc s Combustion Chamber Volume is 10 cc s Compression Ratio = = 25:1 Compression Ratio (diesel) = 10:1 Compression Ratio (gasoline)

18 12. is any push or pull on an object. force acts in a circular or curved path. Force, Momentum Force, Centrifugal Force, Torque

19 13. is a force per given unit of area like pounds per square inch Force Pressure Area

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21 14. If 200 pounds of force are acting on 2 square inches of area, the pressure would be: psi The guy weighs 200# & the car weighs 2000# If the piston he s standing on has an area of 100 in 2 What area does the output piston have to be to lift the car? = 100 psi

22 15. is accomplished only when a force is applied through some distance. Work is measured in units of foot pounds. One foot pound of work is equivalent to lifting a l pound weight a distance of 1 foot. Work is always the force exerted over a distance. When there is no movement of an object, there is no work, regardless of how much force is exerted Force Torque Work

23 16. is the rate at which work is done. POWER is the rate at which work is done. It takes more power to work rapidly than to work slowly. Engines are rated by the amount of work they can do per minute. An engine that does more work per minute than another is more powerful. Power Torque Work

24 17. 1 horsepower is ft lb of work in 1 minute or ft lb of work in 1 second. 33, = 550

25 18. 1 horsepower = 746 watts. A 10 horsepower engine would be called a watt or kw engine. 10 x 746 = = 7.46

26 19. horsepower (BHP) is the actual usable horsepower delivered at the engine crankshaft. Brake Indicated Frictional

27 20. A loads the engine & transfers the load to a measuring device to determine HP. Tachometer Dynamometer Thermometer

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32 21. horsepower (IHP) is the power developed by the burning fuel mixture in the engine. Brake Indicated Frictional

33 22. horsepower (FHP) is the horsepower lost due to friction in the engine. Brake Indicated Frictional

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36 23. IHP FHP = BHP If an engine should have 12 HP but it maxes out at HP, what is the FHP? =.75 FHP

37 24. An engine s horsepower (RHP) is generally 80% of its maximum brake horsepower. Rated Indicated Frictional

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39 25. is a twisting or turning force. Horsepower Torque Speed

40 26. Engine torque will change according to crankshaft. Horsepower Torque Speed (RPM)

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42 27. At what rpm will the engine from the power curve at the right reach: Maximum BHP: rpm Maximum Torque: rpm What is the Maximum Torque: lb ft How many Watts at 14 Ft. Lbs of Torque?

43 28. Horsepower continues to increase until engine speed is very. High Average Low

44 29. How well an engine breathes is referred to as: Mechanical Efficiency Thermal Efficiency Volumetric Efficiency

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47 30. efficiency is BHP IHP. Mechanical Thermal Practical

48 31. If the brake horsepower of an engine is 8.0 and the indicated horsepower is 9.0 the M.E. is % = 88% M.E.

49 32. efficiency rates how much of the power produced by the burning fuel is actually use to drive the piston downward and rotate the crankshaft. Mechanical Thermal Volumetric

50 33. Most small engines are only about % to % thermally efficient. 5% to 10% 20% to 25% 80% to 90%

51 34. An engine will lose about % of its heat out the exhaust & about 35% to 40% to the cooling system. 1/3 1/2 3/4

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53 35. An engine with 10HP at sea level & 70 F is taken to an altitude of 3000 & run in 90 F heat. What % of HP is lost? 1% x 3 = 3% loss 3.5% x 3 = 10.5% loss 3% % = 13.5% overall loss of HP due to conditions