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Bike Basics


Some form of pressure is ... a value that represents the ratio of the volume of its ... engine power measurement Watt determined that a horse ... – PowerPoint PPT presentation

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Title: Bike Basics

Bike Basics
What will we see today?
  • A typical spec sheet
  • Engine What is it?
  • Types of Engines
  • Two Stroke
  • Four Stroke
  • Wankel/Rotary
  • Displacement Calculation
  • What is Power

Spec Sheet
  • Engine Components Typical Four Stroke Motor
  • Head
  • Cams
  • Camshaft
  • Valves
  • Buckets
  • Block
  • Piston
  • Piston Rings
  • Con Rod
  • Crankcase
  • Crankshaft
  • Bearings

  • Typical working of an engine
  • Intake
  • Air Fuel Compression charge
  • Ignition
  • Expansion due to ignition
  • Reciprocating to Rotary Motion

Typical Two Stroke Motor
  • This system manages to pack one power stroke into
    every two strokes of the piston (up-down). This
    is achieved by exhausting and re-charging the
    cylinder simultaneously.
  • The steps involved here are
  • Intake and exhaust occur at bottom dead center.
    Some form of pressure is needed, either crankcase
    compression or super-charging.
  • Compression stroke Fuel-air mix compressed and
  • Power stroke piston is pushed downwards by the
    hot exhaust gases.

Typical Two Stroke Motor
Typical Four Stroke Motor
  • Engines based on the four-stroke ("Otto cycle")
    have one power stroke for every four strokes
    (up-down-up-down) and employ spark plug ignition.
    Combustion occurs rapidly, and during combustion
    the volume varies little ("constant volume
  • The steps involved here are
  • Intake stroke Air and vaporized fuel are drawn
  • Compression stroke Fuel vapor and air are
    compressed and ignited.
  • Combustion stroke Fuel combusts and piston is
    pushed downwards.
  • Exhaust stroke Exhaust is driven out.

Typical Four Stroke Motor
What is Displacement. How to calculate the CC of
an engine
Here, Bore is the diameter measurement of the
cylinders in a piston engine Stroke refers to the
distance the piston travels between BDC and TDC
  • Lets calculate the CC ourselves
  • Pulsar 220 DTS-I
  • Bore 67 mm
  • Stroke 62.4 mm
  • Displacement (3.1415/4) (6.7 6.7) (6.24)
  • NOTE 67 mm has been converted to cm by
    dividing it by 10. Same for Stroke
  • Displacement 219.99421 220 CC (cubic

Types of engines
  • Perfectly Square - equal bore and stroke
    dimensions, giving a bore/stroke value of exactly
  • Example Bugatti Veyron
  • Oversquare or Short Stroke - bore is larger than
    stroke, giving a bore/stroke value of greater
    than 1.
  • Allows for larger/more valves.
  • Lower Friction Losses (less piston travel)
  • High engine speeds.
  • Example Formula 1 and MotoGP engines.
  • Undersquare or Long Stroke bore is smaller than
    stroke, resulting in bore/stroke value of less
    than 1.
  • More compact
  • Higher Friction Losses
  • Typically tuned to make torque at lower engine
  • Example Enfield Bullet

  • What is Compression Ratio
  • The compression ratio of an internal-combustion
    engine is a value that represents the ratio of
    the volume of its combustion chamber from its
    largest capacity to its smallest capacity. For
    example, the compression ratio of a Bajaj Pulsar
    220 DTS-I is 12.81
  • The ratio is calculated by the following formula
  • where
  • b cylinder bore (diameter)
  • s piston stroke length
  • Vc clearance volume. It is the volume of the
    combustion chamber (including head gasket). This
    is the minimum volume of the space at the end of
    the compression stroke, i.e. when the piston
    reaches top dead center (TDC). Because of the
    complex shape of this space, it is usually
    measured directly rather than calculated.

What is Power?
  • James Watt pioneered engine power measurement
  • Watt determined that a horse could turn a mill
    wheel 144 times in an hour (or 2.4 times a
  • The wheel was 12 feet in radius, therefore the
    horse travelled 2.4 2p 12 feet in one minute
  • Watt judged that the horse could pull with a
    force of 180 pounds
  • This was rounded off to 33,000
  • Brake horsepower (bhp) is the measure of an
    engine's horsepower without the loss in power
    caused by the gearbox, alternator, differential,
    water pump, and other auxiliary components such
    as power steering pump, muffled exhaust system,

Power and Torque explained
  • Torque A simplified way of looking at torque is
    to say it is the amount of force from the engine
    that turns the rear wheel in a turning motion.
  • Power Is the rate of doing work. Normally can be
    calculated from the torque and RPM.

Typical 150cc Indian Bikes
Bike R15 Pulsar 150 FZ 16 Discover 150 RTR 160 Unicorn Average
Displacement 149.8 149.01 153 144.8 159.7 149.1 150.9
Peak Power 17 15.04 14 12.8 15.2 13.3 14.55
Peak Power RPM 8500 8500 7500 7500 8500 8000 8083
Peak Torque 15 12.7 13.6 12.7 13.1 13 13.35
Peak Torque RPM 7500 6500 6000 5500 6000 5500 6166
Weight 131 143 126 121 136 146 133
PowerWeight Ratio 129 105 111 105 111 91 108
What Next?
  • Cooling Systems
  • Clutches
  • Gearboxes