Interference and Timing By: Baha Alawi

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Interference and TimingBy Baha Alawi

• Objective Explain the purpose and consequences
  of using a timing belt in an interference and
  non-interference engine

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Terminology
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Timing Belt

• Car manufactures use rubber belts instead of
  chain because of noise and cost
• Purpose is to provide a quiet, flexible
  connection between the camshaft and crankshaft to
  keep the valves opening and closing in phase with
  the movement of the pistons
• Without a timing belt, engine will not run

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Turning Ratios

• Timing belt turns the Camshafts at exactly 1/2
  the speed of the Crankshaft while maintaining a
  precise alignment
• Crankshaft will make two revolutions for every
  revolution of the camshaft

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Interference Engines

• If the timing belt slips or breaks, the piston
  can crash into an open valve causing serious
  internal engine damage by bending valves and
  breaking pistons
• Repair price is catastrophic or new engine
  installment

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Non-Interference Engines

• Not self destructive
• If the belt fails, there is enough clearance
  between the pistons and valves to prevent
  damaging contact
• Engine will immediately shuts down leaving you
  stranded (inconvenient)

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Why choose a car with an interference engine?

• Valves open more in the combustion chamber
  allowing more air to flow in
• When engine inhales more air, it can burn more
  fuel resulting in more power output

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Warning

• Breakage is not the only reason to replace your
  timing belt. Looseness and wear will allow the
  timing belt to slip and change valve timing
  resulting in very poor performance or engine
  damage
• Timing belts have a limited life expectancy,
  perform visual inspections for signs of wearing
  and change it at the recommended time interval

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References

• http//www.familycar.com/CarCare/TimingBelt.htm
• http//autorepair.about.com/cs/doityourself/a/aa05
  1102a.htm
• http//www.cars.com/go/advice/Story.jsp?sectionct
  subjectadvstoryctTiming
• http//www.autoswalk.com/rubtimbelini.html
• http//www.autoclubgroup.com/michigan/autos/car_ma
  intenance/guides/belts.asp