Interference and TimingBy: Baha Alawi

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

Terminology

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

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

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

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)

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

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

References• http://

www.familycar.com/CarCare/TimingBelt.htm

• http://autorepair.about.com/cs/doityourself/a/aa051102a.htm

• http://www.cars.com/go/advice/Story.jsp?section=ct&subject=adv&story=ctTiming

• http://www.autoswalk.com/rubtimbelini.html

• http://www.autoclubgroup.com/michigan/autos/car_maintenance/guides/belts.asp