Toyota AR engine

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The AR engine family is an inline-4 piston engine series by Toyota, first introduced in 2008 for the RAV4, and subsequently for the Highlander, Venza, Camry and Scion tC. All AR engines feature timing chains rather than timing belts. The AR series uses a die-cast aluminium engine block and aluminium DOHC cylinder head. The engine series shares many of the technologies in the AZ engine, while incorporating features such as variable valve timing on both intake and exhaust camshafts or dual VVT-i, low friction technologies including an offset crankshaft, roller rockers for the valvetrain, a three-stage variable oil pump, reduced-tension piston rings and auxiliary belt drive. An Acoustic Control Induction System switches the length of the intake tract in two stages, based on rpm and throttle angle, thereby ensuring strong torque across a broad engine speed range. New tumble control valves enhance combustion while the engine is cold, and help to bring the catalytic converters up to working temperature quickly. The Tumble control valves, along with new 12-hole high atomizing long-nozzle fuel injectors, reduce the amount of fuel adhering to the intake ports and therefore maximize fuel economy and reduce harmful emissions. The cylinder block is an open-deck, midi-skirt type with cast-in iron liners and a die-cast aluminium lower crankcase and a stamped oil pan. The forged steel crankshaft is fully balanced with eight counterweights and supported by five main bearings. A helical gear pressed in No. 3 counterweight drives twin contra-rotating balance shafts in the shaft housing within the lower crankcase. The AR engine replaces the AZ engine.