Subaru EX35 and EX40 Engines: A Technical Overview
Introduction
The Subaru EX35 and EX40 engines are compact, high-performance boxer engines that have been used in a wide variety of Subaru vehicles since their introduction in 2006. These engines are known for their smooth, linear power delivery, excellent fuel economy, and low emissions.
Design and Construction
The EX35 and EX40 engines are both 2.5-liter naturally aspirated boxer engines. The term "boxer" refers to the unique configuration of the engine, in which the cylinders are arranged horizontally opposed to each other. This design results in a lower center of gravity, which helps to improve handling and stability.
The engines feature a lightweight aluminum block and heads with a closed-deck design for increased strength and durability. The crankshaft is forged steel, and the connecting rods are forged aluminum. The pistons are lightweight aluminum with a special coating to reduce friction.
Valve Train
The EX35 and EX40 engines use a single overhead camshaft (SOHC) design with four valves per cylinder. The camshaft is driven by a timing belt. The valve train features variable valve timing (VVT) on the intake and exhaust valves, which helps to optimize engine performance at all rpms.
Fuel System
The EX35 and EX40 engines use a multi-port fuel injection system. The fuel injectors are located directly above the intake valves, which helps to ensure efficient combustion. The fuel system is controlled by an electronic control unit (ECU), which monitors a variety of engine parameters to optimize fuel delivery.
Ignition System
The EX35 and EX40 engines use a distributorless ignition system. The ignition coils are mounted directly on the spark plugs, which eliminates the need for spark plug wires. The ignition system is controlled by the ECU, which monitors engine speed and load to optimize spark timing.
Cooling System
The EX35 and EX40 engines use a liquid-cooled cooling system. The coolant is circulated through the engine block and heads by a water pump. The coolant is then cooled by a radiator, which is mounted in front of the engine.
Lubrication System
The EX35 and EX40 engines use a wet sump lubrication system. The oil is stored in an oil pan at the bottom of the engine. The oil is then pumped through the engine by an oil pump. The oil lubricates all of the moving parts of the engine, including the crankshaft, camshaft, and pistons.
Conclusion
The Subaru EX35 and EX40 engines are compact, high-performance boxer engines that offer excellent fuel economy, low emissions, and smooth, linear power delivery. These engines are used in a wide variety of Subaru vehicles, including the Impreza, Legacy, Outback, and Forester.
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Subaru Engines EX35 and EX40 Technician / Service Manual
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EX35
EX40
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