The Civic Hatchback's 1.5-liter inline four has a lightweight die-cast aluminum block with individual reinforced main bearing caps to minimize weight. Cast-in iron cylinder liners provide long-lasting durability. Each journal on the lightweight forged-steel crankshaft is micropolished to reduce internal friction.
Pistons and Connecting Rods
The 1.5-liter engine's pistons have "cavity-shaped" crowns that help maintain stable combustion and contribute to improved efficiency. The lightweight pistons have a carefully optimized skirt design to minimize reciprocating weight, which minimizes vibration and increases operating efficiency. The pistons are cooled by twin oil jets directed at the underside of each piston crown. Ion-plated piston rings help reduce friction for greater operating efficiency. Lightweight, high-strength steel connecting rods are heat-forged in one piece and then "crack separated" to create a lighter and stronger rod with an optimally fitted bearing cap.
Cylinder Head and Valvetrain
The direct-injected Civic Hatchback 4-cylinder turbocharged engine has a lightweight pressure-cast aluminum alloy DOHC cylinder head. With exhaust ports cast directly into the cylinder head, the need for a traditional separate exhaust manifold is eliminated, reducing engine weight and simplifying the assembly.
A low-friction, silent-chain drives dual overhead cams and four valves per cylinder. The cam drive is maintenance free throughout the life of the engine. To help further reduce weight, new thin-wall hollow camshafts are used.
To benefit fuel efficiency, emissions and power, the turbo engine utilizes sodium-filled exhaust valves. A hollow chamber within the valve contains sodium that is cooled by the exhaust port cooling jacket. As the chamber reaches close to the valve head, the sodium helps to cool the entire valve. Since the valve is internally cooled it doesn't need the enriched fuel mixture that is generally used in turbo engines to help cool the exhaust valve. The resultant leaner mixture reduces emissions, increases fuel efficiency and helps increase power.
The cylinder head includes small M12 sparkplugs, down from the more common M14, to save space and weight. The head also includes direct-injection multi-hole fuel injectors with a small-diameter bore. Higher-pressure direct injection optimizes fuel atomization, allowing for more efficient combustion. To provide a high-tumble intake charge that further enhances combustion efficiency, both the intake port and piston crown have special designs.
The Civic Hatchback turbo engine features Variable Valve Timing Control (VTC) that can vary the timing of both the intake and exhaust camshafts independently to best suit the driving conditions. Under light loads, valve overlap can be increased to reduce pumping losses and improve fuel efficiency. When engine speed is low and engine load is large, such as during initial acceleration, the amount of overlap is increased to boost the scavenging effect, which improves torque and responsiveness. When engine speed is high and engine load is also high, such as during full-throttle acceleration, the amount of valve overlap is reduced to increase engine output by improving both intake and scavenging.
Direct Injection System
The direct-injection system enables increased torque across the engine's full operating range along with higher fuel efficiency and low emissions. Multi-hole injectors deliver fuel directly into each cylinder (not to the intake port, as in conventional port fuel injection designs), allowing for more efficient combustion. The system features a compact, high-pressure, direct-injection pump that allows both high fuel flow and pulsation suppression, while variable pressure control optimizes injector operation.
Low Inertia Mono Scroll Turbo System with Electric Wastegate
The turbocharged Civic engine employs a small-diameter, low-mass turbine for maximum responsiveness. The Mono scroll housing design helps the turbo build boost even at relatively small throttle openings and low rpm. The electrically actuated wastegate allows boost pressure to be precisely controlled.