Thin sleeve cylinder wall construction results in a reduction of the total amount of aluminum used in the engine for a lightweight engine block. Plateau honing lowers the friction level between the pistons and the cylinders by creating an ultra smooth surface. Plateau honing is a two stage machining process that uses two grinding processes instead of the more conventional single honing process. This also enhances the long-term wear characteristics of the engine.

Low friction pistons made of aluminum alloy are lightweight and have "micro-dimples" on the cylinder walls for improved lubrication. Offset cylinder bores help minimize friction by positioning the crankshaft axis in a more efficient alignment to the cylinder bore axis. This reduces friction caused by the side thrust of the pistons against the cylinder walls, just after top-dead-center, as each piston begins its descent on the firing stroke.

Connecting rods are high strength forged steel units that have been treated with a special carbon process that hardens the surface and allows engineers to use a design that weighs less than a traditional connecting rod.

Civic Hybrid Cylinder Head: 3-Stage i-VTEC with Variable Cylinder Management (VCM)
The Civic Hybrid uses a 3-Stage i-VTEC valve control system that provides normal valve timing, high output valve timing and cylinder idling functions to the benefit of low fuel consumption, high output and greater electrical regeneration capabilities. The previous generation system in the 2005 Civic Hybrid uses 2-stage VTEC that provides normal valve timing and 3-cylinder idling. The 3-stage system adds high output valve timing and 4-cylinder idling. The high output valve timing contributes to the engines increase in output of 9 percent, while the added cylinder deactivation reduces pumping losses by 66 percent to help improve electrical regeneration capability by 1.7 times.

The Civic Hybrid's single overhead camshaft (SOHC) cylinder head uses a compact chain drive and a compact, low friction VTEC system. It uses a common rocker shaft for both the intake and exhaust rocker arms. Placing all the rocker arms on one shaft eliminates the need for a second rocker-arm shaft, so the valve mechanism can be lighter and more compact. To reduce friction, the rocker arms have rollers built-in.

The compact valvetrain allows for a desirable narrow angle (30-degrees) between the intake and exhaust valves, which helps supply a more powerful direct charge into the cylinder chamber. The narrow angle valvetrain also allows for a more compact combustion chamber. The intake ports create a swirl effect in the cylinder chamber that promote a well balanced and even air fuel mixture as it enters the engine. This optimizes the air fuel mixture for a cleaner, more efficient combustion.

The new VCM system is an advanced form of the three-cylinder Cylinder Idling System used on the previous generation. VCM allows the regenerative braking system to reclaim as much energy as possible during deceleration, while also allowing the electric motor to propel the vehicle in certain steady state cruising situations.

Since the electric motor, which also acts as an electric generator, is attached directly to the crankshaft of the engine, the engine needs to provide as little resistance as possible during deceleration to allow the generator to produce high levels of electricity and charge the batteries. In a traditional engine, the pumping action of the cylinders will actually provide a moderate amount of resistance, or "engine braking," during deceleration. VCM virtually eliminates that effect.

From a mechanical standpoint, the three stage VTEC switching capabilities are made possible a rocker arm design with three hydraulic circuits that accommodates a) low rpm VTEC switching on each cylinder's intake and exhaust valve and b) high speed switching on the [intake] valve. Three oil passages inside the rocker shaft receive oil from an external spool valve (controlled by the ECU based mostly on throttle and rpm). The oil pressure from one of the three passages activates a combination of push pins inside the rocker arms for each of the intake and exhaust valves. By moving the pins, the intake valve rocker arms can follow one of two lobes on the camshaft (normal or high profile). Or, to deactivate the valves and leave them closed, the pins are pushed in a direction that allow part of the intake and exhaust rocker arms to move with the camshaft and not move the closed valves.

Civic Hybrid: Dual & Sequential Ignition with Twin Plug Sequential Ignition Control
The twin plug sequential ignition control is part of the i-VTEC system and helps facilitate an intense and rapid combustion process in the engine. The ignition control has eight ignition coils that are independently controlled according to a dynamic engine map program. The benefits are more power, less fuel consumption and reduced emissions. Honda's patented twin plug sequential control system is programmed to respond to engine rpm and load conditions. Since the system has eight individual ignition coils, it can manipulate the ignition timing of each iridium-tipped spark plug.

When the air/fuel mixture enters the combustion chamber, the first plug located near the intake port ignites. Shortly thereafter, the second plug located near the exhaust port ignites, accelerating the combustion process by forcing the flame to more rapidly propagate. The spark plugs can also ignite simultaneously under certain circumstances. This process results in a more complete combustion compared to a single plug system.

Civic Hybrid: Drive-by-Wire Throttle Control
An electronic drive-by-wire system helps enhance the driving character of the Civic Hybrid. With smart electronics connecting the throttle pedal to the throttle butterfly valve in the intake manifold, the engine response and IMA operation can be optimized to suit the driving conditions and to better match the driver's expectations. By eliminating the direct throttle cable connection to the engine, the ratio between pedal movement and throttle butterfly movement can be continuously optimized. This adjustable "gain" between throttle and engine is a significant step forward in drivability, which also allows for VCM to cut all cylinders and drive with the electric motor only during some cruising situations. A highly responsive DC motor moves the throttle butterfly position in the intake manifold to change actual throttle position. To establish the current driving conditions, the system monitors pedal position, throttle position, vehicle speed, engine speed, calculated road slope and engine vacuum. This information is then used to define the throttle control sensitivity.

Civic Hybrid: Programmed Fuel Injection (PGM-FI)
The Civic Hybrid is equipped with a Programmed Fuel Injection (PGM-FI) system. The system monitors throttle position, engine temperature, intake-manifold pressure, atmospheric pressure, exhaust-gas oxygen content, and intake-air temperature. It controls fuel delivery by multi-holed injectors mounted in the plastic intake manifold. The ECU also tracks the operation of the engine with position sensors on the crankshaft and camshaft.

Civic Hybrid: Lightweight Composite Resin Intake Manifold Chamber
Upstream from the aluminum intake manifold, the engine's intake manifold chamber is constructed of a composite resin instead of aluminum alloy in order to save weight. The individual pieces that make up the manifold chamber are permanently connected with a vibration welding technique.

Civic Hybrid: Hybrid Dual Scroll Air Conditioning Compressor
A dual scroll hybrid air conditioning system reduces the load on the gasoline engine by using a combination of engine power and an internal electric motor to drive two air conditioning compressors. These compressors can act independently or together as dictated by the cooling needs of the Civic Hybrid's automatic climate control system.

Under normal conditions, either of the two compressors cools the interior cabin individually depending upon cooling needs and the charge state of the IMA's battery pack. On warmer days, the 75cc engine-mounted compressor acts as the sole source of air-conditioning, while the 15cc motor-driven compressor is in action when the climate control is maintaining a steady temperature or the car is idle-stopped.

Under extreme ambient conditions, cooling is provided by the 75cc belt-driven compressor attached to the engine and the 15cc, 144V motor-driven by an internal electric motor. When the air conditioning system is forced to use both the gasoline engine and electric motor, the Civic Hybrid's idle-stop feature is temporarily disabled until cooling needs are reduced.

Civic Hybrid: Engine Mounts
A new torque rod damper system added to the subframe helps reduce rocking and isolate powertrain NVH from the passenger compartment. Engine mounts, one of which is hydraulic, and reinforcements in the engine compartment help further reduce engine noise and vibrations. These features significantly reduce vibration and result in a more comfortable ride.

Source: Honda PR