2007 Honda Civic Hybrid

Powertrain

The Civic Hybrid has a new 1.4-litre i-DSI petrol engine that works with a new, highly-efficient electric motor system to deliver economical motoring with low emissions.

Engine

The i-DSI petrol engine uses three stage i-VTEC valve control to achieve a combination of responsive driving and fuel economy. The valves are controlled by three hydraulic pathways, which couple and uncouple five rocker arm assemblies.

The really clever bit happens during deceleration, when the engine’s cylinders have their feet up. During this idle time, combustion in all four cylinders is stopped and each pot is sealed shut. This means the engine is not working as hard to pump fuel or air, so it’s immediately more efficient.

Not only that, but while the car is slowing down, the Civic Hybrid’s electric motor recovers energy generated through braking and uses it to charge the on-board battery. And as the 2006 car is more efficient than ever, it records a 10 per cent improvement in recovery of braking energy compared to the current Civic IMA, where only three cylinders are shut during idle.

The technology used to shut the cylinders, VCM (which stands for Variable Cylinder Management), is also used to shut all four cylinders when only little torque is required – during low speed cruising for example. In this mode the Hybrid is powered by the electric motor only, with the pistons running idle.

In addition, virtually everything possible has been done to the engine to reduce friction, including the use of aluminium die-cast pistons (which feature low thermal expansion for less friction under high-temperature conditions), ion-plated piston rings, and plateau honing of the cylinder walls for a smoother surface.

The engine features Honda’s i-DSI (intelligent Dual and Sequential Ignition) system that uses two spark plugs per cylinder and allows for more complete combustion of the fuel by firing the two spark plugs either at the same time or sequentially, depending on the driving conditions.

Electric motor

An all-new independently-developed electric motor uses coils with high-density windings and high-performance magnets to produce an output one and a half times that of the outgoing model – but without being any bigger. A Honda inverter is used to control motor speed, and is integrated with the motor’s ECU for more precise digital control, contributing to even greater motor efficiency and fuel economy.

Battery output has been increased by around 30 per cent over the current model, while a more compact, purpose-built battery storage box offers increased cooling performance and vibration resistance for improved long-term reliability.

The air conditioning system features a hybrid compressor that is powered by both the engine and the motor. When the engine is in ‘Idle Stop’ mode the compressor is powered by the motor; if rapid cooling is required it is powered by the engine and motor combined. When the temperature is stable it runs off the motor alone, for both improved comfort and fuel savings.

Transmission

A continuously variable transmission (CVT) is standard equipment on the Civic Hybrid. The newly-designed unit provides a wider range between the maximum and minimum gear ratios to enhance acceleration and minimise engine rpm at high speeds. The transmission provides smooth and predictable transitions and helps keep the IMA system operating at its peak efficiency.

The new CVT ’box also features unique cornering control technology to help improve response on the exit of a bend. G-Shift Control is another Honda development to improve the driving experience and increase safety levels.

When the car enters a corner, an on-board computer first identifies the vehicle’s overall speed, and then calculates the difference in speed between the left and right rear wheels. It uses this information to work out the car’s lateral G force (or the forces pushing the car ‘sideways’). The Civic Hybrid’s computer then uses the lateral G and speed information to maintain the rpm (rotation) of the petrol engine through the bend, thus allowing a higher level of torque to be available when the driver comes back on the throttle.

The fact that the rpm does not ‘drop off’ after throttle lift-off means that the car is far more responsive when exiting the corner, and there is minimum delay in the torque being fed to the wheels.

Design

Driving and safety