Honda’s fourth-generation hybrid, the Civic
Hybrid, combines a petrol-powered engine with an electric motor to boost power
and cut fuel consumption and exhaust emissions. A Nickel-Metal Hydride (NiMH)
battery pack is used to capture and store electricity for the electric
The improved Integrated Motor Assist (IMA) system
now allows the Civic Hybrid to drive on electric power alone, provided the
vehicle is travelling at less than 40 km/h. The Civic Hybrid has a combined
petrol/electric output of 85kW and develops 170Nm. Quoted fuel consumption is
4.6 litres per 100km, a saving of 0.6 litres per 100km over the previous model.
The Civic Hybrid is equipped with a Continuously Variable Transmission
During acceleration, the engine, or the engine
working in tandem with the electric motor, propel the vehicle. During cruising,
the petrol engine and/or the electric motor can propel the vehicle, depending on
conditions. During braking, the petrol engine deactivates and the electric motor
acts as a generator to replenish the battery pack. At a stop, the engine can
enter an idle-stop mode to save fuel and reduce emissions, with the engine
turned off until the brake pedal is released.
Engine Block Construction, Pistons and
The 1.3 litre aluminium engine block and its
internal components create a lightweight package with extremely low friction
qualities. To save weight, the block incorporates a thin sleeve construction.
Friction-reducing measures include plateau honing, low friction pistons, low
tensile force piston rings and an offset cylinder bore.
Thin sleeve cylinder wall construction results in
a reduction of the total amount of aluminium used in the engine. 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 aluminium alloy are
lightweight and have “micro-dimples” on the cylinder walls for improved
lubrication. Offset cylinder bores help minimise 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-centre, as each piston begins its descent on the
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
3-Stage i-VTEC with Variable Cylinder
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. 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.
Over the previous model, the high output valve timing contributes to the
engine’s output increase 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 built-in rollers.
The compact valvetrain allows for a 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 optimises the air fuel mixture for a
cleaner, more efficient combustion.
The new VCM (Variable Cylinder Management) 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 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 by 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.
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.
Electronic Throttle Control
An electronic drive-by-wire system enhances 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 optimised 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 optimised. This adjustable
“gain” between throttle and engine is a significant step forward in
driveability, which also allows for VCM to cut all cylinders and drive with the
electric motor only during some cruising situations. A 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
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
Lightweight Composite Resin Intake Manifold
Upstream from the aluminium intake manifold, the
engine’s intake manifold chamber is constructed of a composite resin instead of
aluminium alloy in order to save weight. The individual pieces that make up the
manifold chamber are permanently connected with a vibration welding
Dual Scroll Air Conditioning Compressor
A dual scroll hybrid air conditioning system
reduces the load on the petrol 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 petrol engine
and electric motor, the Civic Hybrid’s idle-stop feature is temporarily disabled
until cooling needs are reduced.
A new torque rod damper system added to the
subframe helps reduce rocking and isolate powertrain NVH from the passenger
compartment. The engine mounts, one of which is hydraulic, and reinforcements in
the engine compartment help further reduce engine noise and vibrations.
The 4th generation IMA system is the most powerful
and most efficient to come out of Honda’s hybrid development program. (1st
generation: Insight; 2nd generation: Civic Hybrid; 3rd generation:
Accord Hybrid.) As with previous versions, the IMA system consists of an
ultra-thin DC brushless electric motor mounted between the petrol engine and the
continuously variable transmission, and an Intelligent Power Unit (IPU) that
stores electric power in a battery and controls the flow of electricity to and
from the electric motor.
IMA Electric Motor
Providing a supplemental power boost to the
1.3-litre 4-cylinder engine and giving the Civic Hybrid the capability to cruise
on its electric motor in certain situations, the IMA’s electric motor is
designed to provide up to 15 kW and 89Nm of additional torque to the Civic
Hybrid’s engine. Mounted between the engine and the CVT transmission, the IMA
motor is a 70 mm thick DC brushless design and provides a substantial amount of
low-end torque to aid acceleration, while also assisting in steady-state
cruising and hill climbing.
In addition to providing supplemental motive
power, the IMA motor acts as a generator during deceleration and braking to
recapture kinetic energy and recharge the IMA’s battery pack during regenerative
For this fourth generation of IMA motor, a new
internal permanent magnet was designed to increase output density and make the
motor more efficient than previously. It also uses flat wire construction to
increase wire density. The electric motor has increased output power by 46
percent and maximum torque by 14 percent compared with the 2005 Civic Hybrid IMA
motor. The electric motor is also more efficient, now converting 96 percent
(versus 94.6 percent efficiency of the 2005 Civic Hybrid IMA motor) of the
available electricity into motive energy in assist mode.
IMA Intelligent Power Unit (IPU)
Power for the IMA system is controlled through the
Civic Hybrid’s Intelligent Power Unit. Located directly behind the rear seat,
the IPU consists of the Power Control Unit (PCU) - the IMA’s command centre, a
rechargeable Nickel Metal-Hydride battery module, and an integrated cooling
The Power Control Unit (PCU) electronically
controls the flow of energy to and from the IMA’s electric motor. Using the
latest computer chip technology, the PCU’s response time is quicker than the
previous versions, and a new inverter and DC/DC Converter help contribute to the
IMA’s overall increase in power.
The battery pack stores electricity in a bank of
Nickel Metal-Hydride cells. This bank of 132 1.2-volt units stores up to 158
volts of electrical energy for the IMA motor compared to 144 in previous
versions. A new Panasonic dual module casing reduces weight from previous hybrid
battery packs and also allows it to increase efficiency of the electrical flow.
The 12 percent smaller battery pack provides more cargo space.
The Integrated Cooling Unit offsets the heat
generated by the constant flow of electricity to and from the battery pack with
an integrated cooling system mounted directly on the battery pack’s outer box.
Interior cabin air is continually flowed over the battery pack and re-circulated
via a small vent placed on the rear seat shelf.
Cooperative Regenerative Brake System
Hybrid-powered vehicles recapture kinetic energy
via regenerative braking and store this energy as electricity in rechargeable
battery packs. The Civic Hybrid is no different, as its IMA electric motor also
acts as a generator that can recharge its battery pack during braking, steady
cruising, gentle deceleration, or coasting. New for 2006, a cooperative
regenerative braking system debuts on the Civic Hybrid with the added capability
to intelligently proportion braking power between the hydraulic brakes and the
electric motor to extract even more electricity from the vehicle’s kinetic
energy. Less reliance on the traditional braking system and reduced engine
pumping losses translate into greater electrical regeneration (170 percent more
than the 2005 Civic Hybrid) and ultimately improved fuel economy.
When braking, a brake pedal sensor sends a signal
to the vehicle’s IMA computer (IPU). The computer activates a servo unit in the
brake system’s master cylinder that proportions braking power between the
traditional hydraulic brakes and the electric motor to maximised regeneration.
Previous versions of Honda’s IMA systems proportioned braking power at a pre-set
rate below the maximum regeneration threshold and with no variable
Continuously Variable Transmission
Honda’s Continuously Variable Transmission (CVT)
is standard equipment on the Civic Hybrid and provides a 9 percent wider range
between the maximum and minimum gear ratios to enhance acceleration and minimise
engine rpm at high speeds.
Unlike a conventional transmission with four of
five gears that change the final drive ratio in steps, a CVT uses a steel belt
and a variable pulley to infinitely change the final drive ratio between a
minimum and maximum setting. The variable pulley with its angled internal sides
moves in and out by hydraulic pressure to expand or reduce the radius travelled
by the steel belt.
Improvements to the new CVT include:
9 percent wider ratio range of 2.52 - 0.421:1
(previously 2.36 - 0.407:1)
Final drive ratio of 4.94:1 (previously
Expanded pulley axial distance from 143 mm to 156
Expanded pulley ratio range to 6.0 mm from 5.8
Double hydraulic piston used on variable pulley
increases pressure by 170 percent
Improved low friction construction for overall
Torque handling capacity increases by 18
Overall, a CVT provides a greater fuel economy
benefit than a conventional automatic transmission with gears. It helps the
engine stay in its most efficient operating range for both performance and
economy, and the need to shift gears is eliminated.
2006 Civic Hybrid Specifications
Wheelbase (mm) - 2700
Length (mm) - 4550
Width (mm) - 1750
Height (mm) - 1430
Engine - 1.3-litre i-VTEC SOHC
Power @ rpm (combined) - 85 @ 6000
Torque (Nm) @ rpm (combined) - 170 @ 2500
Transmission - CVT
Tyre Size - 195/65 R15
Fuel consumption (litres per 100km) - 4.6
Weight - 1265
Next week: we road test the Honda Civic