Honda Automobiles / Accord
2014 Honda Accord Hybrid: Powertrain
For the ninth-generation Accord, Honda offers the widest range of power trains in the model's history. Two Earth Dreams Technology™ engines were initially available in the completely redesigned 2013 Accord family - an all-new direct-injected (DI) 2.4-liter inline 4-cylinder engine, and a significantly updated 3.5-liter V-6 with Variable Cylinder Management (VCM). (Please see the 2013 Honda Accord Press Kit for more information.) Then, in early 2013, the all-new 2014 Honda Accord Plug-in Hybrid (PHEV) Sedan with an Earth Dreams Technology™ 2.0-liter 4-cylinder/two-motor plug-in hybrid powertrain also joined the lineup.
The Accord Plug-In Hybrid and the Accord Hybrid have a completely new hybrid system for midsize vehicles that is an altogether different hybrid from Honda's Integrated Motor Assist (IMA) system. The Accord Plug-In Hybrid and the Accord Hybrid have a new system called Intelligent Multi-Mode Drive (i-MMD). Under most conditions the gas engine powers a generator, which in turn provides energy to charge the hybrid battery and/or for the electric motor to drive the wheels. In addition, the i-MMD can operate on gasoline engine power only, mainly during medium- to high-speed cruising.
Honda's i-MMD uses a new two-motor hybrid approach that continuously cycles between three different modes - EV drive, hybrid drive and engine drive - to maximize fuel efficiency. The key difference between the Accord Plug-In and Accord Hybrid is the size of the onboard battery, and the presence of an onboard charging system and cord in the case of the Plug-in Hybrid. The Accord Plug-in Hybrid (PHEV) uses a 6.7 kilowatt-hour lithium-ion battery and charging cord that allows recharging in less than three hours using a 120-volt outlet and less than one hour using a Level-2 (240-volt) charger.
The new Accord Hybrid is a non plug-in vehicle, and has a smaller, more compact 1.3 kilowatt-hour (kWh) lithium-ion battery that is charged via the vehicle's 2.0-liter gasoline engine, regenerative braking, or a combination of the two. The result of the Accord Hybrid's cutting-edge powertrain technology is a fun-to-drive character, coupled with anunmatched city fuel-economy rating. The Accord Hybrid has EPA fuel economy ratings of 50/45/47 mpg city/highway/combined 2 that gives it the best-in-class city rating for four door sedans, and ties it for best-in-class in the combined rating.
(For more detail on Accord engine features, please see the 2013 Accord Press Kit.)
2.0-liter inline-4 Hybrid (FHEV Sedan) Features
- 2.0-liter, DOHC, i-VTEC® inline-four
- Maintenance-free 124-kW electric motor
- 1.3 kWh Li-Ion battery
- Electric-servo braking system
- i-VTEC® (Variable Valve Timing and Lift Electronic Control) + Electric VTC
- Regular unleaded fuel
- Drive-by-Wire Throttle System™
- Electric Continuously Variable Transmission (E-CVT)
- Close-coupled catalytic converter plus under-floor catalytic converter
- 100,000+/- miles engine tune-up interval
- Eight-year/100,000-mile or ten-year/150,000 mile Li-Ion battery limited warranty, depending on the state of purchase/registration.
- 24-hour roadside assistance (during initial warranty period)
High-efficiency Earth Dreams Technology™ Two-Motor Hybrid System
Honda's hybrid technology has progressed substantially since the introduction of the first gas-electric hybrid to the U.S. market in 1999, Honda's original Insight. Today, the Accord Hybrid is a standard-bearer of Honda's environmental leadership efforts.
The Accord Hybrid's i-MMD system is a highly efficient powertrain that selects the optimal drive mode under a wide range of driving conditions to combine a fun-to-drive character with excellent fuel efficiency. Detailed energy management for each component enables this system to make the best use of both the electric propulsion motor and the gasoline engine to seamlessly provide smooth and responsive performance and a best-in-class (four door sedan) city fuel-economy rating.
To help maximize efficiency on the road, the Accord Hybrid seamlessly shifts between three distinct drive modes: EV Drive (100 percent electric motor), Hybrid Drive (electric motor and gasoline engine [driving the generator motor]) and Engine Drive (gasoline engine). The Accord Hybrid's powertrain shifts seamlessly and smoothly among the three driving modes, utilizing power from the i-VTEC® 4-cylinder engine and the electric motor to suit the driving conditions moment to moment.
EV Drive Mode
All-electric drive EV Drive Mode is active when starting from a stop, during light cruising and acceleration, and when braking. The gasoline engine is off in this mode and is decoupled from the drivetrain to reduce friction.
Hybrid Drive Mode
The electric motor and gasoline engine work together when accelerating and at higher speeds. The electric propulsion motor alone powers the front wheels, as the gasoline engine (decoupled from the drive wheels) powers the electric-generator motor, which in turn provides power to the battery pack. This allows the gas engine-generator motor combo to supplement the battery by providing added electrical power to the propulsion motor or, alternatively, to charge the battery. The electric propulsion motor offers crisp acceleration, and can reach maximum torque almost instantaneously, thanks to electrical power that can be supplied from both the gas engine-powered motor/generator and the battery.
Engine Drive Mode
When cruising at medium to high speeds, the high-efficiency Atkinson-cycle i-VTEC gasoline engine provides propulsion via the E-CVT with lock-up clutch, which connects the generator motor (always linked to the engine) and the electric drive motor, effectively sending motive power directly from the engine to the drive wheels..
2.0-liter Inline 4-cylinder Atkinson Cycle Engine An all-new 2.0-liter DOHC i-VTEC 4-cylinder Atkinson Cycle engine that develops a peak 141 horsepower and 122 lb-ft. of torque powers both the Accord Hybrid and the Accord Plug-in Hybrid. It is one of the world’s most thermally efficient powerplants and is a key part of Honda’s expanding Earth Dreams Technology™ powertrain lineup, which is comprised of a next-generation set of technological advancements that greatly enhance both driving performance and fuel efficiency. In fact, at 214 g/kWh of 87-octane gasoline fuel, this engine is the most energy efficient mass produced gasoline internal combustion engine available in the world, based on internal testing.
The engine’s Atkinson Cycle design and other technologies combine to create excellent power characteristics, exceptional fuel efficiency and very low exhaust emissions. This clean-running engine meets LEV3- AT-PZEV(SULEV30)/ BIN3 emission standards. The gasoline engine produces a maximum 141 horsepower at 6200 rpm; while the Accord Hybrid’s total system output (peak horsepower of both the gas engine and the two-motor hybrid-drive system) is 196 hp. The Accord Hybrid Sedan has an EPA fuel-economy rating of 50/45/47 mpg city/hwy/combined.2
Since the gasoline engine can be decoupled from the rest of the hybrid powertrain, it only operates as needed. Depending on the state of battery charge and other parameters, it will automatically shut off during deceleration and when the vehicle is at a stop or operating under battery power. When needed, the gasoline engine restarts automatically, without action from the driver.
Engine Block, Crankshaft and Pistons
The engine has a displacement of 1993cc. Cast-in iron cylinder liners provide long-lasting durability. Each journal on the forged-steel crankshaft is micro-polished to reduce internal friction. To improve smoothness throughout the rpm range and help lower noise levels, the Accord Hybrid is fitted with an internal balancer unit. Consisting of a pair of chain-driven counter-rotating shafts located in the oil pan, the balancing system helps quell the inherent second-order harmonic vibrations that are normally associated with inline 4-cylinder engines.
Like the 2.4-liter engine that powers the non-hybrid Accord Sedan and Coupe, the 2.0-liter hybrid engine has cylinder bores offset by 8.0 mm from the crankshaft to help reduce piston-sliding friction. This gives the connecting rods a more favorable angle during each power stroke, which reduces side loading on the pistons and, in turn, improves efficiency.
The lightweight pistons have a carefully optimized skirt design to minimize reciprocating weight, and reduced weight minimizes vibration and increases operating efficiency.
Cylinder Head and Valvetrain
The Accord Hybrid 4-cylinder engine has a lightweight cylinder head that is made of pressure-cast aluminum alloy. A 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 boost fuel efficiency and power, the engine has a 3.4-degree included angle between the intake and exhaust valves. The narrow valve angle decreases the surface-to-volume ratio and helps create a flatter, more compact combustion chamber that reduces unburned hydrocarbon emissions. This combustion chamber shape and the precise control allows the compression ratio to be a high 13.0:1 (up from 11.0:1 on the 2.4-liter non-hybrid Accord engine), yet the engine still operates on regular unleaded fuel.
i-VTEC Valve Control System
The Accord Hybrid's 2.0-liter DOHC 16-valve i-VTEC engine uses an advanced valve-control system to combine high power output with high fuel efficiency and low emissions. The system combines E-VTC (Electronic Variable Timing Control), which continuously adjusts the intake camshaft phase, with Variable Valve Timing and Lift Electronic Control (VTEC), which changes the lift profile, timing and duration of the intake valves' operation.
High-Efficiency Catalytic Converters
Key contributors to the Accord 4-cylinder engine's excellent emissions performance are its dual high-efficiency catalytic converters. One converter mounts directly to the front of the cylinder head, close-coupled for fast activation after the engine is started. A second converter is positioned slightly downstream, beneath the passenger compartment floor. Both converters use a thin-wall design that increases internal reaction area and improves efficiency. A high-efficiency exhaust system and high-density catalytic converters help the Accord engine meet stringent LEV3- AT-PZEV(SULEV30)/ BIN3 standards, which require reduced greenhouse gases compared to lower standards.
The Accord Hybrid (like the Accord Plug-in Hybrid) uses two electric motors. The 124 kW AC synchronous permanent-magnet propulsion motor, linked to the drive wheels, provides primary motive power for the vehicle. When in regenerative mode, the propulsion motor converts the kinetic energy of the decelerating vehicle into electrical energy to recharge the battery. Its operation is seamlessly coordinated with the Accord Hybrid's electric-servo braking system. (See Chassis section for more information.) A separate generator motor is driven by the gasoline engine to generate electric energy to drive the propulsion motor when the vehicle is operating in Hybrid Drive Mode. This generator motor can also restart the gasoline engine when the vehicle is in idle-stop mode.
Lithium-Ion Hybrid Battery
- The Accord Hybrid's integrated Power unit (IPU), located behind the rear seat, packages a 1.3 kWh Li-Ion battery and a DC-DC converter. The Li-Ion battery type offers high energy density, allowing the compact and lightweight battery to be positioned behind the Accord Hybrid's fixed rear seatback. Battery temperature is controlled by a fan system that pulls air from the interior of the vehicle via vents on the driver's side of the rear seatback. The battery powers the Accord Hybrid's electric propulsion motor. It is recharged by the propulsion motor operating in regenerative braking mode, and by the generator motor, which is powered by the gasoline engine. The battery pack is covered by a special warranty that covers defects in material and workmanship for eight-years/100,000-miles or ten-year/150,000 miles depending on the state of purchase/registration.
Electric Continuously Variable Transmission (E-CVT)
The Accord Hybrid is not equipped with a conventional physical transmission. Instead, the Electric Continuously Variable Transmission (E-CVT) consists of the interaction of the Accord Hybrid's gasoline engine and two electric motors. Coordinated by the IPU, the E-CVT offers smooth and predictable acceleration matched with efficient low-rpm highway cruising when the gasoline engine is in operation. Gasoline engine shutdown is seamlessly integrated into the operation of the Accord Hybrid when appropriate.
The E-CVT system, unlike other full hybrid systems, operates without the need for a torque converter, mechanical pulley or belt. It instead uses two motors for driving and generating power. Unlike a conventional CVT, E-CVT is optimally and rapidly able to control both engine and electric motor rotation in order to deliver higher fuel efficiency and quicker engine response in each driving mode.
When cruising at mid- or high-speeds in the high-efficiency range of the engine, the lock-up clutch built into the E-CVT is engaged, connecting the drive motor to the generator motor to transmit engine torque directly to the drive wheels as efficiently as possible. In EV Drive mode, when the battery-powered drive motor is used for either acceleration or regenerative braking, a clutch disengages the stopped gasoline engine from the drivetrain to eliminate efficiency loss from mechanical friction in the engine.
E-CVT Automatic Modes
The transmission, with its console-mounted straight-gate shifter, can be operated in two different fully automatic modes. The D mode is ideal for most driving situations, and combines fuel efficiency with smooth operation and responsive power when needed. The B (Brake) mode offers substantially increased regenerative braking.
Immediately behind the shifter is an EV button that lets the driver select purely electric operation. A green EV icon lights on the instrument panel in this mode. When the battery charge is sufficiently depleted, EV Mode is automatically cancelled and the gasoline engine will automatically restart to recharge the battery in Hybrid Drive Mode or Engine Mode.
Electric Engine Accessories
The Accord Hybrid's engine accessories operate electrically, both for maximum efficiency and to allow their operation whether the gasoline engine is running or not. The air conditioning compressor and water pump are both powered by the electrical system. In addition, the Accord Hybrid has Electric Power Steering (EPS), which eliminates the traditional hydraulic power steering pump and its associated maintenance and energy costs. (See Chassis section for more information.)