Honda Automobiles: 2017 Honda Accord Hybrid Press Kit

Offering a significant powertrain upgrade from the previous Accord Hybrid, the 2017 model features the second-generation Intelligent Multi-Mode Drive (i-MMD) two-motor hybrid powertrain. This sophisticated, refined and seamlessly operating system further extends the Accord Hybrid’s advantages over its competitors with even more power and fuel efficiency.

Honda’s second-generation i-MMD uses a two-motor hybrid approach with three operating modes – EV Drive, Hybrid Drive and Engine Drive – responding to the demands of the driver while maximizing fuel efficiency. Under most conditions, the vehicle operates in Hybrid Drive mode, in which the gasoline engine operates as a generator, supplying electric power to the hybrid batteries, with motive power supplied by the electric propulsion motor.  Under certain conditions, the Accord Hybrid can operate on electric power only, with the engine shut off. In Engine Drive Mode, used mainly during medium- to high-speed cruising, the vehicle can operate on gasoline engine power only.

Changes to the two-motor i-MMD for the 2017 Accord Hybrid include upgrades to the gasoline engine, electric generator, electric motor, Power Control Unit (PCU), Intelligent Power Unit (IPU) and lock-up clutch. These second-generation refinements reduce weight, size and complexity, and increase power and efficiency, all of which have packaging and performance benefits. Furthermore, to enhance the fun factor, the i-MMD includes a new Sport mode.

The result of the 2017 Accord Hybrid’s cutting-edge powertrain technology is a fun-to-drive character, aided by a new Sport mode and an 8.2 percent increase in total system power to 212 horsepower (as measured by the peak, concurrent output of the two electric motors and gas engine), coupled with fuel efficiency unmatched in its segment. The Accord Hybrid has EPA fuel economy ratings of 49/47/48 mpg (city/highway/combined) – giving it by far the best-in-class ratings for midsize hybrid sedans. These EPA fuel economy ratings are based on new, more stringent ratings requirements enacted by the U.S. EPA for the 2017 model year.

Two-Motor Intelligent Multi-Mode Drive (i-MMD) Hybrid System Features

Engine

  1. 2.0-liter, DOHC, i-VTEC® inline-four
  2. Gasoline engine output: 107 kW (up from 105 kW)
  3. i-VTEC® (Variable Valve Timing and Lift Electronic Control) + Electric VTC
  4. Regular unleaded fuel
  5. Drive-by-Wire Throttle System™
  6. Close-coupled dual bed catalytic converter
  7. 100,000+/- miles engine tune-up interval

Transmission

  1. Electric Continuously Variable Transmission (E-CVT) 
  2. Maintenance-free Electric motor output: 135-kW (up from 124 kW)

Battery

  1. 1.3 kWh Li-Ion battery
  2. Eight-year/100,000-mile or ten-year/150,000 mile Li-Ion battery limited warranty, depending on the state of purchase/registration.

Others

  1. Electric-servo braking system
  2. 24-hour roadside assistance (during initial warranty period)  

Second-Generation Intelligent Multi-Mode Drive (i-MMD) Two-Motor Hybrid System
The 2017 Accord Hybrid’s second-generation i-MMD two-motor hybrid system is a highly efficient powertrain that selects the optimal drive operation under a wide range of driving conditions to combine a fun-to-drive character with excellent fuel efficiency. Detailed energy management for each component, as controlled by the Power Control Unit (PCU), 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 to garner top EPA fuel economy ratings in the midsize hybrid sedan class.

To help maximize efficiency on the road, the Accord Hybrid seamlessly shifts between three distinct drive operations: 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 operations, utilizing power from the Atkinson-cycle i-VTEC® 4-cylinder engine and the electric motor to suit the driving conditions moment to moment. An animated visual display of current operation power flow, including regeneration, can be displayed on the Multi-Information Display (MID) in the center of the instrument cluster.

EV Drive Operation
All-electric drive EV Drive operation occurs when starting from a stop, during light cruising and acceleration, and when braking. The gasoline engine is off when the i-MMD is in EV Drive mode and is decoupled from the drivetrain to reduce friction.

Hybrid Drive Operation
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. In this type of operation the system works as a “series hybrid.” 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 Operation
When cruising at medium to high speeds, the high-efficiency Atkinson-cycle i-VTEC gasoline engine provides propulsion via a new higher capacity 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. In this type of operation the system works as a “parallel hybrid” where both the gasoline engine and, when required – for instance upon quick acceleration – the electric propulsion motor, both provide power to the wheels.  The i-MMD powertrain operates without the use of a conventional transmission.

2.0-liter Inline 4-cylinder Atkinson Cycle Engine
The 2017 Accord Hybrid’s second-generation i-MMD system utilizes a 2.0-liter DOHC i-VTEC 4-cylinder Atkinson Cycle engine that develops a peak 143 horsepower at 6200 rpm and 129 lb.-ft. of torque at 4000 rpm, up from 141 horsepower and 122 lb.-ft. in the previous model. These increases were the result of engine control tuning that together with 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)/Interim Tier3 Bin30 emission standards, while contributing to the Accord Hybrid’s total system output of 212 HP, an 8.2 percent increase from the first-generation i-MMD’s output of 196 horsepower. The Accord Hybrid Sedan has an EPA fuel economy rating of 49/47/48 mpg city/hwy/combined. These EPA fuel economy ratings are based on new, more stringent ratings requirements enacted by the U.S. EPA for the 2017 model year. Based on the new requirements, Honda estimates the 2015 Accord Hybrid ratings would be 48/45/47 (actually rated at 50/45/47 under the previous method), indicating a +1/+2/+1 increase for the 2017 model over the previous version.

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, the engine 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.

The 2.0-liter engine has cylinder bores offset by 6.0 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 enables a high compression ratio of 13.0:1, 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 Dual Bed Catalytic Converter
A key contributor to the Accord Hybrid’s excellent emissions performance is a single dual bed catalytic converter that replaces the previous engine’s two converters. The new converter mounts directly to the front of the cylinder head, close-coupled for fast activation after the engine is started. It uses a thin-wall design that increases internal reaction area and improves efficiency. A high-efficiency exhaust system and the dual bed, high-density catalytic converter help the Accord engine meet stringent LEV3- AT-PZEV(SULEV30)/Interim Tier3 Bin30 standards, which require reduced greenhouse gases compared to lower standards.

Eliminating the second catalytic converter, that was previously mounted downstream on the exhaust system, beneath passenger compartment floor, made room for the exhaust heat recovery device.

Heat Recovery Device
The new heat recovery device contributes to the second-generation i-MMD’s efficiency by helping to reduce power-robbing friction particularly during initial cold weather operation. Located downstream on the exhaust system, the heat recovery device uses hot exhaust gas to warm engine coolant quicker, especially during cold weather conditions. This brings the engine up to normal operating temperature quicker, reducing internal friction and allowing the i-MMD to operate in electric mode earlier. This helps to achieve improved fuel efficiency during cold weather operation.

Electric Motors
The 2017 Accord Hybrid uses two electric motors, a propulsion motor that drives the wheels and a generator motor that produces electricity, both of which have been upgraded from the previous generation i-MMD for more power, smaller size and lighter weight.

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.

Both motors utilize segment conductor winding, where the coil is inserted from the axial direction of the stator core, providing a denser and more compact stator than the previous motors’ distributed winding arrangement, where the coil is inserted from inside the state core. This change enables the electric motors to be significantly smaller and more than 23 percent lighter than the previous motors.

An additional improvement in the motors is the replacement of two larger rotor magnets with three smaller and lighter magnets. The three magnets are arranged in an arc pattern that creates six magnetic poles, which helps to improve torque multiplication.

These changes result in significantly increased output performance. The propulsion motor’s maximum power is raised by 14.8 horsepower to 181 horsepower and torque is increased by 6 lb.-ft. to 232 lb.-ft. The generator motor’s power was raised to 142 horsepower from 140.8 with torque remaining at 62.7 lb.-ft.

Intelligent Power Unit (IPU)
The Accord Hybrid’s intelligent Power unit (IPU), located behind the rear seat, packages a DC-DC converter and a 1.3 kWh Li-Ion battery pack that powers the Accord Hybrid’s electric propulsion motor. Significant changes to the IPU provide the same capacity and output but in a much more compact and lighter package. This was achieved by utilizing VDA standard, high energy density Li-Ion battery cells, unifying the battery ECU and cell voltage sensor into one component and utilizing a single rather than dual cooling duct. These changes reduced the overall volume of the IPU by more than 30 percent to 2.26 cubic feet from 3.32 cubic feet and reduced the weight by almost 13 percent to 99.2 lbs. from 113.8 lbs.

The battery pack is recharged by the propulsion motor operating in regenerative braking mode, and by the generator motor, which is powered by the gasoline engine. Battery temperature is controlled by a fan system that pulls air from the interior of the vehicle via vents located beneath the left rear seat bottom. 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.

Power Control Unit (PCU)
The Power Control Unit (PCU), which is the real brains of the i-MMD system, dictates the power management strategy of the two-motor hybrid system, including motor power and battery recharge. In addition, the PCU increases the electric voltage up to 700 volts, enabling the propulsion motor to realize output as high as 181 horsepower.

As with many components of the second-generation i-MMD, the 2017 Accord Hybrid’s PCU was upgraded. The new design reduced the component weight by 27 percent and reduced its size by almost 23 percent. This, in turn, increased the power density 25 percent by volume. The new floating structure of the PCU’s reactor greatly reduced vibration and high frequency noise.

Along with the greatly reduced size, overall i-MMD component packaging was improved by directly mounting the PCU to the transmission and utilizing a three-phase connector, which eliminated the need for the previous frame mounting bracket and connection cable.

Drive Force Transfer
The Accord Hybrid is not equipped with a conventional mechanical transmission. Instead, motive force transfer is accomplished through the interaction of the Accord Hybrid’s gasoline engine and two electric motors. Coordinated by the IPU, this form of drive force transfer 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 drive force transfer system operates without the need for a torque converter, mechanical pulley or belt. It instead uses two motors for driving and generating power. The system 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, a lock-up clutch 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 operation, 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.

Improving efficiency and reducing weight and size, the drive force transfer system of the second-generation i-MMD integrates the torque limiter within the flywheel.

Automatic Modes
The transmission, with its console-mounted straight-gate shifter, can be operated in two different fully automatic modes. The D (Drive) 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 to assist in more efficient hybrid operation and therefore increased fuel efficiency.

Sport Mode
For the first time the 2017 Accord Hybrid includes a sport mode that provides a more engaging driving experience by adding more battery assist to the propulsion motor for increased acceleration performance. It combines a sportier response to driver input with exhilarating acceleration feel. Sport mode is activated by pressing on the SPORT button located below the transmission straight-gate shifter and can be used in either Drive or Brake mode. A green SPORT icon lights on the instrument panel in this mode.

EV Button
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 operation or Engine Drive operation.

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.)

Accord Hybrid Powertrain Specifications