Honda’s Excellent Two-Mode Hybrid System Wins GCJ Technology Award

Discussion in 'In the News' started by xcel, Jan 24, 2014.

  1. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    [​IMG] Finally an award recognizing Honda’s outstanding contribution to low emissions and excellent midsize vehicle efficiency.

    [​IMG]Wayne Gerdes - CleanMPG - Jan. 24, 2014

    The i-MMD (Intelligent Multi-Mode Drive) Sport Hybrid system achieves the best efficiency in the world by combining a newly-developed direct injected and atkinsonized 2.0L engine, an 100% electric CVT built around two built-in motors acting in series with a lock-up clutch, and a Li-Ion battery, and also by optimally switching between three drive modes according to the driving situation.

    For the ninth-generation 2014 Accord Hybrid Electric Vehicle (HEV) and Plug-In Hybrid Electric Vehicle (PHEV), Honda designed and built an entirely new 2 motor hybrid 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 EV drive, hybrid drive and engine drive.

    The Accord Hybrid has EPA fuel economy ratings of 50/45/47 mpg city/highway/combined that gives it the best-in-class rating for four door sedans.

    2.0L I4 Hybrid Features
    • 2.0L DOHC, i-VTEC I4
    • 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
    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 I4 and the electric motor to suit the driving conditions moment to moment.

    EV - 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 - 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 - 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..

    The Atkinsonized 2.0L I4 by itself develops 141 horsepower and 122 lb-ft. of torque. It is one of the world’s most thermally efficient powerplants available anywhere in the world. 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 Accord Hybrid’s total system output (peak horsepower of both the gas engine and the two-motor hybrid-drive system) is 196 hp allowing the midsize to do the 60 mph dance in under 8 seconds.

    i-MMD cutaway from the floor of the 2014 NAIAS


    Engine Internals

    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 2.0L 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.

    The Accord Hybrid I4 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.

    The Accord Hybrid's 2.0L 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.


    The Accord engine provides excellent emissions performance thanks to 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.

    Motors - The Accord 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. 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.

    Li-Ion - The Accord Hybrid's integrated Power unit (IPU), located behind the rear seat, is 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 - 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.

    The Award

    Honda's Earth Dreams Technology two-motor hybrid system that helped the 2014 Accord Hybrid earn an EPA-rated fuel economy of 50/45/47 mpgUS city/highway/combined has been named to Green Car Journal's Top 10 Green Car Technology List for 2014. Part of an expanding lineup of Honda Earth Dreams Technology powertrains, the innovative two-motor hybrid system generates class-leading fuel efficiency without compromising performance.

    The Two-Motor Hybrid System, available on the EPA-rated 50 mpg Accord Hybrid and the EPA-rated 115 MPGe Accord Plug-in Hybrid, almost seamlessly blends electric-only, hybrid and engine drive modes along with powerful regenerative braking to provide responsive and efficient performance in a wide range of driving situations. As the powertrain shifts seamlessly among the three driving modes, the system utilizes power from the i-VTEC® 4-cylinder engine and the electric motor to suit the driving conditions moment to moment.

    The Green Car Technology awards honor important enabling technology helping to create a new generation of fuel-efficient, alternative-fuel, or low-emission vehicles. Technologies considered for the award range from advanced powerplants and drivetrain components to on-board systems that work toward increasing efficiencies, reducing petroleum use or improving environmental impact. Qualifying technologies must be in use by vehicle models currently on the market today.

    And of course our drive(s) of both the PHEV and HEV proved Honda’s prowess at building the current best Hybrid drivetrain in the world.

    2014 Honda Accord HEV First Drive Result


    During our 2014 Honda Accord HEV Review, from a Shell on Torrance Blvd. and the I-110 in Torrance, CA to Marian’s home in San Diego showed the Accord HEV covered 97.5 miles at 81.4 mpg actual vs. 96.4 miles at 80.1 mpg displayed.
  2. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    We've certainly come a long way. When I bought my first new car , the average sedan had a 6 liter V-8. And maybe got a real-world 17 MPG highway. My 73 Pinto station wagon was 2 liters , but highway fuel economy was only 27 MPG at 55 MPH ( but it was December).

    Thanks for all this additional detail on this excellent car, Wayne.
  3. rhwinger

    rhwinger Well-Known Member

    Thanks Wayne, very interesting read, especially the eCVT. This really sounds a major change for the better.

    Any idea how battery SOC is monitored and maintained? I've read a little on previous Honda battery charge systems, in that they seem to compute SOC by tracking current draw and charge, instead of more directly monitoring battery voltage conditions. Which I believe may be responsible for problems.


  4. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Bob:

    All battery SoC algorithms are Guesstimates and they use charge, current, voltage, temperature, and cell bank voltage, plus some other stuff I do not know about. IMA was controlled well enough but it was too small a pack allowing too much in and outflow and at times, dug too far into its usable range apparently.

    Either way there is a risk with all batteries on this but the manufacturers Li-Ion suppliers have a really good handle on it today.

  5. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    My take: the way IMA determines battery status didn't cause problems, but with deteriorating batteries the recal was a symptom of deteriorating battery. The software sees a disparity between anticipated and actual, so goes into recalibration.

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