2018 Honda Accord Hybrid Drivetrain Details

Discussion in 'In the News' started by xcel, Oct 13, 2017.

  1. xcel

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

    [​IMG] More efficient… How much more remains to be seen?

    Wayne Gerdes – CleanMPG – Oct. 13, 2017

    2018 Honda Accord Hybrid – Pricing and EPA (hopefully > 49/47 mpg city/highway of the current Accord Hybrid) to be announced very soon.

    2018 Honda Accord Hybrid


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    2018 Honda Accord Hybrid Powertrain Overview
    • Atkinsonized 2.0L I4
    • Engine maximum output: 143 hp and 129 lb.-ft. torque
    • Multi-port fuel injection (MPFI)
    • 13.5:1 compression ratio
    • Drive-by-Wire
    • Maintenance Minder system optimizes service intervals
    • 100,000-mile engine tune-up interval
    • Regular Unleaded fuel recommended
    • Electric motor output: 181 peak hp
    • Total system power: 212 hp
    • 8 yr/100,000-mile or 10 yr/150,000-mile Li-Ion battery limited warranty
    The 2018 Accord Hybrid's third-generation i-MMD Two-motor hybrid system is a highly efficient powertrain utilizing an Atkinsononized 2.0L I4 with 40 percent thermal efficiency, up from 38.9-percent in the previous 2017 Accord Hybrid, and the highest thermal efficiency of any mass-produced Honda engine.

    The engine is paired with two electric motors, the first drive motors in the world to use magnets containing no heavy rare-earth metals via a new Honda-patented design that reduces both cost and weight.

    Like the 2017, the 2018 Accord Hybrid has 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).

    2018 Honda Accord Hybrid

    Under the hood.​

    EV - All-electric drive 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 - The electric propulsion motor 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 in a serial Hybrid operation. 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.

    Engine - When cruising at higher speeds, the gasoline engine provides propulsion via a high 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 mode, 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.

    From the 2017, this is the area of operation in which NVH rose significantly, drivability became somewhat abnormal with a heavy CVT rubber band effect, and efficiency declined rapidly. Hopefully the new motors and programming has reduced the CVT rubber band action, NVH, and higher speed efficiency hit significantly.

    Key contributors to the improved thermal efficiency of the 2.0L I4 is a change in exhaust gas recirculation tuning and reductions in operating friction.

    2018 Honda Accord Hybrid Drivetrain

    New non-rare earth magnet designed two motor cutaway.​

    The engine uses cast-in iron cylinder liners while 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 includes an internal balancer 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 I4 engines.

    The cylinder bores offset by 6.0 mm to help reduce piston-sliding friction by providing the connecting rods less of an angle off center during the 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 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.

    The engine has a 34-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 13.5:1, yet the engine still operates on regular unleaded fuel.

    An advanced valve-control 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.

    2018 Honda Accord Hybrid Wheel

    Not drivetrain related per say but they are decent looking wheels.​

    A key contributor to the Accord Hybrid's excellent emission performance is a single dual-bed catalytic converter. The 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.

    A heat recovery device contributes to the third-generation i-MMD's efficiency by helping to reduce friction during cold-weather startup and initial operation, prior to normal engine temperatures being reached. 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.

    The 2018 Accord Hybrid uses two new-generation electric motors, both of which have been upgraded from the previous generation i-MMD. The Honda-developed electric motors that are the first permanent magnet drive motors in the world to use magnets containing no heavy rare-earth metals. The propulsion motor is rated at 181 hp and 232 lb.-ft. of torque.

    When in regenerative mode, the propulsion motor converts the kinetic energy of the decelerating 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.

    The Accord Hybrid's completely reworked intelligent Power unit (IPU) is now 32-percent more compact and has been repositioned under the rear seat base, instead of in the trunk, behind the rear seatback as in the previous generation Accord Hybrid. This repositioning means that the Accord Hybrid offers the same roomy trunk utility and 60/40 split-folding rear seatback versatility of the non-hybrid Accord models. The IPU packages a reconfigured Li-Ion battery pack that powers the Accord Hybrid's electric propulsion motor. Improved battery control systems and revised battery chemistry allow the new battery to operate over a broader state-of-charge range for improved efficiency.

    2018 vs 2017 Honda Accord Hybrid Drivetrain Specifications Comparison

    Not much change for the third gen Hybrid Drivetrain.​

    The battery pack is recharged by the propulsion motor operating during regenerative braking, 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 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.

    The Power Control Unit (PCU), which dictates the power management strategy of the two-motor hybrid system, including motor power and battery recharge, now includes the DC/DC converter and is mounted in the engine compartment.

    Just like the previous model, the Accord Hybrid is driven 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 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.

    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.

    In the Accord Hybrid, new steering wheel-mounted selector paddles allow the driver to select between four levels of regenerative braking performance. The right paddle adds regenerative braking and the left paddle reduces regenerative braking.

    The Accord's Hybrid drivetrain requires no scheduled maintenance for 100,000+/- miles or more, other than periodic inspections and normal fluid and filter replacements. The first tune-up includes water pump inspection, valve adjustment, and the installation of new spark plugs.

    2018 Honda Accord Hybrid


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  2. ALS

    ALS Super Moderator Staff Member

    Hi Wayne,

    Well that isn't going to make the Chinese happy.:p

    Remember a few years ago when the Chinese were putting limits on the amount of rare earth materials used to make high strength magnets just to be difficult and raise the prices on those materials for western companies?

    Hope they're happy, all they did was kill off a large piece of the market for those rare earth materials.

    BillLin likes this.
  3. Jay

    Jay Well-Known Member

    The press played the neodymium thing with China up to "just being difficult" but the truth is that neodymium is no less abundant in the earth's crust in the US than in China. Nd is rare. That means you have to process a lot of rock to obtain just a little of it. That means you have to cause a lot of environmental damage to get meaningful quantities of the stuff. The Chinese are more willing to trash their environment for industry than we are. That's why they have it and we don't. If they want to use the Nd they obtain at great cost for their own use that's their right.

    Incidentally, Nd is a byproduct of nuclear fission. We could harvest Nd (and many other valuable, rare, elements) from spent nuclear fuel rods but a ban on processing nuclear fuel from the Carter years means we have to throw those valuable rods away. This wastes many recyclable byproducts, some of which are tens of thousands of dollars a gram, and it causes a nuclear waste "problem". The French choose not to sabotage their nuclear energy program and have become world experts at harvesting all those valuable nuclear byproducts and recycling the fuel. Maybe we should follow their lead.
  4. alster

    alster Well-Known Member

    I don't think the 2018 Honda Acccord Hybrid will meet or beat the 2018 Toyota Camry LE hybrid when it comes to EPA Fuel Economy rating. Its hard to beat 52 mpg average for a full size passenger car that weighs 3,500 lbs.

    I have a feeling the reason that we don't know what the EPA will be for the Accord Hybrid is because they can't beat the Camry Hybrid otherwise we would have
    already known the EPA rating. Just a hunch.....
    TheFordFamily, BillLin and xcel like this.
  5. thunderstruck

    thunderstruck Super Moderator

    Need to see what Wayne manages to wring out of it. I'm ready for the next step in cars, looking for basics like heated mirrors. It's so ghetto to have to wipe the mirrors every morning with a paper towel because heated mirrors aren't an option on my Prius 3.
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  6. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Heated mirrors are standard on my 2015 Prius , base model ( Two? ). Somehow , I managed to survive driving for 45 years without them.
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  7. Jay

    Jay Well-Known Member

    I've mentioned this before, but I test drove the hybrid Accord, hybrid Sonata, and hybrid Camry a couple of years ago. The Accord was my favorite of the three by quite a margin. It was the best looking, best handling, and had the best driving dynamics. The day I drove it, it was blowing 30mph steady with gusts up to 50mph and the Accord drove like it was in still air. It was pretty amazing. On the bad side was the front seat that wouldn't go back far enough for me. A great big full size car with piddling leg room in the front! Completely inexcusable. And then the price. It was just stupid expensive compared to the other two. The Sonata was the roomiest. No lack of room in the front or back. It had the poorest driving dynamics of the three but the lowest cost. The Camry had the best instrumentation.
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  8. Carcus

    Carcus Well-Known Member

    I've got 1.5 liters of forced induction aluminum fury catapulting me down the super-slab, ... glancing into the vapor trail encapsulated past is but a dangerous distraction.
    I keep 100% of my steely focus on the road ahead.
  9. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Someone has a thesaurus and dictionary ! I like it. Don't forget "with the fury of 174 Japanese horses" .
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  10. Carcus

    Carcus Well-Known Member

    In my head! lol

    Shake out some 91 octane oats and another 15 or 20 come into the stable.
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  11. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    What would that entail? Valve clearance adjustment, spark plug replacement, replacement of a rubber timing belt?
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  12. BillLin

    BillLin PV solar, geothermal HVAC, hybrids and electrics

    Good guess.

    I guess it must use a timing chain?
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  13. Trollbait

    Trollbait Well-Known Member

    Or an oil soaked belt like in the Ford hybrids, which is more akin to the metal belt in a CVT.
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  14. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Yeah maybe, because belts they're pretty strident about changing them on-time, and that was around 100K km's if I recall correctly, with our '80's~'90's Accords.
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  15. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I had no problem with my Hondas with timing belts. Except maybe the expense , if you don't do the labor yourself.

    However , don't most cars come with timing chains today ? Is anyone aware of cars ( in the civilised world) still being sold with belts ?
    Mendel Leisk, xcel and BillLin like this.
  16. Trollbait

    Trollbait Well-Known Member

    I know the base 1.8L in the Sonic had a belt. So did the V6 in the 2006 CrossTour and 2005 Camry. Did VW ever stop using them in their diesel?

    Timing belts have a slight advantage in noise and efficiency over a chain, so I expect they'll stick around.
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  17. Jay

    Jay Well-Known Member

    I don't think Honda uses a timing belt in any automotive engine made this century. The biggest advantage of a timing belt is that they don't stretch as chains do. A timing chain lengthens as the pin/bushing interface wears which causes valve timing to slip which hurts performance and fuel economy. A belt retains valve timing but they break suddenly which destroys the valves and sometimes the whole engine if it has interference valves. A chain is more robust and resists breaking much better. Most modern automotive engines have variable valve timing on either the intake or exhaust valves or both. This allows designers to go back to the more robust chains because the valve phasing floats in the VVT mechanism. Precise valve timing is maintained by the VVT even as the chain stretches.
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  18. BillLin

    BillLin PV solar, geothermal HVAC, hybrids and electrics

    The timing chain/belt's just conveying relative positioning of the cylinders to other parts of the engine isn't it? I had been wondering if there wasn't some other way for the VVT and ignition to function without the timing chain/belt. You would think with all that computer control, etc... I'm not mechanically inclined so perhaps these are stupid thoughts. Thanks.
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  19. Mendel Leisk

    Mendel Leisk 2010 Prius (CAN Touring) Staff Member

    Eliminate the camshaft, go back to push rods, per Harley? Nonono.
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  20. xcel

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

    Hi All:

    While at the Texas Auto Writers Association (TAWA) Truck Rodeo in Austin, TX for the past 5-days, I spoke with one of the journalists from TFLCar/Truck that drove the 18 Accord Hybrid Prototype at the Accord short lead last month. He was not well versed in hybrid terminology but his initial impressions was he liked it. Drilling down into the CVT action and high NVH at speed from the current to next gen 2018, he said, "Come to think about it, yes there was a lot of CVT rubber band effect and engine noise when accelerating hard and at higher speeds was higher than the non-hybrids."

    Besides the efficiency fall off at highway speeds, this high load NVH issue still appears to be an Achilles heel of Honda's two-motor CVT. 18 Accord Hybrid EPA ratings and pricing should be out very soon...

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