Wednesday, October 30, 2019

Honda's Unconventional Hybrid System Has a One-Speed Gearbox (w/ Video)


Gasoline-electric hybrids are typically known for one thing: environmentally-conscious motoring. With that, expect sky-high fuel mileage and low tailpipe emissions at the expense of a sordid driving experience. Luckily for enthusiasts, Honda realized that the typical hybrid solution also didn’t fit well with their sporty nature. And so, they’ve developed this: the Sports Hybrid Intelligent Multi-Mode Drive or Sports Hybrid i-MMD.

While the name itself is clunky, the technology behind it is amazing. It automatically switches between three driving modes to provide the highest possible efficiency when driving. These modes comprise: EV Drive, where the lithium-ion battery supplies power to the electric propulsion motor directly; Hybrid Drive, where the engine supplies power to an electric generator motor, which in turn supplies it to the electric propulsion motor; and Engine Drive, where the engine is connected directly to the wheels via a lock-up clutch.



In most urban or city driving situations, the i-MMD will shuffle between Hybrid Drive and EV Drive. In Hybrid Drive, excess power from the petrol engine can also be diverted to recharge the battery via the generator motor. EV Drive permits pure-electric propulsion and can give a zero emissions range of about two kilometers depending on the driving condition and battery charge.

Meanwhile, the Engine Drive mode is the most efficient set-up for cruising at higher speeds and it can be supplemented by an on-demand power ‘boost’ from the electric propulsion motor to supplement engine torque under certain conditions. At a 60 km/h cruise, the i-MMD will typically run in EV Drive for more than half the time. At 100 km/h, it will be in EV Drive for approximately one third of the time.

The software ‘brain’ of the i-MMD system decides when to shuffle between these modes to maximize efficiency, without disturbing the driver or requiring any further thought or input from them.

Now, while the set-up resembles other hybrid vehicles—where an Atkinson cycle gasoline engine, propulsion motor, generator motor, and power control unit are all located under the hood, and a lithium-ion battery back housed under the trunk, the i-MMD does have one innovation: a fixed gear transmission.



Rather than using a conventional transmission, a single fixed-gear ratio creates a direct connection between moving components, resulting in a smoother transfer of torque. This format means Honda’s system is more compact than a planetary eCVT typically found in other hybrid vehicles, as well as being more refined.

Moreover, the transfer between power sources, including the engine stop-start function, is virtually imperceptible. The smooth transfer of torque means there is no driveline shunt or undesirable feedback through the pedals or steering wheel, and the near-silent powertrain means a vehicle equipped with i-MMD boasts outstanding NVH.

The first application of the i-MMD system happens to be larger Honda vehicles, particularly the likes of the CR-V and the Accord. In this set-up, the 2.0-liter i-MMD makes a respectable 184 horsepower and 315 Nm of torque—figures that match their conventionally-powered counterparts featuring the 1.5-liter VTEC Turbo engine. But, based on WLTP test protocols, it does 18.87 km/L. However, the more interesting application of the i-MMD system is found in the Civic-based Honda Insight. With a smaller, 1.5-liter displacement, it still makes a healthy 151 horsepower and 267 Nm of torque—yet, it delivers 22.1 km/L. Though Honda hasn’t confirmed it just yet, if this is the very same engine that they’ll fit in the all-new Jazz Hybrid, then you’re looking at a formidable pocket rocket.

As part of their 2030 Vision, the Honda Sports Hybrid i-MMD will form the cornerstone of their plan to reduce their emissions. Yet, it’s equally clear that while they want to produce environmentally-sound vehicles, they still aren’t willing to give up their sporty nature yet. By coming up with unique methods to electrify their vehicles such as the i-MMD system, Honda is able to chart a unique path, driven by one thing: their challenging spirit.

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