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HONDA “SMART IMA”
THINK OF Honda’s recently announced hybrid One-Motor Intelligent Dual Clutch Drive as “Smart IMA.” I’ve admired the engineering elegance of the earlier Integrated Motor Assist hybrid except for one aspect: its oddity of cycling the gasoline engine when in pure electric mode.
That is, IMA has an efficient direct linkage of engine/electric motor/gearbox, with a single clutch located between the motor and gearbox. As its name implies, the gasoline engine has the primary role, the electric motor providing assist.
Honda IMA, left; i-DCD, right.
However, again as its name indicates, this electric motor is integrated with the gasoline engine; it resides where you’d expect to find the latter’s flywheel. And this means that any pure EV propulsion still has the gasoline engine churning, albeit producing no power, its pistons being pumped up and down with no combustion.
Years ago, at a press presentation in Japan, Honda engineers were asked about this apparent inefficiency of driving the engine for no good reason. Their answer, a valid engineering response, was that eliminating this cycling would require an additional clutch—and this wasn’t beneficial at IMA’s price point.
Times change. Fuel economy pressures change. And, given Toyota’s current hybrid supremacy, marketing pressures change as well.
Honda i-DCD basics.
Succinctly, Honda’s One-Motor Intelligent Dual Clutch Drive, i-DCD, for short, is IMA with that additional clutch. Said another way, it’s Smart IMA, with the electric motor as primary propulsion and gasoline engine assist.
The 2014 Honda Fit hybrid will have what the company calls Sport Hybrid i-DCD.
The 2014 Fit, the Jazz in other markets, is completely redesigned. To my eye, reflecting current fashion, it’s rather more Nikko than Katsura (see www.wp.me/p2ETap-1hc for an essay on Japanese aesthetics). It’s slated for Japan introduction in September 2013.
The Fit’s gasoline engine is a 1.5-liter Atkinson-cycle inline-four. Details of its electric motor have yet to be released, but it’s known the lithium-ion battery pack will reside aft, atop the rear wheel centerline. The gearbox is a newly designed seven-speed dual-clutch transmission. In fact, don’t confuse this DCT, as Honda calls it, with the DCD.
The DCT is another elegant bit of engineering, one of the earliest being the PDK, Porsche Doppelkupplungsgetriebe. Briefly, DCT promises to provide efficient as well as enthusiastic two-pedal motoring.
Three modes are provided, automatically selected depending on driving environment: EV Drive can be used in startup and light to medium cruising, with the gasoline engine disconnected and shut down. Hybrid Drive has the usual hybrid interaction. Last, Engine Drive offers motoring with no electric contribution (and, hence, no battery drain). The car gains enhanced efficiency of its brake regeneration through automatic engine disconnect during deceleration.
Honda sees i-DCD as part of its Earth Dreams Technology.
All Fit models are expected to offer an option of Honda’s City Brake Active system. A front-end sensor monitors traffic ahead. If a collision appears imminent, driver alerts are provided—and, if ignored, the brakes are automatically invoked. The system also precludes the possibility of pedal misapplication in low-speed maneuvering.
The Fit Sport Hybrid i-DCD has posted 36.4 km/liter (85.6 mpg) on the home-market JC08 test cycle, a bit lower speed and less aggressive than our EPA evaluations. Honda says the added clutch improves previous IMA operation by more than 35 percent. For comparison, a 2013 Civic Hybrid (a larger Honda model) posts 44/44/44 for its EPA City/Highway/Combined; a 35-percent improvement of 44 mpg yields 59.4 mpg. Not bad at all. ds
[Note: Corrections of dates, EV behavior made 6:40 a.m., July 25, 2013.]
© Dennis Simanaitis, SimanaitisSays.com, 2013
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