Honda 3L SOHC V-6/IMA Hybrid

Back in the day, hybrid-electric vehicles were quirky research projects that seemed to have some powertrain engineers unduly distracted. The first prototype HEV drivelines were whiny, sniveling, evil things, bucking and wheezing and constantly laboring.

Honda Motor Co. Ltd. smacks down that image forever with the all-new Accord Hybrid. Its 3L SOHC V-6 already was a 10 Best Engines winner on its own last year, and now Honda’s engineers have improved it – yeah, we said “improved” – by adding the company’s sophisticated Integrated Motor Assist (IMA) hybrid system.

And there’s more: Honda’s technical boffins also cobbled in the company’s new cylinder-deactivation system, Variable Cylinder Management (VCM). Honda says this phalanx of technologies in the Accord Hybrid means fuel-economy nirvana without the gritty aftertaste. Performance without penalty, if you will.

The basic IMA philosophy already has been shown with Honda’s two other HEVs, the Insight, which started it all, and the Civic Hybrid. The setup has come to be known as a “mild” hybrid: An electric motor acts on the engine crankshaft to “assist” the gasoline engine when extra boost is needed.

Accord Hybrid powertrain delivers serious efficiency gains.

The electric motor itself cannot propel the vehicle, but it does reverse its operation when the vehicle is decelerating, becoming a generator that returns normally wasted deceleration energy to a battery pack. That electricity later is used when the electric motor is in “assist” mode.

In the Insight and Civic Hybrid, IMA works as billed. Economy is markedly enhanced – excitement is not. Even with IMA’s boost, their tiny, downsized engines usually are strained to achieve pace-parity with surrounding traffic.

The Accord Hybrid, though, ushers in the new era of what we call “performance” HEVs. The Accord Hybrid’s 3L SOHC V-6 is not downsized or detuned. In fact, IMA adds a respectable 15 hp to the 3L’s already stout 240-hp standard rating. The third-generation IMA, enhanced in many ways, also provides a torque injection of as much as 100 lb.-ft. (136 Nm).

Now throw in VCM, which cuts the operating cylinder count to three during light-load operation, and there’s some serious efficiency in the offing. The Environmental Protection Agency (EPA) rating says the Accord Hybrid gives up 29 mpg (8.1 L/100 km) in the city and 37 mpg (6.4 L/100 km) on the highway; those numbers respectively represent gains of 38% and 23% over the same car with the 3L V-6.

Honda believes so strongly in IMA and VCM that it says those figures will be much more representative of real-world fuel economy than has been the early experience with some HEVs.

The Accord Hybrid’s performance is sparkling, and nobody will leave the car saying HEVs still are weenie mobiles. This remarkable interplay of technologies works seamlessly, usually when decelerating, when a lot of electrons are trading places. But the hybrid powertrain’s ministrations never are more than remotely distracting.

The Accord Hybrid’s integration of IMA and VCM with Honda’s impressive 3L SOHC V-6 is a triumph of engineering and speaks volumes about the depth of Honda’s powertrain engineering ability. That engineering makes the Accord Hybrid the first HEV that stands up to conventional powertrains with no excuses.

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