As of October, the most fuel efficient mid-sized sedan in America is the Honda Accord. Or so Honda says. After all, Ford has been trumpeting a matching 47 MPG combined from their Fusion. Who is right? And more importantly, can the Accord get Honda back into the hybrid game after having lost the first initial hybrid battles with their maligned Integrated Motor Assist system? Honda invited us to sample the 2014 Accord Hybrid as well as a smorgasbord of competitive products to find out.
I have always been a fan of “elegant and restrained” styling which explains my love for the first generation Lexus LS. That describes the 2014 Accord to a tee. Like the regular Accord, the hybrid is devoid of sharp creases, dramatic swooshes, edgy grilles or anything controversial. This is a slightly different take than the Accord Plug-in which swaps the standard Accord bumper for a bumper with a slightly awkward gaping maw. In fact, the only thing to indicate that something green this way someday are some grille inserts and LED headlamps on the top-level Touring model.
Being the drivetrain geek that I am, what’s under the hood of the Accord hybrid is more exciting than the Corvette Stingray. Seriously. Why? Because this car doesn’t have a transmission in the traditional sense. Say what? Let’s start at the beginning.
Things start out with the same 2.0L four-cylinder engine used in the Accord plug-in. The small engine is 10% more efficient than Honda’s “normal” 2.0L engine thanks to a modified Atkinson cycle, an electric water pump, cooled exhaust gas return system, and electric valve timing with a variable cam profile. The engine produces 141 horsepower on its own at 6,200 RPM and, thanks to the fancy valvetrain, 122 lb-ft from 3,500-6,000 RPM.
The engine is connected directly to a motor/generator that is capable of generating approximately 141 horsepower. (Honda won’t release specific details on certain drivetrain internals so that’s an educated guess.) Next we have a 166 horsepower, 226 lb-ft motor that is connected to the front wheels via a fixed gear ratio. Under 44 miles per hour, this is all you need to know about the system. The 166 horsepower motor powers the car alone, drawing power from either a 1.3 kWh lithium-ion battery pack, or the first motor/generator. Over 44 miles per hour, the system chooses one of two mods depending on what is most efficient at the time. The system can engage a clutch pack to directly connect the two motor/generator units together allowing engine power to flow directly to the wheels via that fixed gear ratio.
Pay careful attention to that. I said fixed gear ratio. When the Accord Hybrid engages the clutch to allow the engine to power the wheels directly (mechanically), power is flowing via a single fixed ratio gear set. The fixed gear improves efficiency at highway speeds, reduces weight vs a multi-speed unit and is the reason the system must operate in serial hybrid mode below 44 mph. There is another side effect at play here as well: below 44 MPH, the system’s maximum power output is 166 horsepower. The 196 combined ponies don’t start prancing until that clutch engages.
So why does Honda call it an eCVT? Because that fits on a sales sheet bullet point and the full explanation doesn’t. Also, a serial hybrid can be thought of as a CVT because there is an infinite and non-linear relationship between the engine input and the motor output in the transaxle.
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