Could your next car get 86 mpg? It might if it’s a Honda. The next-generation Honda Fit subcompact will be unveiled this fall and arrive in the US in the first half of 2014. Most of the buzz over the new Fit, called the Honda Jazz in some countries) is the hybrid version, which promises a 35% improvement in fuel economy. The US currently gets the gasoline Honda Fit and EV Fit — not the hybrid Fit — but that could change with the next model.
On a Japanese test cycle, 2014 Fit Hybrid fuel economy will be on the order of 2.7 liters consumed per 100 km or 85.6 US mpg. That’s a mathematical conversion that doesn’t account for the US test cycle. But still, it could be the most efficient hybrid if and when it arrives stateside. Currently the most efficient non-EV cars sold in the US are the Toyota Prius C and Toyota Prius, each with 50 mpg combined EPA rating, 53 mpg and 51 mpg city ratings for the Prius C and Prius, respectively. The 2013 Honda Fit gets 29-31 mpg combined depending on the transmission or 33-35 mpg highway; the Honda Fit EV gets 118 mpg-e (miles per gallon equivalent), best in the category the EPA calls small station wagons.
Atkinson engine, 7-speed double clutch transmission, electric motor
Under the umbrella of Honda’s Earth Dreams Technology program, the new Fit Hybrid will be the first to employ Honda’s Intelligent Dual Clutch Drive system, or i-DCD. The gasoline power comes from a 1.5-liter, four-cylinder Atkinson cycle engine. A single electric motor is packaged with a seven-speed dual clutch transmission, linked through an intelligent power unit (IPU) to a lithium-ion storage battery. An Atkinson engine has an effectively shorter compression stroke (when the piston moves upward) than the downward power stroke, accomplished by not immediately closing each cylinder’s intake valve. It captures more of the power in the fuel-air mixture.
When starting out, the clutches disengage the gas engine and the Fit Hybrid starts off on battery power. The clutches engage the engine and gearbox under sporty (hard) acceleration and at higher speeds. When the Fit Hybrid decelerates, the gas engine is again disengaged.
Honda has claimed a 35% increase is compared to the current Fit Hybrid’s integrated motor assist (IMA) configuration. The IMA electric motor only runs when the gasoline engine runs, functioning much like a turbocharger. This is called a mild hybrid or weak hybrid configuration. A hybrid such as the Prius that can run on battery power alone is a strong hybrid, and who wouldn’t prefer strong over mild, let alone weak?
IMA may be cost-effective tech, but lots of hybrid owners want to see — and show their friends — a car that runs on battery alone for a mile or two. This is what happens when you let engineers have input into how a company runs: They pick solutions that make cost-effective sense. Sometimes the market agrees, other times not. Honda has long argued nobody needs an engine of more than six cylinders and it turns out they’re right, but that hurt the Acura brand competing against V8 offerings from Lexus, Audi, BMW and Mercedes-Benz the last two decades. Honda has also been one or two gears shy of the competition in transmissions, arguing that four or five forward gears was fine — “look at our mpg figures, not the numbers of gears.” Now, they too are creeping upwards to as many as seven (the industry record is currently nine). The IMA hybrid is giving way to the i-DCD hybrid. At the very least, IMA served its purpose and Honda is moving on to a more efficient technology.
Next page: Flavors of Honda hybrids
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