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Fastlane: Transmissions are important for improving fuel economy too

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By Jeff Lux
FWD Transmissions Global Chief Engineer

With news last week of the four-cylinder 2010 Chevrolet Equinox achieving 32 mpg highway in EPA testing - best-in-class for a compact crossover vehicle and 2 mpg better than we expected - I started to reflect a little on all the powertrain systems and technologies that must work together to reach such an impressive number, especially when you consider the Equinox seats 5-passengers comfortably and weighs close to 4,000 lbs. Being a transmissions engineer, I naturally gravitated to the vehicle’s six-speed automatic transmission.

When people talk about fuel economy, they generally focus more on the fuel savings from the engine than anything else. And true, technologies like active fuel management, turbocharging or in the case of the Chevy Equinox, direct injection help to greatly improve a vehicle’s fuel economy.

But what about the part of the powertrain that gets the power to the road - the transmission? Improving fuel efficiency is key to GM’s current and future product plans, and from a transmission standpoint, we are working on a number of technology options to achieve that goal.

One of the most recent advances for our transmission portfolio is the large scale availability of six-speed automatic transmissions across a wide range of GM cars and trucks. Six-speed automatics are available in GM vehicles from small cars to SUVs and pick-up trucks.

In six short years, we’ve developed and launched nine new six-speed automatics for more than 40 rear-wheel, front-wheel and all-wheel drive vehicles. And by the end of the year, we will launch another six-speed variant for a total of 10 new six-speed automatics!

Six-speeds provide the best of both worlds, delivering both improved fuel economy and performance. On average, a six-speed transmission will provide up to four percent improved fuel economy compared to a four-speed automatic transmission. In addition, a six-speed provides up to a seven percent improvement in 0-60 performance. And the six-speed’s benefits don’t stop there. Because six-speeds have a wider range of gear ratios to choose from, the engine speed can be optimized for the driving condition. The result is lower engine speeds for many conditions and better overall vehicle noise quality.

We are pursuing many more transmission advancements that have the potential to save even more fuel, such as new transmission fluids, reducing internal friction, and one of the most promising, software that controls the lock up of the torque converter in the transmission.

One of the great features being introduced for 2010 in the four-cylinder/six-speed transmission combinations of the Equinox and GMC Terrain is ECO mode. ECO mode is a vehicle fuel saving feature that the driver can activate by pressing a button on the console. The transmission plays a central role in ECO mode as it increases fuel economy by operating the engine at its optimum efficiency points. This is partially accomplished by upshifting earlier, locking the torque converter at lower RPMs and holding higher gears for longer periods of time than in normal mode operation. Driving in ECO mode can improve your fuel economy by up to three percent or 1 mpg and for customers more attuned to their vehicle, may slightly change the vehicle’s drive and feel to maximize fuel efficiency.

While hybrids and electric vehicles are getting a lot of coverage nowadays, we’re also working on a broad range of internal combustion and automatic transmission technology solutions to provide better fuel economy for customers now and in the future. I can’t give away too many more details on our future plans, but stay tuned.

I look forward to reading your thoughts and comments.

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GM's switch to using 6ATs over 4ATs has been very impressive. I hope they do the same for their hybrids.

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GM's switch to using 6ATs over 4ATs has been very impressive. I hope they do the same for their hybrids.

it's taking them long enough to switch isn't it...

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