It’s doubtful that fuel prices are the first thing people think about when they buy a sports car, but even automakers primarily concerned with performance need to worry about efficiency. One of the methods Porsche is using is its new coasting function.
It’s found on the new 2012 Porsche 911 Carrera with automatic dual-clutch PDK transmission.
When you’re cruising along in the top seventh gear and you don’t need engine power, the system will temporarily go into neutral to conserve fuel.
“When you come off the gas (without the system) and there’s engine braking, the car slows down because there’s drag,” says Laurance Yap, director of marketing for Porsche Canada. “This removes this effect and allows you to cruise at speed for quite a while, depending on what the conditions are.”
The system is electronic and the gearshift lever doesn’t move into neutral. If the driver puts his foot on the throttle, the engine hooks up again immediately.
“The car slows down a lot less than if you were to take your foot off the gas in a normal condition,” Yap says. Since many drivers are on and off on the throttle on the highway, “it lets you conserve some of this kinetic energy rather than frittering it away with engine braking,” he says.
The engine doesn’t stop running, but since it’s not actively powering the wheels, it drops down to idle speed, reducing its fuel requirement.
The coasting function is one of several fuel-saving features on the redesigned 911 Carrera, along with lighter-weight construction, an auto-stop system that shuts off the gasoline engine when sitting at a light, an electrical system that captures braking energy, and low-rolling-resistance tires. The coasting function can generate fuel savings of 0.2 L/100 km, which isn’t all that much on its own but which combines with other features to bring down fuel consumption. In European testing, the new model achieves 16.3 per cent better fuel economy than the previous 911 Carrera.
The new coasting function is part of the stop-stop function in the PDK transmission, and both can be shut off by the driver if preferred.
And while the driving experience is the top priority for most Porsche owners, Yap says they still think about fuel consumption.
“I think this efficiency is part of the 911 story,” he says.
“The other reality is that whether buyers care or not, we have to do what we can to meet the consumption regulations as well, and all of this is part of that strategy.”
