Today’s active cruise-control systems can read the road, spot impending collisions, and automatically apply the car’s brakes. A few even steer to some degree. Seemingly every new luxury car boasts an incremental upgrade—now with gopher detection!—but by decade’s end, Porsche will debut an active cruise with one feature that no one else has mentioned: excitement. Its InnoDrive system will allow for cornering at up to 0.70 g. That’s more sustained lateral acceleration than most casual drivers have ever experienced and the kind of g-force that has even seasoned lappers reaching for the oh-crap handles.
-Currently under development by Porsche on winding two-lane roads outside Weissach, Germany, InnoDrive enlists all the usual suspects of semi-autonomous driving plus two extra pieces of data: the grade of the pavement and the radius of the turn, both of which are stored in the navigation system’s database. This helps the car paint a thrsee-dimensional picture of the road, allowing the onboard computers to set the speed for ultraefficient cruising and perfect 0.50-g turns (the approximate lateral limit in the middle of the three driver-selectable modes; the most efficient setting corners at 0.70 g). All the driver needs to do is steer.
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InnoDrive’s aim is to deliver the driver to a destination as quickly as possible while consuming the least amount of fuel. Those goals are not mutually exclusive, Porsche says, claiming that InnoDrive can diminish real-world fuel consumption by 10 percent while shortening drive time by 2 percent. The keys are minimizing deceleration for cornering—hence the high g-loading—and accelerating quickly, sometimes even at wide-open throttle, over short periods of time in the most frugal part of the engine’s operating range [see below]. Incremental fuel-economy gains come from speeding up ever so slightly just before an incline—rather than reacting to the grade after the car has slowed a bit—and braking or coasting when entering cities to perfectly match the car to the speed limit. InnoDrive operates with the precision of a dual-clutch downshift, except that doing its job takes longer than a quarter of a second.
-We sampled an early InnoDrive prototype over a 14-mile loop and can say that it is the most entertaining cruise control ever conceived. Pulling your feet off the pedals is a totally alien experience on a winding two-lane, but it’s something the La-Z-Boy jockey in us could get used to. Plus, we welcome any sign that the encroaching automation of automobiles won’t be totally boring.
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Please Be Specific
-Nothing is more important to efficiency-minded engineers than an engine’s brake-specific fuel consumption (BSFC), except possibly Star Wars. Unlike mpg, which indicates the distance traveled on a gallon, BSFC is the measure of how efficiently an engine makes its power. The lowest BSFC is the point at which the engine is making the most power from every gram of fuel, which is rarely at the engine’s power peak. BSFC is always best at wide-open throttle near max torque. Engineers hunt for efficiency via maps like this, which plot torque versus engine speed versus fuel consumption. The rings are different for nearly every engine.
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from Car and Driver Blog http://ift.tt/1DPeu7h
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