Gentlemen, Stop Your Engines
Clever engineering makes Porsche’s hybrid genuinely efficient
Few vehicles flaunt their gas-chugging power as proudly as a Porsche Cayenne, so it’s natural to be suspicious of the hybrid version. Can this racecar-like SUV really improve gas mileage and still be a Porsche?
Thanks to several technological tweaks, yes. First, a more-efficient supercharged 3.0-liter V6 replaces the V8. The gas engine is paired with a 47-horsepower electric motor, and the two are linked with a decoupling clutch, so either one can run the vehicle independently. The motor is capable of handling the load alone at up to 37 mph. Together the pair flings the SUV from 0 to 60 mph in 6.1 seconds. Yet the hybrid gets an estimated 20 mpg city and 25 mpg highway, a 25 and 14 percent gain over the non-hybrid version. It also does tricks: At up to 97 mph, when you take your foot off the accelerator, the engine disengages from the drivetrain and shuts down. Here’s how this “sailing” mode lets you briefly zoom without any power at all.
How to Drive Gas-Free at High Speeds
Lift Off the Gas Pedal…
when coasting at high speeds, and the gas engine powers down. A decoupling clutch disconnects the gasoline engine from the electric motor and the rest of the drivetrain, freeing the drivetrain from the drag that the powered-down engine places on it and allowing you to coast farther, fuel-free.
powered by unhindered momentum. In this mode, which Porsche calls “sailing,” the electric motor runs in reverse, acting as a generator that harvests kinetic energy to recharge the hybrid system’s nickel-metal-hydride rear battery.
to speed up again. A computer coordinates the transition back to gas power. The decoupling clutch reconnects the gas engine to the drivetrain within 300 milliseconds, and the electric motor provides an additional boost for highway acceleration without a perceptible lag.