More powerful, more fuel-efficient direct-injection engines are the main upgrade for the 2008 Porsche Cayenne. The standard Cayenne’s V6 increases from 3.2 to 3.6 liters in displacement, making more torque and about 290 horsepower. Still, acceleration to 60 mph takes eight seconds, which is not respectable enough for a Porsche. The new 4.8-liter V8 in the Cayenne S does better, making about 385 horsepower and getting to 60 mpg in 6.5 seconds. The top-shelf Cayenne Turbo spools up about 500 ponies for a 60-mph acceleration run in about five seconds.