Lighter yet roomier, quicker but more fuel-efficient, now genuinely luxurious inside and more obviously a Porsche outside. There's a lot to like about the second-generation Cayenne. But not the gasoline-burning engine under the hood of the $46,700 base model, which goes on sale this fall.

This 3.6-liter V-6 is an updated version of the engine introduced at the 2007 midlife makeover of the first-generation Cayenne. It's a member of the Volkswagen Group's long-lived, narrow-angle, vee-engine family. Designed in the late 1980s, it first appeared in Europe (in the VW Passat) in 1991, and has been persistently developed over two decades, including, in the middle of this decade, the adoption of a 10.6-degree angle instead of the earlier 15 degrees between cylinder banks.

On paper, the engine in the least expensive version of the new Cayenne looks fine. Check the maximum outputs and you'll see the number 295 both times. But while the power and torque figures are highly competitive, driving it reveals that the engine's refinement isn't.

Idle isn't as smooth as it should be. Then, around 3000 rpm, there's a period of tingling vibration. And the last 1000 rpm before redline isn't a pleasant thing to hear. To be blunt, the engine falls short of Porsche's elevated standards.

Exactly how high those standards are has been made plain by the 3.6-liter designed by Porsche for the new V-6 version of the Panamera. The European launch of the Cayenne and Panamera V-6s was staged over consecutive days on roads around Cologne, Germany. Driving one, then, next day, the other, was educational to say the least.

Porsche's own engine is smoother and offers greater sonic satisfaction. The Panamera V-6 also feels more snappily responsive, although some credit for that is surely due to its sporty seven-speed double-clutch - PDK in Porsche's lexicon - transmission. The Cayenne's VW-sourced V-6 is teamed with a not-quite-so-sporty conventional automatic with torque convertor. Made by Japanese company Aisin, it's nevertheless a fine transmission. It deserves to be bolted to a better engine.