The third-generation Porsche Boxster is now just four months away from a planned debut at next year’s Geneva motor show. But before the German car maker’s boss Mathias Muller granted the mid-engined roadster a definitive production go-ahead back in October, Autocar joined a team of development engineers in California as they put the final test miles on prototype versions.

Codenamed 981, the new Boxster represents a big break, both in terms of engineering and philosophy, from its predecessor. Following on from developments brought to the latest 911, the strict two-seater is not only larger dimensionally but also sports an aluminium bodyshell that is claimed to be the “the lightest car in its class,” according to Boxster development boss Hans-Jürgen Wӧhler.

From the very first glimpse of Porsche's third-generation Boxster parked up against a wall in a dimly lit garage somewhere in downtown San Francisco, we find ourselves wondering. Not so much about how it will look when the camouflage is removed and the new car is finally revealed at next year's Geneva auto show. No, the primary thought occupying our mind centers around whether the new roadster, which is planned to go on sale in North America next May, can possibly match the lofty on-road qualities established by its 8-year-old predecessor. As anyone with a current-model Boxster will attest, this new one has a lot to live up to.

It's early morning, and as the city by the bay awakens under a layer of autumnal fog we're anxiously waiting to join the Porsche test and development team for what is being billed as the final shakedown of the new Boxster, which carries the internal code name 981, before it is given a definitive green light for production. Our destination is Los Angeles — a distance of about 600 miles on the route we're set to follow for the next day or so.

Still a Boxster

Even wearing the taped disguise and body cladding, the 2013 Porsche Boxster Prototype seems very close to the old model, the 987, in the looks department. But don't let first appearances fool you. The evolutionary theme evident in the first two generations of the midengine two-seater has apparently given way to a more progressive approach aimed at providing the new model with truly fresh appeal. In other words, it looks tough, not svelte.

As Hans-Jurgen Wohler, the project leader of the new car confirms before we get under way, almost everything has changed. "We have really taken a big step this time around. The changes go deeper than we've ever made to the Boxster over the years — and that also applies to the way it looks."

We will get to know the new roadster a lot better in early 2012 when Porsche divulges official photographs and some more specific details. But for now we can reveal it has grown, if only marginally, in both length and width, while a new automatic roof structure no longer requires manual attachment. It's also slightly shorter than its immediate predecessor.

Following the 911

One change that is clearly obvious when you see it up close is the adoption of larger wheel houses. They're designed to accommodate standard 18-inch wheels, with 19-inch alloys among a long list of options, giving the new Boxster an even more voluptuous silhouette.

With a body made predominantly of aluminum, it is now lighter than before. "If we had continued with steel, it would have ended up being much heavier. And clearly that's not something we wanted. From very early in the development phase we decided the new model would get a high percentage of aluminum," Wohler says.

In keeping with the changes made to the latest 911, with which the 2013 Porsche Boxster Prototype continues to share much of its front end structure, it also rides on a longer wheelbase and runs a considerably wider front track....