Achtung, Bel-Air

EUROPE is on a war footing.

A walk around the sprawling Messe Frankfurt complex, home of the city’s International Auto Show, reveals how deadly serious European regulators are about curbing greenhouse-gas emissions, at least relative to the laissez faire Americans. It also shows how far European carmakers have to go.

Frankfurt is the show where carmakers roll out their autobahn artillery — witness Mercedes-Benz’s eighth-generation S-class sedan and Audi’s enormous Q7 luxury SUV, both unveiled last week at the show, which is held every two years. And yet there is doubt about how these enormous cars, which seem a part of some previous modus vivendi, fit into Europe’s changing regulatory landscape. For example, the European Union has targeted that by 2009, the European new car fleet will have to average something like 40 miles per gallon. It’s virtually climate martial law.

All other things being equal, European manufacturers — particularly global giants such as the VW Group and DaimlerChrysler — would rely on their historic advantages in diesel technology to meet these goals (diesel engines get anywhere from 25% to 40% better fuel economy than gasoline engines). But the EU has ruled out easy answers. Other European requirements in 2010 will force huge cuts in diesel particulate and nitrides of oxygen (NOx) emissions. Meeting those provisions may all but eliminate the economy advantages of diesel powertrains. About the same time, new standards for occupant and pedestrian safety will add more weight to cars and proscribe more aerodynamically efficient designs.

This is herding European manufacturers toward the one propulsion technology that they have most disdained: hybrids. It’s with no small sense of exasperation that the Europeans are conceding on this technological point, where they have been outflanked by Japanese manufacturers, particularly Toyota and Honda.

The results, seen on the turnstiles in Frankfurt, amount to technological shotgun marriages. Mercedes-Benz, for instance, unveiled its new S-class sedan accompanied by two hybrid concepts, one gasoline and one diesel, both with a small start-stop motor integrated into the powertrain. The S350 Direct Hybrid with a direct-injection gasoline engine produces 300 horsepower and gets 28.3 mph combined mileage. The S320 Bluetec Hybrid, with a diesel engine, summons 243 horsepower and a massive 424 pound-feet of torque while returning 30.5 combined mpg, the company says.

Audi’s world premiere of the Q7 also included a hybrid concept design. BMW likewise unveiled a mild-hybrid concept of its X3 SUV, using super-capacitors nestled in the doors for energy storage, instead of heavier nickel-metal hydride or lithium-ion batteries. Each of these concepts could be production-ready within three years.

BMW — which, like General Motors, has a lot of equity in the future of hydrogen fuel-cell technology — continues to tout its plans for a hydrogen-powered international combustion engine, but these proposals seem increasingly fanciful in light of the obdurate economics of hydrogen supply, infrastructure and overall efficiency, the total energy costs from oil well to car wheel. As a bit of bet hedging, BMW this month joined GM and DaimlerChrysler in a program to develop hybrids.

SPEAKING of efficiency, I wonder if it wouldn’t be easier to hold the Frankfurt show at the Staples Center. Many of the cars unveiled have their primary audience half a world away. Bentley revealed its next-generation Azure, a Bel Air-intensive cabriolet based on the current Arnage. The Azure is a $300,000 blunderbuss powered by a 6.8-liter turbocharged V8. Bentley calls it the marque’s “statement car� — I will entertain all suggestions as to what statement it makes. Nearby, Bentley’s VW Group cousin Lamborghini displayed the Gallardo Spyder, which will fish for Wilshire moguls alongside the Ferrari F430 Spider.

The Mercedes-Benz S-class is bigger and grander than the car it replaces and bristles with the company’s latest safety innovations, including range-finding automatic brake-assist, all-speed adaptive cruise control, infrared night vision and a variety of other measures it calls Pre-Safe technology. The Benz is just one of several cars that advance automated driving assistance — everything from blind-spot detection to automatic lane keeping.

The BMW Z4 and the Porsche Boxster, two of L.A.’s favorite heliocentric roadsters, will get hardtops with the Z4 coupe and the Porsche Cayman S. The hardtop version of the Z4 dramatically redefines — and improves — the original Chris Bangle design, which always looked to me like a salamander with a broken tail. The slick-backed Z4 will be offered with a 3.0-liter, 260-horsepower inline six or the M3’s high-performance 3.2-liter, 360-horsepower I-6. The Cayman S was one of the show’s unqualified hits, a lean, haunch-heavy coupe with handsome gills feeding air to a 295-horsepower, 3.4-liter boxer six engine amidships. Priced at about $60,000, the car poses a cannibalizing threat to big brother 911. I have it from an insider at Porsche that the company actually had to dial the power back so the mid-engine car would not overtake the rear-engined icon.

Jaguar pulled the silk off its next generation XK, an all-aluminum coupe and roadster pair powered by the company’s 4.2-liter, 300-horsepower V8 and coupled with a six-speed manual-shift automatic. Sleek and muscular — although saddled with a rather indifferent nose cone — the car is an exceptional piece of structural engineering, with interior refinement rivaling anything in its class. If Jag is going to survive, this is as good a place as any to start.

On the smaller end of things, Mini revealed its Mini Traveller station wagon concept vehicle. About 8 inches longer than the current Mini, the Traveller will be one of several new body styles Mini will offer to expand the brand in the U.S. and Europe beginning next year. Honda, meanwhile, displayed its European variant of the new Civic five-door hatch, which is a marvel of space efficiency inside a wide, sweeping and taut body. However, this gorgeous car, one of my favorites at the show, will not be available in the U.S.

ONE of the most stubborn problems in car design has been the convertible top: In its canvas variety, it can be noisy and visually graceless, while the retractable hardtop style can be heavy and space-consuming. But three new cars, all four-seat, full-size cabriolets, showed the aesthetic promise of advanced retractable hardtops: the VW Eos (based on the Passat platform), the Volvo C70 (platform-mate of the S40 and V50) and the Opel Astra TwinTop. Each of these cars has an exquisitely engineered three-section roof that separates into discreet panels that shuffle together like playing cards before disappearing beneath the motorized flush tonneau cover. These pliant mechanisms preserve the usable space inside the boot of the car, enough to hold two golf bags with the top down. The VW and the Volvo, with prices estimated at $32,000 and $42,000, respectively, will go on sale in the U.S. next year. Both look like perfect California cars.

And then there’s the car I want. Every time I go to one of these European shows, I fall in love with a car not for sale in the U.S. This time, it’s the Citroën C6, a gorgeous, low lozenge of a car, a big five-seat saloon with a sleek, stubborn Gallic contempt for convention, from its concave rear glass to its luxurious front overhang. The interior is a tone-perfect execution of modernistic shapes rendered in classic luxury surfaces.

I’m not usually an advocate of badge engineering, but if GM wants to slap a Cadillac crest on this car and sell it in the U.S., I’ll take one in Le Mans blue.