As handsome as the new Mercedes-Benz E-Class Cabriolet may be, attention at January's Detroit auto show is certain to focus on a single technological breakthrough, a small wing that extends from its windshield to greatly reduce top-down turbulence.
It's a novel idea. With it, four-seat convertibles' traditional top-down limitations as fair-weather friends and primarily urban cruisers are addressed as never before. The rear seat is rendered comfortable with the top down even at high speeds and in previously unbearable hot or cold weather.
The AirCap, as company marketers call the innovation, performs as an aerodynamic comb-over from the windshield header to beyond the rear seat. Wind flow is deflected above the interior before flowing to trunk level back of the complementary screen between the rear head rests.
Competing luxury manufacturers can be expected to copy this feature as quickly as they can figure out how to cram the necessary hardware into their own windshield headers. Mercedes-Benz, for its part, tinkered with the idea for almost 20 years before beginning work on this iteration in 2005. Nearly 20 patents have been filed.
The top-down trick for convertibles is, was, and always will be providing occupants with the desirable feature of wind blowing in their hair - without threatening to tear it out.
An early step toward calming the interior turmoil was the draft-stop screen behind the seats that premiered in the 1989 Mercedes-Benz SL two-seater and is now common among sports cars.
The AirScarf, which blows warm or cool air at the neck, raised comfort levels still higher when introduced in 2004 in the SLK sportster.
The E-Class Cabriolet employs the AirScarf as a complement to the new AirCap - but, unfortunately, only for front seat occupants. (Inadequate room for neck-level heat channelling in the rear seat is a consequence of the safety bars behind the rear seating that extend when an impending rollover is sensed.)
Still, Mercedes-Benz executives argue that foursomes have never had it so good. "Our market research has shown that most four-seater convertibles are really only suitable as two-seaters in day-to-day use," said Rainer Tiefenbacher, head of project development for this car, "because the draft-stop is often awkward to install and remains in place during the open-top season (limiting rear-seat access)."
As though concerned their claims be considered so much hot air, Mercedes demonstrated the efficacy of their wind deflector in spectacular fashion. Convertibles typically make their press debuts at such sunny retreats as Majorca, Tiefenbacher noted, but the car's extended spring and fall ability would be best demonstrated in a wind tunnel.
No vote was taken among the attending reporters on this matter, understand, but, whatever one's opinion going in, nothing on offer in the Spanish island in the Mediterranean could have equalled the tunnel with its airflow stirred by a seven-metre turbine propeller.
Professor Wunibald Kamm, respected by automobile historians as a pioneer in aerodynamic design, put this tunnel to work in 1939 and it has been updated continuously.
With journalists aboard the top-down E-Class, speeds from 80 km/h to 140 km/h were created by the mad scientist at the controls - Dr. Teddy Woll, senior manager, aerodynamics and wind tunnels. He is both bald and wiry, probably the result of battling strong winds every day of his working life.
We start in the rear seat. A comfy-enough space with just adequate foot and knee room, accessed easily because the front-seat powers back and forth - until we start gaining simulated speed.
With the wind deflector disengaged, so that the aluminum and mesh screen construction withdraws into the windshield header, one is reminded just how uncomfortable a convertible typically becomes at highway speeds. Each and every individual hair is pulled behind you - except for those on the sides of your head that somehow blow straight out. It's cold. The wind roars. Conversation is impossible.
When the scribe in the driver's seat activates the wind deflector so it extends six millimetres, though, calm comes upon us whether at 120 km/h or 140 km/h. Certainly there's some wind evident, far more so than in a closed-top car, but the gain in comfort is undeniable.
"The AirCap creates a warm air bath," Woll said afterward. "Drafts are reduced and warm air flowing from the heater vents remains there for much longer."
The device can be extended at speeds up to 160 km/h, and, once in place, is functional right up to maximum speed or OPP seizure, whichever comes first. Addressing another concern, the responsible engineers dismissed any suggestion that the 211 individual parts at work within the windshield header could fail due to freezing in place in Canadian non-convertible months.
"A double pinch [prevention]is designed into the wind deflector's operation so it cannot close on one's fingers, nor will it attempt opening if it's frozen," said Jorg Bartels, senior manager of AirCap development.
An electric motor only 18 mm in diameter, sourced from a Swiss dental equipment firm, works with a gearbox designed by Benz engineers to activate the deflector up or down and lock it into the windshield pillars.
Innovative as the breakthrough may be, another, more traditional aspect of the car will surprise Detroit show-goers if any of the E-Class convertibles are on exhibit with their tops up. Daimler's decision makers have stuck with the traditional cloth top, ignoring the trend to retracting hard tops with their benefits in sound- and vandal-proofing.
"There are two reasons for the cloth top," Woll said. "One is that we wanted to offer a true cabriolet.
"Secondly, we feel there are severe styling restrictions when folding hard tops are employed on four-seaters. Look at the Peugeot [a comparable model] it's ugly. And the 3 Series BMW looks much nicer as a coupe than as the cabriolet."
The cabriolet will go on sale in Canada in May, as will the wagon version of the E-class.