From an aerodynamic standpoint, the all-new 2006 Dodge Viper SRT10 Coupe is designed for increased downforce and high-speed stability, with a sloping roofline and decklid spoiler. The canopy and rear spoiler of the SRT10 Coupe contributes to more downforce at the rear. It is estimated that the coefficient of drag for the 2006 Dodge SRT10 Coupe will be improved (estimated for Coupe at .39 - the convertible’s coefficient of drag is 0.4).
Gen 2 from dodge viper central
Drag Coefficient 0.495 (top off)
0.46 (soft top)
0.45 (hard top) - RT/10
0.35 - GTS
I can see a big top speed difference in the Gen 2.
It can't be that big a gap in the gen 3. I guess we will never know for sure.
http://en.wikipedia.org/wiki/Drag_coefficient
From Automobile Magazine.
As you can see from the photos, the coupe has the same front end and doors as the roadster. "Even the windshield surround is the same," says Knott. "With ASC's help, we were able to build a coupe on the convertible's foundation. The coupe top, rear quarter-panels, rear fascia, and deck lid are all attached on the current structure." Knott says that the coupe has 30 percent greater structural rigidity than the roadster and that rear downforce has increased significantly thanks to the more aggressive rear spoiler. Although the coupe looks more slippery, it's unlikely that top speed will increase, because the frontal area of the car is slightly larger.
Car and Driver.
its aero advantage should be a single digit, 0.39 Cd versus 0.40. It's expected to weigh in about 15 pounds heavier than the softtop car, and output numbers for the pushrod aluminum V-10 engine will be unchanged
From engineering point of view, the Viper Coupe did not improve from the roadster as much as the legendary GTS did. You might remember the old car was launch as a mid-life update of the Viper, thus it brought a lot of chassis improvement and significant increase of horsepower. In contrast, the Viper Coupe has its entire powertrain untouched. The only thing it improved is a slightly stiffer chassis (thanks to the fixed roof) and slight reduction of aerodynamic drag, from 0.40 to 0.39, though that figure is nothing to be proud of. More welcome is a bigger rear spoiler, which generates 45 kg of downforce at 150 mph. Well, that's not a big number, but at least better than none.
Viper engineers also invested about 1000 hours in wind-tunnel testing. Starting with knowledge gleaned from the racing Viper coupe, the goal was positive downforce at 150 mph to stabilize high-speed handling. A full-length underbody panel was too heavy and trapped too much heat, so the final design is a partial belly pan with what Helbig calls "under-car tricks." Strakes (vertical ribs hanging low in back) help straighten air flow and augment the downforce generated by designer Osamu Shikado's high-riding deck-lid lip. Louvers ahead of the windshield and openings slashed into the flanks relieve underhood heat and air pressure. Final lift and drag figures aren't available, but Helbig expects excellent stability, a slightly reduced drag coefficient, and about the same drag area (the Cd multiplied by the car's frontal area) as in the first-generation Viper.
http://www.ejourney.com/~srwassoc/Engineering/engineering.shtml
http://www.daimlerchrysler.com/dccom/0-5-7182-1-9379-1-0-0-0-0-0-8668-7165-0-0-0-0-0-0-0.html
Osamu Shikado, Design Manager, Advance Product Design
Credited with the exterior of both the 1998 Chrysler Chronos and 1999 Chrysler Citadel concept vehicles, Osamu Shikado debuted his first-ever two-door car just two years ago. It was the 2000 Dodge Viper GTS/R concept car. At the same time Shikado was in the middle of the development of the 2003 Dodge Viper SRT-10.
Osaka, Japan - born Shikado (47) has been with the Chrysler Group Design Studios since 1994. He is married, has two children and now holds the job of Design Manager in Chrysler Group's Advance Product Design Studio in Auburn Hills, Mich.
2003 DODGE VIPER SRT-10 EXTERIOR DESIGN,
as told by Osamu Shikado
"When I look at the original Viper, the most important design cues are the two massive elements which interlocked at the middle of the body. The original Viper has distinctive characteristics, but from some angles it looks cartoonish.
"I added some crease lines on the body surface. It is the strongest departure from the very rounded original one. My intention was to make it appear to have been sculpted out of solid metal, representing strength and power.
"To enhance the new Viper's muscular form, we gave the body a strong profile with higher belt line, dramatic side gill and a 'bump-up' rear fender shape.
"A lower hood incorporates a larger grille opening - boasting an even bolder version of the Dodge-signature cross-hair design - and adds integrated engine louvers for effective airflow in the engine compartment.
"The rear wheels were moved back 2.6 inches and the A-pillar was pulled three inches forward to allow for bigger doors and for improved ingress and egress.
"I like the rear three-quarter view. It looks like some kind of predator set to capture the prey."
The Design Process
"In the beginning, there were 20 or more designers involved in the sketching process. Six of the sketches were picked and turned into scale models.
"The sketches were picked two weeks after the assignment, so we quickly could look at scale models. After several weeks we debuted these to (then DaimlerChrysler Executive Vice President - Product Development and Design) Tom Gale and Trevor Creed. The decision was made to narrow down the themes to two full-size clay models which were fabricated into full-size fiberglass models.
"My model had an evolutionary Viper look, similar to what you see in the 2003 Dodge Viper SRT-10. The other model still had 'Viperness', but was a radical departure from the original Viper. Ultimately, we decided against this over-the-top change."
Aerodynamic Tuning
"We were challenged several times to change some design details for aerodynamics. We spent a lot of time in the DC-Auburn Hills wind tunnel with a 3/8-scale model. Next we took the full-scale model to a place near Stuttgart called FKFS (Forschungsinstitut fur Kraftfahrwesen und Fahrzeugmotoren Stuttgart) where they have a full-scale wind tunnel.
"We tried to figure out what was the best design for the floorpan, and also what the optimum rear decklid height was. We looked at several other elements, such as a separate rear spoiler and the diffuser on the rear fascia.
"The rear end is the thing we had to work on and change the most. The front of the body required very little tuning for engineering feasibility. For example, headlamps were packaged into a tight and very short front overhang. Also the rear fenders, rear decklid and rear fascia were optimized a couple of times for aerodynamic reasons such as the reduction of Cd (coefficient of drag) and the increase of downforce on the rear wheels.
"The reason we picked the FKFS wind tunnel is that it has a rolling road bed - a moving belt - so we could see the effect of aerodynamics on a driving vehicle. We could see the airflow over and under the body. We found out that the new aerodynamics were very effective, with a seven percent reduction in drag over the previous Viper roadster."
