"It has come to the point where acceleration equals consumption," said Stephan Winkelmann, CEO of the Italian automaker. "More consumption means increased CO2 emissions."

Winkelmann, who fears future government regulations could restrict engine performance, said Lamborghini's r&d spending will emphasize taking weight out of vehicles.

The pursuit of top speed is limited by the physics of aerodynamic resistance, Maurizio Reggiani, Lamborghini's r&d chief, said in an interview this month at the Detroit auto show. Once a vehicle reaches 211 mph, there is a declining rate of return for each additional horsepower needed to push the vehicle faster, he said.

Also, there are few places in the world where a driver can go that fast. So Reggiani said Lamborghini will focus on acceleration instead of top speed. The most effective way to do that, he said: take weight out of the car.

"The weight-to-power ratio will be the key factor," Reggiani said. "We will use composite materials in the right place, when it also has the right cost, stiffness and mechanical characteristics."

That could prove to be an expensive solution. Lamborghini has used mostly high-strength steel in its vehicles' structures and body panels. But Reggiani said the automaker will make greater use of aluminum and carbon fiber.

Lamborghini has made progress with its re-engineered Murcielago LP670-4 SV. The new version of the car has added 30 hp while shedding 220 pounds, mostly through use of carbon fiber. The "670" in the car's name reflects its horsepower rating. The car can reach 62 mph in 3.2 seconds.

"No one can really tell 30 horsepower was added, but everyone can feel how much lighter the car is," Reggiani said.

Lamborghini also is investigating start-stop technology for city driving to reduce emissions of carbon dioxide. But with a V10 or V12 engine, the firing order is faster than a typical four-cylinder with start-stop.

As a result, Reggiani said, missing a cylinder or two on vehicle restart could cause more pollution than not having the technology at all. The same theory applies to cylinder deactivation at cruising speeds.

"Where is the supplier who can provide the right starter and alternator for our engine?" Reggiani asked. "That's a lot of cylinders. It's easy to make a mistake."