Today’s Wall Street Journal had an interesting article on how Alex Friedrich hired some university engineers to see how carbon-dioxide emissions could be reduced in a VW Golf, their best selling model. They were able to reduce the emissions from 172 grams per kilometer to 120 grams.
The interesting part was what they did to achieve those gains. Nothing was done that reduced the car’s horsepower. They worked on three key aspects: weight, aerodynamics, and rolling resistance.
They cut the vehicle’s weight by 40 kilograms by using a carbon fiber hood and racing style seats. They improved aerodynamics by replacing the rear view mirrors with tiny cameras (a 2% fuel consumption improvement at highway speeds) and lowering the car’s ride height. Rolling resistance was improved by changing the tires and that produced a reduction of 4% in fuel consumption. Other improvements were changes in the gear ratios and shift point lights to let the driver know when to shift for better fuel economy with improvements of 4% and 8% respectively. They also added a very unpopular option – the start-stop feature that stops the engine when the car is waiting at a traffic signal or stop sign.
Cars have become much heavier, even compact cars. Back in 1980 a Ford Fiesta weighed in at about 1800 pounds while today’s focus comes in at over 2600 pounds. A lot of this is because cars have been engineered to be far more crash worthy, and that is certainly a good thing. We cannot forget that it takes more power to move more weight (mass).
Aerodynamics also plays a key role in fuel consumption and performance. Replacing outside rear view mirrors can provide real benefits in those areas, but regulations would need to be changed to accommodate them and that could take a year or two of the various legislating bodies’ time to make the regulatory changes.
I’m not sure how I feel about tires with lower rolling resistance. I know I like the idea of them providing better fuel economy, but I’m not sure that the trade off in performance and safety (stopping distance and handling) would be all that attractive.
What I do like is that Axel was willing to try a low tech approach to the problem of carbon-dioxide emissions. The average for German cars sold in 2006 is 172 grams per kilometer and the target for 2008 is 140 with a much tougher goal of 120 by 2012. Hmm, I wonder what the Ariel Atom does?