Flexfuel
Changing the Way Our Cars are Powered Not the Way They Perform
At the 2008 Geneva Auto Salon, Bentley announced a far-reaching environmental programme to reduce CO2 emissions and improve fuel economy across the Bentley range. A continuation of our commitment to minimise impact both locally and globally.
Stage One of the strategy, ‘Efficiency’, will cut tailpipe emissions and fuel consumption by 15 per cent by 2012. This will be achieved through reduced weight and a number of engine enhancements. The second, more fundamental stage, is to make the entire Bentley fleet capable of running on renewable fuel through the introduction of FlexFuel technology. Where engines are capable of running seamlessly on bioethanol, gasoline or a mix of the two. These will be introduced progressively throughout the Bentley range.
At the same time we declared that this would be achieved without sacrificing Bentley’s reputation for performance and luxury. This statement of intent has taken shape in the Continental Supersports. A car that balances extreme potency with pioneering use of biofuel technology in the luxury sector. The result is our fastest, most powerful Bentley ever and our most efficient. A car capable of reducing net CO2 by up to 70% on a ‘well to wheel’ basis.
Creating an Unbroken Energy Cycle
Either Bioethanol or gasoline can be used to power the Continental Supersports.
Bioethanol is often blended with gasoline in a variety of percentages ranging from E10 (10% bioethanol) to the most widely known, E85, blended at a ratio of 85% bioethanol to 15% gasoline. Bioethanol E85 can offer up to 70% net CO2 reduction on a ‘well to wheel’ basis – a value that is calculated by adding the CO2 emitted during the refining process (‘well’) with the CO2 released when the fuel is burned (‘wheel’).
Bioethanol can be responsibly derived from crops such as corn, soybeans, sugar and switchgrass. Second generation bioethanol uses the non-food fibres of the plant (biomass), as well as gricultural waste and forestry residues. These would be collected and refined into cellulose ethanol then blended with gasoline to power biofuel vehicles.
CO2 is absorbed by plants as part of the photosynthesis process and cars using Biofuel then release that CO2 back into the atmosphere, thus creating an unbroken energy cycle.
In addition, biofuels are not derived from fossil fuels, making them a renewable resource ensuring a secure supply into the future.
The diagram below illustrates how Biofuel is created and explains the unbroken energy cycle.
The System Balances Lower Emissions with a Bentley Driving Experience
Crewe engineers have equipped the W12, 6-litre power unit of the Continental Supersports with the technology to run on gasoline or a mix of gasoline and bioethanol, all in one fuel tank.
A sensor in the fuel supply circuit detects the blending ratio of the fuel in real time sending a signal to the Engine Control Unit. The unit then instantly initiates the correct engine mapping to ensure all performance parameters remain totally balanced and consistent.
Power, torque and emissions remain at constant levels whatever the ratio of gasoline to bioethanol.
Engineering a FlexFuel Car
Engineering a FlexFuel car is not a simple matter given the complexity of our engine management systems and emissions equipment. It involves:
- Recalibration of the engine management.
- A Full calibration programme for both petrol and E85
- Running extensive engine dynamometer tests.
- Numerous 100,000km complete vehicle durability cycles.
- Trials in hot and cold climates.
- Validation for all fuel ratios of ethanol from 0 to 85%.
Biofuels
The concept behind biofuels relies on the CO2 consumed during the growth of a bio-fuel crop, which is later released at the point of combustion.
First Generation Biofuels
Are largely derived from the fruit or grain of the plant. Cultivation can compete with food production. When produced in a sustainable manner, first generation biofuels still represent an important step in the right direction. Large amounts of such biofuels are being produced in countries such as Brazil, where the CO2 balance is extremely positive.
Second Generation Biofuels
Are produced from agricultural residue and waste materials (biomass), and have a high yield per unit area. Such fuels have the potential to reduce CO2 emissions by up to 90 per cent. The sustainable nature of second generation biofuels means that they do not compete with food production, nor do they require destruction of natural habitats to expand.
Third Generation Biofuels
Third generation bioethanol can be produced using intensively farmed algae. Currently, production methods are in their infancy.
Biomass
Covers a wide range of organic material from crops such as corn, soybeans, sugar and switchgrass, as well as agricultural waste and forestry residues. It also includes landfill and municipal solid waste. Biomass can be used for conversion into liquid fuels, such as bioethanol, biomethanol, biodiesel and also electricity and hydrogen.
FlexFuel
(Also known as FFV, flexible-fuel or dual-fuel) describes engine technology which enables vehicles to run on any mix of gasoline and bioethanol. A sensor in the fuel supply circuit detects the blending ratio of the fuel. FlexFuel systems can run on biofuels where available, gasoline where not, or on any mix of the two.
Well To Wheel
Is the widely accepted measure of energy efficiency and has been defined by European Commission advisers as ‘the integration of all steps required to produce and distribute a fuel (starting from the primary energy resource) and use it in a vehicle’.
Lignocellulose
Is material found in the stalks of crop waste and can be utilised to provide the biomass required for bioethanol production, a second generation biofuel.
Bioethanol (First Generation)
Can be used as a gasoline replacement in FlexFuel cars and is sold as E85 (85% Bioethanol, 15% Gasoline). It offers net CO2 reduction of between 50 – 80% on a ‘Well to Wheel’ basis.
Biodiesel (First Generation)
Is manufactured from renewable raw materials, often food crops. It can be blended with diesel (Biodiesel 10%, Diesel 90%) and used in diesel cars.
Cellulose Ethanol (Second Generation)
A biofuel for use in FlexFuel engines as a gasoline replacement. Its advantage is that it uses biomass, such as crop waste, as the raw material. It offers consistently high CO2 reductions of 90% on a ‘well to wheel’ basis, whilst remaining sustainable.
Biomass-To-Liquid (BTL) (Second Generation)
Is a bio-fuel aimed at replacing diesel through an advanced process utilizing biomass as the raw materials. It offers consistently high CO2 reductions of 90% on a ‘well to wheel’ basis.