This paper presents a project undertaken by Ricardo and the Energy Efficient Motorsport (EEMS) working group in the UK. The purpose of this project is to develop a method to encourage fuel efficiency in motorsport and enable vehicles running different types of fuels to race on a competitive basis without having to set up a complex set of rules for every application and while maintaining exciting racing for both teams and spectators.Motorsport technologies typically focus on maximum vehicle performance as their prime criteria for optimisation. In this respect they have begun to diverge from the primary technological goal of road car development, which is now focussed around improvement of efficiency and fuel economy. In this paper, a method is proposed whereby the two goals can be combined, allowing technology flow between road cars and racing cars, making participation more attractive for vehicle manufacturers and at the same time improving the environmental credentials of motor racing.The basis of the proposed method is to cap the instantaneous fuel flow energy to the engine to a maximum value. In this way the race car developers are encouraged to improve the efficiency of the powertrain in order to extract the maximum useable power from the amount of fuel allowed.A method of implementation was found in the form of an inline fuel flow meter that allows monitoring of fuel flow to the engine. Vehicles will need to be recalibrated to run to a fuel flow limit instead of an air flow limit imposed by an air restrictor used in most race series today.Fuel flow limits can be defined for various fuels based on the net heat of combustion of the fuel, so that all vehicles racing in one series have the same maximum energy flow to the engine regardless of fuels used.A system to monitor fuel flow was designed and tested in 2005 on a British Touring Car Championship (BTCC) vehicle running a mixture of ethanol and gasoline. The system consists of an inline turbine flow meter measuring volumetric fuel flow. Measured fuel flow was validated against fuel injection data from the ECU and showed a good correlation.