Improving the Fuel Economy of a Tuned 600cc FSAE Engine

To maintain its relevance, motorsport cannot be exempt from<br/>the trend of increasing fuel economy. This bears obvious<br/>competitive benefits as well, either in decreasing the<br/>frequency of pit stops or the mass of fuel carried. Given the<br/>increased points weighting of fuel economy for the Formula<br/>Student (FS) competition, a complete analysis was performed<br/>on the Queen's Formula Racing 600cc motorcycle engine in<br/>preparation for the 2011 competition.<br/>The criteria for such high performance fuel economy differ to<br/>a degree from most mass transportation counterparts and were<br/>divided into three distinct regimes; full load, part load and no<br/>load conditions.<br/>Full load positions naturally demand maximum torque for<br/>performance but that does not imply that fuel savings cannot<br/>be made whilst preserving this. The point at which maximum<br/>torque is produced with minimum air -fuel ratio, Leanest<br/>mixture for Best Torque (LBT), was therefore sought and<br/>mapped for full load.<br/>At part load, torque is less of a concern, and maintaining a<br/>sustainable engine temperature and transient response become<br/>more important. With decreasing AFR, engine temperatures<br/>can rise dramatically so temperatures were measured close to<br/>the exhaust port for a wide range of air-fuel ratios.<br/>Competition track data was analysed to highlight key part load<br/>operating regions and these were mapped according to<br/>measured safe temperature limits. Torque response to a step<br/>throttle change was also measured to ensure suitable engine<br/>transient performance was maintained.<br/>At no load conditions, with low engine speed only idle<br/>conditions need to be satisfied. In the situation where the<br/>engine is still at high speed without load, the engine is being<br/>motored and no fuel is required. An overrun fuel cut was<br/>employed to reflect this giving significant fuel savings. The<br/>effect on torque and engine pickup was measured.<br/>Modifications were also made to the fuel injector location to<br/>improve fuel mixing and evaporation at this lower air flow<br/>condition.<br/>These mapping regimes were implemented and tested using<br/>fully transient lap simulations using competition track data<br/>and a four quadrant AC engine dynamometer. The experiment<br/>indicated a reduction in fuel consumption for 22 laps of the FS<br/>track from 5.08litres to 3.67litres, around 27% in total. The<br/>actual fuel used at the 2011 competition was 3.6 litres while<br/>placing 8th in the endurance event, further validating the<br/>benefits of these mapping regimes.