Improving the Fuel Economy of a Tuned 600cc FSAE Engine 2012-32-0027
To maintain its relevance, motorsport cannot be exempt from the trend of increasing fuel economy. This bears obvious competitive benefits as well, either in decreasing the frequency of pit stops or the mass of fuel carried. Given the increased points weighting of fuel economy for the Formula Student (FS) competition, a complete analysis was performed on the Queen's Formula Racing 600cc motorcycle engine in preparation for the 2011 competition.
The criteria for such high performance fuel economy differ to a degree from most mass transportation counterparts and were divided into three distinct regimes; full load, part load and no load conditions.
Full load conditions naturally demand maximum torque for performance but that does not imply that fuel savings cannot be made whilst preserving this. The point at which maximum torque is produced with minimum air-fuel ratio, Leanest mixture for Best Torque (LBT), was therefore sought and mapped for full load.
At part load, torque is less of a concern, and maintaining a sustainable engine temperature and transient response become more important. With increasing AFR, engine temperatures can rise dramatically so temperatures were measured close to the exhaust port for a wide range of air-fuel ratios. Competition track data was analysed to highlight key part load operating regions and these were mapped to minimize any increase in operating temperature. Torque response to a step throttle change was also measured to ensure suitable engine transient performance was maintained.
In the situation where the engine is still at high speed without load, the engine is being motored and no fuel is required. An overrun fuel cut was employed to reflect this giving significant fuel savings. The effect on torque and engine pickup was measured.
These mapping regimes were implemented and tested using fully transient lap simulations using competition track data and a four quadrant AC engine dynamometer. The results indicated a reduction in fuel consumption for 22 laps of the FS track from 5.08 litres to 3.76 litres; around 26% in total. The actual fuel used at the 2011 competition was 3.702 litres while placing 8th in the endurance event, further validating the benefits of these mapping regimes.