Design of Direct Injection Jet Ignition High Performance Naturally Aspirated Motorcycle Engines

Thanks to the adoption of high pressure, direct injection and jet ignition, plus electrically assisted turbo-compounding, the fuel conversion efficiency of Fédération Internationale de l’Automobile (FIA) F1 engines has been spectacularly improved up to values above 46% peak power, and 50% peak efficiency, by running lean of stoichiometry stratified in a high boost, high compression ratio environment. Opposite, Federation Internationale de Motocyclisme (FIM) Moto-GP engines are still naturally aspirated, port injected, spark ignited, working with homogeneous mixtures. This old fashioned but highly optimized design is responsible for relatively low fuel conversion efficiencies, and yet delivers an outstanding specific power density of 200 kW/liter. The potential to improve the fuel conversion efficiency of Moto-GP engines through the adoption of direct injection and jet ignition, prevented by the current rules, is herein discussed based on simulations. As two-stroke engines may benefit from direct injection and jet ignition more than four-stroke engines, the opportunity of a return of two-stroke engines is also argued, similarly based on simulations. About the same power, but at a better fuel efficiency, of today’s 1000 cm³ four stroke engines, may be obtained with lean stratified direct injection jet ignition engines, four-stroke of 1450 cm³, or two-stroke of 1050 cm³. About the same power and fuel efficiency may also be delivered with stoichiometric engines direct injection jet ignition two-stroke of 750 cm³.