Comparison Between Two Combustion Chambers for a Motorcycle Racing Engine

An experimental and computational analysis has been performed on the combustion chamber of a two cylinder, four stroke, four valve, spark ignition engine developed by Ducati Motor SpA for the Super Sport Championship. Two cylinder head configurations have been analyzed by using a three dimensional CFD code. Port and valve assemblies do not change. Only the combustion chamber surface changes in order to improve the intake flow. Head flow performances in terms of permeability have been determined by computing the steady discharge coefficients at different valve lifts. These values have also been measured on a steady flow test bench. Head flow performances in terms of flow conditioning, i.e. the attitude to promote tumbling and enhance combustion, have been determined by computing the equivalent solid body tumbling number of the flow field at intake bottom dead center. The modified cylinder head combustion chamber surface produces higher steady discharge coefficients and intake bottom dead center tumbling number. Volumetric efficiency and brake mean effective pressure and specific fuel consumption for the steady, wide open throttle operation of the engine have been measured on a steady engine test bench. The full load test has been also simulated by a one dimensional engine cycle code. This simulation provided further information to integrate experimental results.