The different heat release properties will suite different engine characteristics and should be orchestred with the actual exhaust port height, which decides the opening pressure, i.e. The engine stress and detonation risk would also increase with the higher peak.
This means that a low rpm engine will produce less power with the fast burning fuel and visa versa. (A1 and A2)Ī high pressure peak for a short time might produce less work than a low peak for a long time at a certain rpm. If the pressure on the piston varies as in the picture at a certain rpm, the area below the curve could represent the work. The resulting power output will be an integral of crank moment over time. (Pressure in MPa creates an additional piston force) As a schedule example, if fuelblend 1 releases most of the energy in a very short time after TDC with a high pressure peak and blend 2 in a longer period of time with a moderate pressure peak then the moment on the crank will be different over the time for the two cases. The picture shows the relationship to crank angle and crank moment. 50% of the available heat is usually released within 5° -10° ATDC (After Top Dead Center). During the combustion, the molecules break down step by step with different heat release at each step. The fuel ratio of H/C (hydrogen/carbon) in the CnHm molecules varies, n and m takes certain values for different fuels. The heat release time from combustion is mainly decided from the fuel properties, air/fuel ratio and cylinder head design. A well designed fuel is an important factor to race engines. The process can be described with these steps:Īt this point the fuel property will decide the heat release, at which time the fuel will produce work. The charging efficiency is dependent on the pulse energy created from the cylinder pressure at exhaust port opening.
This is an important process to understand and is the reason why not only the cylinder decides the tuning degree but also the exhaust pipe, cylinder head and ignition.
The high performance 2-stroke engine is a pulse resonance engine which means that the operation in general and the scavenging in particular is not only dependent upon the pulses created from piston pumping but also from combustion properties.
Two stroke performance tuning software#
This section describes the basic function and the most important processes in the 2-stroke cycle a tuner need to consider in general and with the Bimotion tuning software in particular.
Two stroke performance tuning mods#
Two Stroke Engine Porting, Head Mods and Pipes Two Stroke Tuning Advice From The experts at Bimotion
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