21 January 2003
When the rally design teams at SCi and Warfhog Sweden first created the concept for Richard Burns Rally, our goal was to develop the most realistic rally simulator to hit the gaming market to date.
We wanted to move on from the rather static way of simulating engines with predetermined torque curves which seems the norm today, and to create instead an engine model that would react as dynamically to user input and ambient conditions as its real counterpart.
One big advantage of using a detailed simulation model like this is the response to damage. With pre-determined torque curves, there is no good solution to the damage problem. But our model is heavily dependent on the state of its working components. If, say, a turbo on one of our cars is damaged, it will result in lower inlet pressure, and thus less power. We can model misfiring cylinders by simply not igniting the fuel.
The 'four-stroke-Otto-cycle' works like this: The piston starts at the top dead centre (TDC), with the inlet valves being open. As the piston moves down, the cylinder volume will increase and the fuel and air mixture will be sucked into the cylinder. The piston reaches the bottom dead centre (BDC) and sometime around here the inlet valve will close. The piston starts moving up again and the mixture is compressed. At some preset crank angle the fuel is ignited and starts to burn, heat is released and the cylinder pressure increases. This process continues well into the expansion stroke. Finally, when the piston approaches the BDC again, the exhaust valve opens and the burnt gasses are pushed out of the cylinder during the exhaust stroke.
The whole idea is to have a greater mean pressure in the cylinder during the expansion stroke than on the compression stroke and thereby extracting some mechanical work from the process.
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