Result of integrating 720 degrees of pressure diagram

Figure showing power and torque curve out of the engine simulation

The pressure diagram is subsequently integrated over the 720 degrees, giving in a generated torque of the model. The specified mechanical losses are subtracted from this value, resulting in a torque output.

Additionally the simulation model divides the amount of fuel by the power output, supplying an efficiency curve.

Simulation runs till at least rev limiter plus 200 rpm

Figure showing a zoomed area of the engine power and torque characteristic close to the rev limiter

The simulation model will calculate the engine power and torque till at least the specified rev limiter plus 200 rpm.

In the results LapSim shows the maximum power below the rev limiter.

Above the rev limiter, the power and torque lines continue, but their areas do not.

Influences the burn speed of the mixture

Figure showing a zoomed area of the engine power and torque characteristic where the ignition timing is shown

The compression ratio in combination with the selected octane of the fuel, determines the ignition timing.

The ignition timing in the simulation is plotted at the bottom of the torque/power graph, as can be seen in the figure.

Since a higher octane fuel has more resistance to burn, it only increases the engine torque when compression is sufficient high. Otherwise it even causes a power decrease due to the slower burn rate.


With the current trend of going to fuel flow limitations as well as a limited amount of fuel which can be used per lap, we added the option change the overall lambda.

Engines deliver their maximum power with lambda between 0.85 and 0.89. For maximum efficiency, the engine needs to run much leaner.

Determines cylinder volume @ crankshaft degree

Printscreen of the LapSim GUI showing the input engine bore, stroke, capacity, drive rod length and compression ratio

In the main menu you need to specify the global details of your engine. Out of the bore, stroke and amount of cylinders, the software determines total engine displacement.

The drive rod length in combination with the stroke, determines the position of the piston to the crankshaft.

Assumed to be constant, not dependent on rpm

Printscreen of the LapSim GUI where the engine brake torque is specified

The pumping losses of the engine are taken into account due to the 720 degrees pressure diagram. However the mechanical friction losses of the engine still need to be subtracted to get to power output.

The mechanical friction losses are assumed to be constant and not dependent of the engine revs.

Limiting the amount of air entering the engine

Figure showing the engine fill rate out of the simulation, where it can be seen that the air restrictor limits the air flow

Air restrictors are a very effective way of limiting the amount of air entering an engine and thereby limiting the power output.

in the figure you see an example of the fill rate of an engine with an air restrictor. From 6200 [rpm] the restrictor limits the air flow, leading to a steep decline in fill rate.