Burn Rate

Burn Rate refers to the time required for the air/fuel mixture to burn completely (the speed at which fuel releases its energy) with the piston near top dead center of the stroke. The faster the fuel burns, the more efficient the engine and the more power it will generate and the better fuel economy it will get.  Also, engine's with faster burn rates require less spark advance.

The fuel has very little time to release it's energy. The pressure created from burning should be at it's greatest close to 15 degrees after top dead center. If the fuel is not nearly done burning after this point, it is not contributing much power to the engine. If peak pressure occurs too soon, the pressure is "fighting" the piston as it's coming up. If peak pressure occurs much after that, you're not getting the optimum "push" on the piston on the power stroke.

Old race engines required 40 degree or more of spark advance because of the slower burn rates of the engine and chamber designs at the time. A modern, comparable "fast burn" race engine may only need 30 degrees of spark advance for best power.

How does Performance Trends software take Burn Rate into effect?