In an engine cylinder, the rate of pressure rise following ignition is generally kept below Harry Ricardo’s advised maximum: 40 psi per crank degree. Rates higher than that, he observed, led to noise, harshness, or parts damage (an example of very high rate of pressure rise is detonation, which readily damages bearings). As an example, consider a well-developed racing engine with a peak combustion pressure of 1,200 psi. If it ignites its charge at 35 degrees BTDC and peaks at the desirable 11 ATDC, that is a total of 46 crank degrees. This gives as rate of pressure rise 1,200 divided by 46 equals 26 psi per crank degree.