As a rule of thumb, combustion in a piston engine is pretty much centered on TDC. If for best torque we need to set the ignition to spark at 35 degrees BTDC, then combustion continues for roughly the same time after TDC, making the whole combustion event about 70 degrees. At 10,000 rpm, this is roughly 0.001 second. Although people casually refer to combustion in engines as “an explosion,” it is not. It is smooth progressive burning at a low speed of 50 to 150 feet per second. By contrast, dynamite reacts at 8,800 fps and more modern explosives such as PBX or HMX combust at nearly 30,000 fps.