A crucial concept in engine tuning is the relationship between compression pressure (which is affected by the throttle plate) and ignition timing. This is vital for maximizing power and efficiency while preventing engine knock. ​Compression Pressure vs. Throttle Plate ​The static compression ratio of an engine is a fixed, mechanical property determined by the volume of the cylinder at its largest point (piston at Bottom Dead Center or BDC) versus its smallest point (piston at Top Dead Center or