Operation
Formula One currently uses four-stroke V8, naturally aspirated reciprocating engines. They typically produce 224 kilowatts (300 bhp, 304 PS) per litre of displacement, far higher than most naturally aspirated internal combustion engines.
The power a Formula One engine produces is generated by operating at a very high rotational speed, up to 18,000 revolutions per minute (RPM). This contrasts with road car engines of a similar size which operate safely at typically less than 7,000 rpm. The basic configuration of a naturally aspirated Formula One engine has not been greatly modified since the 1967 Cosworth DFV and the mean effective pressure has stayed at around 14 bar MEP. Until the mid-1980s Formula One engines were limited to around 12,000 rpm due to the traditional metal valve springs used inside the engine to close the valves. The speed required to operate the engine valves at a higher RPM is much greater than the metal valve springs can achieve and they were replaced by pneumatic valve springs introduced by Renault. Since the 1990s, all Formula One engine manufacturers now use pneumatic valve springs with the pressurised air allowing engines to reach speeds of nearly 20,000 rpm.
The bore is the diameter of the cylinder in the engine block, and the stroke is the distance the piston travels from top dead-centre (TDC) to bottom dead-centre (BDC) inside the cylinder. To operate at high engine speeds the stroke must be relatively short to prevent catastrophic failure, usually connecting rod failure as they are under very large stresses at these speeds. Having a short stroke means that a relatively large bore is required to make the 2.4 litre displacement. This results in a less efficient combustion stroke, especially at lower RPM. The stroke of a Formula One engine is approximately 39.7 mm (1.56 in), less than half as long as the bore is wide (98.0 mm) producing an over-square configuration.
In addition to the use of pneumatic valve springs a Formula One engine's high RPM output has been made possible due to advances in metallurgy and design allowing lighter pistons and connecting rods to withstand the accelerations necessary to attain such high speeds, also by narrowing the connecting rod ends allowing for narrower main bearings. This allows for higher RPM with less bearing-damaging heat build-up. For each stroke, the piston goes from a null speed, to almost two times the mean speed, (approx. 40 m/s) then back to zero. This will occur 4 times for each of the 4 strokes in the cycle. Maximum piston acceleration occurs at mid‑stroke and is in the region of 95,000 m/s2, about 10,000 times standard gravity or 10,000 g.
Read more about this topic: Formula One Engines
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