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Main article: 4-stroke engine
Diagram showing the operation of a 4-stroke SI engine. Labels:
1 ? Induction
2 ? Compression
3 ? Power
4 ? Exhaust
The top dead center (TDC) of a piston is the position where it is nearest to the valves; bottom dead center (BDC) is the opposite position where it is furthest from them. A stroke is the movement of a piston from TDC to BDC or vice versa together with the associated process. While an engine is in operation the crankshaft rotates continuously at a nearly constant speed. In a 4-stroke ICE each piston experiences 2 strokes per crankshaft revolution in the following order. Starting the description at TDC, these are:78
Eisenhuth Horseless Vehicle Company
In 1879, Nikolaus Otto manufactured and sold a double expansion engine (the double and triple expansion principles had ample usage in steam engines), with two small cylinders at both sides of a low-pressure larger cylinder, where a second expansion of exhaust stroke gas took place; the owner returned it, alleging poor performance. In 1906, the concept was incorporated in a car built by EHV (Eisenhuth Horseless Vehicle Company) CT, USA;22 and in the 21st century Ilmor designed and successfully tested a 5-stroke double expansion internal combustion engine, with high power output and low SFC (Specific Fuel Consumption).23
The six-stroke engine was invented in 1883. Four kinds of six-stroke use a regular piston in a regular cylinder (Griffin six-stroke, Bajulaz six-stroke, Velozeta six-stroke and Crower six-stroke), firing every three crankshaft revolutions. The systems capture the wasted heat of the four-stroke Otto cycle with an injection of air or water.
The Beare Head and "piston charger" engines operate as opposed-piston engines, two pistons in a single cylinder, firing every two revolutions rather more like a regular four-stroke.
Safety and car - Wikipedia
Road traffic accidents are the largest cause of injury-related deaths worldwide.6 Mary Ward became one of the first documented car fatalities in 1869 in Parsonstown, Ireland,43 and Henry Bliss one of the United States' first pedestrian car casualties in 1899 in New York City.44 There are now standard tests for safety in new cars, such as the EuroNCAP and the US NCAP tests,45 and insurance-industry-backed tests by the Insurance Institute for Highway Safety (IIHS).46
Worldwide, road traffic is becoming ever safer, in part due to efforts by the government to implement safety features in cars (e.g., seat belts, air bags, etc.), reduce unsafe driving practices (e.g., speeding, drinking and driving and texting and driving) and make road design more safe by adding features such as speed bumps, which reduce vehicle speed, and roundabouts, which reduce the likelihood of a head-on-collision (as compared with an intersection).