Pneumatic valve springs

Pneumatic valve springs are metal bellows filled with compressed airCitation
last = Scarborough
first = Craig
author-link =
last2 =
first2 =
author2-link =
title = F1 Engines _ Valve technology
date =
year =
url = http://scarbsf1.com/valves.html
accessdate = 2007-03-05 ] occupying roughly the same space of metal springs used to close valves in high-speed internal combustion engines. This system was introduced in the mid-1980s in Renault turbocharged 1.5 litre Formula 1 engines.

Reducing the number of moving parts that can fail is good engineering. Racing engines often failed at high speeds because mechanical springs were unable to close valves fast enough, leading to engine failure when pistons struck partially opened valves. Renault's innovation was to replace steel springs with light weight compressed air bellows that could respond more quickly and reduce the possibility of valve crashes, other than from leaking bellows. Additionally, the amount of seat tension required to keep a coil sprung valve under control results in peak lift loading drastically higher, with added stress to the entire valvetrain as a result. Pneumatic systems, sharing a common reservoir of pressure retain a more static level of force, controlling the valve effectively, without any attendant peak lift load increase. To avoid bellows failures, air springs are replaced often.

Pneumatic valve springs gave Renault an advantage with its turbocharged engines, often said to be the most powerful. However, reliability and poor handling of their chassis kept the cars from success until 1989 when Renault provided Williams with its V10 engine to begin a winning streak. Renault won the constructors' championship with Williams in 1992, 1993, 1994, 1996 and 1997, and with Benetton in 1995. Nigel Mansell, Alain Prost, Michael Schumacher, Damon Hill and Jacques Villeneuve each won a Driver's championship in the 1990s with Renault engines.

While pneumatic valve springs have become standard in Formula 1 engines, Renault has been researching computer controlled electro hydraulic valves using no camshaft, to reduce moving parts while improving valve control.

Pneumatic valve springs are also found in several Moto GP motorcycle engines, debuting in 2002 with the Aprilia RS3 Cube. In 2005, Team Roberts was the first to use pneumatic valves full time in their uncompetitive KTM powered bike. Today, almost all of the MotoGP teams use pneumatic valve technology on their bikes, including Yamaha, Kawasaki, and Suzuki. Honda only has one bike out of four that use pneumatic valves. Ducati uses a desmodromic design.

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ee also

*4-stroke cycle engine valves