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==Variation of redline== The acceleration, or rate of change in piston velocity, is the limiting factor. The piston acceleration is directly proportional to the magnitude of the G-forces experienced by the piston-connecting rod assembly. As long as the G-forces acting on the piston-connecting rod assembly multiplied by their own mass is less than the compressive and tensile strengths of the materials they are constructed from and as long as it does not exceed the bearing load limits, the engine can safely turn without succumbing to physical or structural failure. Redlines vary anywhere from a few hundred [[revolutions per minute]] (rpm) (in very large engines such as those in trains and generators) to more than 10,000 rpm (in smaller, usually high-performance engines such as motorcycles, some sports cars, and pistonless rotary engines). [[Diesel engine]]s normally have lower redlines than comparably sized [[gasoline engine]]s, largely because of fuel-atomization limitations; even a small diesel engine, such as a [[Yanmar 2GM20]] found on a sailboat, has a redline of 3400 RPM continuous, with a maximum 1-hour rating of 3600 RPM.<ref name="Yanmar technical reference sheet">Yanmar technical reference sheet</ref> Gasoline automobile engines typically will have a redline at between 6000 and 7000 rpm. The [[Gordon Murray Automotive T.50]] has the highest redline of a [[Piston engine|piston-engine]] road car rated at 12,100 rpm. The [[Mazda Wankel engine#13B-MSP Renesis|Renesis]] in the [[Mazda RX-8]] has the highest redline of a production [[Wankel engine|wankel rotary-engine]] road car rated at 9000 rpm. In contrast, some older [[Overhead valve|OHV]] (pushrod) engines had redlines as low as 4800 rpm, mostly due to the engines being designed and built for low-end power and economy during the late 1960s all the way to the early 1990s. One main reason OHV engines have lower redlines is valve float. At high speeds, the valve spring simply cannot keep the tappet or roller on the camshaft. After the valve opens, the valve spring does not have enough force to push the mass of the rocker arm, pushrod, and lifter down on the cam before the next combustion cycle. [[Flathead engine]]s can have even lower redlines; for example, the [[Universal Atomic 4]], commonly used as auxiliary power on [[sailboat]]s from the 1950s to the 1980s, has a redline of just 3500 RPM. Overhead cam engines eliminate many of the components and moving mass, used on OHV engines. Lower redlines, however, do not necessarily mean lower performance. Motorcycle engines can have even higher redlines because of their comparatively lower [[reciprocating mass]]. For example, the 1986β1996 Honda CBR250RR has a redline of about 19,000 rpm. Higher yet have been the redlines of some [[Formula One]] cars, with engine speeds reaching over 20,000 rpm on the [[Cosworth TJ / CA engine|Cosworth]] and [[Renault RS engine|Renault]] 2.4-liter V8 engines during the [[2006 Formula One season|2006 season]].<ref>{{Cite web|title=Cosworth story|url=http://www.formula1-dictionary.net/engine_cosworth_story.html|access-date=2022-03-09|website=www.formula1-dictionary.net}}</ref><ref>{{Cite web|title=King of Speed: Cosworth's CA 2.4l V8|url=https://www.f1technical.net/features/18858|access-date=2022-03-09|website=www.f1technical.net|date=15 October 2013 |language=en-gb}}</ref><ref>{{Cite web|last=Engineering|first=Racecar|date=2008-09-12|title=Inside an F1 Engine|url=https://www.racecar-engineering.com/articles/f1/inside-an-f1-engine/|access-date=2022-03-09|website=Racecar Engineering|language=en-US}}</ref>
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