Redline
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Redline refers to the maximum engine
The word is also used as a verb, meaning to ride or drive an automotive vehicle above the redline. The actual term redline comes from the red bars that are displayed on tachometers in cars starting at the rpm that denotes the redline for the specific engine. Operating an engine in this area is known as redlining. Straying into this area usually does not mean instant engine failure, but may increase the chances of damaging the engine.
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 rev without succumbing to physical or structural failure.
Redlines vary anywhere from a few hundred
In contrast, some older
Motorcycle engines can have even higher redlines because of their comparatively lower
Rev-limiter and implementation
Most modern cars have computer systems that prevent the engine from straying too far into the redline by cutting fuel flow through the
However, even with these electronic protection systems, a car is not prevented from redlining through inadvertent gear engagement. If a driver accidentally selects a lower gear when trying to shift up or selects a lower gear than intended while shifting down (as in a motorbike sequential manual transmission), the engine will be forced to rapidly rev-up to match the speed of the drivetrain. If this happens while the engine is at high RPMs, it may dramatically exceed the redline. For example, if the operator is driving close to redline in 3rd gear and attempts to shift to 4th gear but unintentionally puts the car in 2nd by mistake, the transmission will be spinning much faster than the engine, and when the clutch is released the engine's rpm will increase rapidly. It will lead to a rough and very noticeable engine braking, and likely engine damage. This is often known as a "money shift" because of the likelihood of engine damage and the expense of fixing the engine.
Redlining in a diesel engine can be caused by the engine receiving fuel from an unintended source, such as flammable vapour in the intake air, or a broken oil seal in a turbocharger. This is known as diesel engine runaway, and can be stopped by blocking the air intake, or opening the decompression valve.
See also
References
- ^ "Glossary of Car Terms". caranddriver.com. 15 June 2009.
- ^ Yanmar technical reference sheet
- ^ "Cosworth story". www.formula1-dictionary.net. Retrieved 2022-03-09.
- ^ "King of Speed: Cosworth's CA 2.4l V8". www.f1technical.net. Retrieved 2022-03-09.
- ^ Engineering, Racecar (2008-09-12). "Inside an F1 Engine". Racecar Engineering. Retrieved 2022-03-09.