<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2007) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2007) (Learn how and when to remove this template message) </Td> </Tr> <P> Engine tuning is an adjustment, modification of the internal combustion engine, or modification to its control unit, otherwise known as its ECU (Engine Control Unit). It is adjusted to yield optimal performance, to increase an engine's power output, economy, or durability . These goals may be mutually exclusive, and an engine may be detuned with respect to output (work) in exchange for better economy or longer engine life due to lessened stress on engine components . </P> <P> It has a long history, almost as long as the development of the automobile in general, originating with the development of early racing cars, and later, with the post-war hot - rod movement . Tuning can describe a wide variety of adjustments and modifications, from the routine adjustment of the carburetor and ignition system to significant engine overhauls . At the other end of the scale, performance tuning of an engine can involve revisiting some of the design decisions taken at quite an early stage in the development of the engine . </P>

What does it mean to tune an engine