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TVR Speed Six engine

TVR Speed Six engine

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The TVR Speed Six was the name of a normally aspirated straight-6
Straight-6
The straight-six engine or inline-six engine is a six-cylinder internal combustion engine with all six cylinders mounted in a straight line along the crankcase...

 engine manufactured by TVR
TVR
thumb|right|240px|TVR No.2, the oldest surviving TVR, located at [[Lakeland Motor Museum, Newby Bridge, Cumbria]]TVR was an independent British manufacturer of sports cars. Until 2006 it was based in the English seaside town of Blackpool, Lancashire, but has since split up into several smaller...

, and used in several of their cars including the TVR Tuscan, TVR Cerbera
TVR Cerbera
The TVR Cerbera is a sports car manufactured by TVR between 1996 and 2003. The name is derived from Cerberus the three-headed beast of Greek legend that guarded the entrance of Hades....

, TVR Tamora
TVR Tamora
The TVR Tamora is a 2-seater sports car built from 2002 by British firm TVR, filling the gap left by the company's Chimaera and Griffith models...

, TVR T350
TVR T350
The TVR T350 is a sports car manufactured by TVR from 2002 to 2006. It is based on the TVR Tamora, and is powered by TVR's Speed Six engine in 3.6 litre form, producing . The T350 was available in coupe and targa versions, the coupe version being known as the T350C, and the targa version the T350T...

 and TVR Sagaris
TVR Sagaris
The TVR Sagaris is a sports car designed and built by the British manufacturer TVR in their factory in Lancashire.The Sagaris made its debut at the MPH03 Auto Show in 2003. The pre-production model was then shown at the 2004 Birmingham Motorshow. In 2005 the production model was released for public...

.

The engine's prototypes (sometimes referred to as AJP-6) were designed and delivered by independent engineer Al Melling
Al Melling
Al Melling is an automobile engineer.- Fashion Design :At the beginning of the eighties he became involved in the fashion industry. He owned a company in London throughout the eighties which designed ladies’ fashion garments. As owner he became interested in the whole lifecycle of garment...

 (the "A" in AJP) as both 3.6 and 4.0 litre units. It is reputed that many of its key design elements (particularly the valvetrain) were first seen in the 1991 Suzuki GSX-R750M motorcycle engine, which was also a Melling designed unit.

The key design features were an all alloy block and head, dry sump
Dry sump
A dry sump is a lubricating motor oil management method for four-stroke and large two-stroke piston internal combustion engines that uses external pumps and a secondary external reservoir for oil, as compared to a conventional wet sump system....

 lubrication system and throttle body electronic fuel injection system. This gave lightweight, extremely fast throttle response
Throttle response
Throttle response or vehicle responsiveness is a measure of how quickly a vehicle's prime mover, such as an internal combustion engine, can increase its power output in response to a driver's request for acceleration, such as a pedal being pressed...

 and high peak horsepower
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...

.

The engines that actually went into production however were TVR modified versions of the original AJP-6 prototypes. Prominent modifications were a switch from a billet steel crank to cast iron and to remove an oilway from the exhaust side of the cylinder head (the original Melling engine design had an oilway on both the inlet and exhaust sides). It was suggested that this caused poor lubrication and cooling to the head around cylinder 6 leading to premature valvegear failures, detonation and a reputation for poor reliability. Subsequent development work has shown that the primary cause was actually mismatched surface hardnesses between the cam lobes and the finger followers resulting in accelerated wear rates to the finger followers. Later versions of the engine and aftermarket components have since eliminated these problems.

It is not clear exactly why these modifications were done, however amongst rumors of a soured business relationship between Melling and TVR, it is believed that the primary reason was to reduce the unit production costs.

The initial 4.0 litre version of the engine as used in the Cerbera produced 350 bhp but later incarnations of the engine have reached claimed outputs of up to 405 bhp in cars like the Tuscan S and Sagaris.

The engine was produced in two different displacements: 3.6, and 4.0. The two versions use the same piston size but different stroke lengths depending on the power needed for the application.

The heads on all versions of the engines are twin-cam 24-valve, with finger follower valve actuation. There is one throttle and injector per cylinder (throttle body EFI), as well as equal length tubular exhaust manifolds. In addition, the engine is canted 30 degrees to the left and the dry sump
Dry sump
A dry sump is a lubricating motor oil management method for four-stroke and large two-stroke piston internal combustion engines that uses external pumps and a secondary external reservoir for oil, as compared to a conventional wet sump system....

 lubrication system enables the engine to be mounted lower in the vehicle chassis.

There have been complaints of durability issues from some users. In some cases these were attributed to faulty components (particularly the finger followers) provided by TVR's parts suppliers and other cases were attributed to user abuse. The engine is claimed to be extremely sensitive to being revved hard without being allowed to warm up fully first. Also, its dry sump oil system can make it difficult for new owners to accurately judge the level of oil in the reservoir and any engine run without adequate lubrication can be subject to mechanical damage.

TVR specialists TVR Power now offer core exchange engineshttp://www.tvrpower.co.uk/upgrades/ taken out to 4.3 and 4.5 litres, giving more power.

TVR developed the Speed Six into the limited-production V12
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....

 Speed Twelve
TVR Speed Twelve engine
The TVR Speed Twelve engine is the name of a V12 engine manufactured by TVR for use in the TVR Speed 12 race car, and later the TVR Cerbera Speed Twelve road car in which on the Cerbera Speed 12 went into production....

racing engine.