TVR Speed Six engine

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The TVR Speed Six (also known as the AJP-6) was the name of a normally aspirated straight-6 engine manufactured by TVR by its TVR Power subsidiary in Coventry, England and used in several of their cars including the TVR Tuscan, TVR Cerbera, TVR Tamora and TVR Sagaris.

The engine's prototype was designed largely by independent engineer Al Melling (the "A" in AJP) originally as a 4.0 liter unit. The key design features were light weight, extremely fast throttle response and high peak horsepower

The initial 4.0 liter version of the engine as used in the Cerbera produced 350 bhp but later incarnations of the mill have reached outputs of 400 bhp and higher in cars like the Tuscan S and Sagaris.

The engine was produced in three different displacements: 3.6, 4.0 and 4.2 liters. The three versions use the same piston size but different stroke lengths depending on the power needed for the application.

All versions of the engines produced used a dual overhead cam design for the cylinder heads and advanced throttle design for improved response. In addition, the engine uses a dry sump lubrication system to reduce engine size and increase power.

There have been complaints of reliability and durability issues from some users. In some cases these were attributed to faulty components provided by TVR's parts suppliers and still other cases were attributed to user abuse. Extremely sensitive to being pushed 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 developed it into the limited-production V12 Speed Twelve racing engine.