TVR Speed Six engine
| TVR Speed Six engine | |
|---|---|
| Overview | |
| Manufacturer | TVR |
| Production | 1999 – 2007 |
| Combustion chamber | |
| Configuration | Straight-6 |
The TVR Speed Six was the name of a naturally aspirated straight-6 engine manufactured by TVR, and used in several of their cars including the Tuscan, Cerbera, Tamora, T350, Sagaris, and Typhon. It is the most powerful naturally aspirated straight-6 engine ever to be fitted to a production car.
The engine's prototypes (referred to as AJP-6) were designed and delivered by independent engineer Al Melling (the "A" in AJP) as both 3.0 and 3.5 litre units. Many of its key design elements (particularly the valvetrain) were first seen in the 1991 Suzuki GSX-R750M motorcycle engine (also a Melling design).
The key design features were an all alloy block and head with twin-camshafts, finger follower 24-valve actuation, one throttle and injector per cylinder (throttle body EFI), equal length tubular exhaust manifolds dual 3-way catalytic converters and a dry sump lubrication system allowing the engine to be mounted lower in the vehicle chassis. These features enabled the engine to provide lightweight, compact dimensions, extremely fast throttle response and high peak horsepower.
In order to reduce unit production costs, the engines that actually went into production, called Speed Six, were TVR modified versions of the initial AJP-6 prototypes with 3.6 and 4.0 litre capacities. Prominent modifications were alterations to valve train geometry, a switch from a billet steel crank to cast iron (with a crank damper), different con-rods, oil filter relocation to the inlet side of the engine, and removal of the exhaust cam oil feed. The two different capacities were achieved through stroke alterations from a con-rod design able to accommodate two different stroke lengths, and different piston crown designs altering the compression ratios. The bores diameters were shared.Pistons were made in Italy by Asso Werke from pre-existing casts, initially designed for the Rotax-Aprilia RSV 1000 engine. Those casts, refused by Rotax, were modified and used to produce the smaller Speed Six pistons.
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