Published on June 3rd, 2020 | by Subhash Nair0
Bentley Retires 6¾ L Engine – the Oldest Production V8 Ever
Bentley put together their last 6¾-litre V8 engine yesterday, officially putting to rest the longest serving motor of its kind. The iconic L-Series motor has been in service since 1959, when it was put into the Bentley S2.
Yesterday, a heavily evolved design found its way into the Mulsanne Speed. In the beginning, the motor was capable of just 180hp. 36,000 units later, the engine’s has been enhanced to produce 530hp while also emitting 99% fewer harmful emissions.
This was achieved by adding turbocharging, electronic control systems, fuel injection, variable valve timing and improving its overall design.
Here’s a short history of the engine from Bentley themselves:
A Brief History of the Bentley V8
The development of the first Bentley V8 engine began not long after the company moved to its current headquarters in Crewe. In the early 1950s, Jack Phillips, Senior Engine Designer, was asked to undertake a confidential study to find a replacement for the six-cylinder engine used in the Bentley Mark VI, R-Type and S1.
His brief was to build an engine that was at least 50 per cent more powerful than the six-cylinder it would eventually replace, while occupying the same space under a bonnet with no increase in weight. A ‘V’ configuration was the natural choice and it is a testament to Phillips and his team that the engine ran just 18 months after the start of the design process.
From the very beginning of production, engines were ‘run in’. They ran on a test bed for more than 500 hours at full throttle and covered hundreds of thousands of miles in real-world conditions to prove their worthiness. A department of skilled inspectors would then strip down the mechanics to ensure the highest standards were maintained.
The resulting 6.2-litre V8 engine was 30 lb lighter than the six-cylinder model. It made its debut in the Bentley S2 of 1959. The car featured air conditioning, power steering, electrically-operated ride control and press button window lifts – the most luxurious equipment for a car of that era.
The original V8 engine then had to be redesigned to fit into the new Bentley T-Series introduced in 1965. The engine design team focused on improving performance, while reducing the overall engine dimensions to fit the space available under a lowered bonnet.
Engine capacity was increased to the eponymous 6¾-litres in 1971 through an increase in stroke from 3.6 to 3.9 inches that delivered even more torque.
The arrival of the first iteration of the Bentley Mulsanne in 1980 required major changes to the V8, not least the need for stricter emission controls and improved passenger safety in the event of a front-end impact. The latter included a collapsible water pump, which effectively shortened the engine by four inches (10.1 cm).
The biggest single change to the engine was for the launch of the Mulsanne Turbo. With the fitment of a large single turbocharger, the 6¾-litre engine become the first forced-induction Bentley engine since those that powered Tim Birkin’s Blower Bentleys of the 1920s. Power and torque made a step change, and the single turbo setup was eventually replaced by a twin-turbo design along with fuel injection and full electronic control.
With the modernization of the Crewe facility from 1998 and an increase in production, the V8 engine also underwent on-going development. Cars such as the 2008 Bentley Brooklands V8 benefitted greatly and although separated by almost 50 years of development, the Brooklands’ V8 design clearly had its roots in the 1959 original, with almost 200 per cent more power and torque.
For the launch of the new Mulsanne in 2010, the V8 underwent a major overhaul, with a new crankshaft, new pistons, new connecting rods and new cylinder heads that brought variable valve timing and cylinder deactivation – the latter being a first for Bentley, but since adopted across the entire model range. Power stayed above 500 bhp, while torque figures peaked at 1,100 Nm – for a time, the L-series V8 made more torque than any other automotive engine in the world. At the same time, the re-engineered V8 delivered a 15% improvement in fuel economy in emissions.
The engine now reaches the end of its development and production run, but will live in for decades to come in the beloved cars of Bentley’s customers.