The driving force behind the Flying Spur V8: Engine facts and figures
January 15, 2021 by Bentley
• 4.0-litre, twin-turbocharged V8 develops 135+ bhp per litre
•Twin-scroll turbochargers mounted centrally in the V provide rapid response and maximum torque of 770 Nm, available from 2000 rpm
•Turbines operate at a peak temperature of 950°C – as hot as lava
•Proximity of catalytic convertors to turbos reduces cold start emissions
•Centrally mounted fuel injectors in combustion chambers work at a pressure of 250 bar
•Lightweight alloy pistons move at up to 20 metres per second
•Iron alloy bore coating just 150 microns thick reduces cylinder wear to negligible level
•Cylinder deactivation in 20 milliseconds - one tenth of a blink of an eye
•Camshafts adjust valve timing by up to 50 degrees and can deactivate half of the cylinders
•Grand touring range of more than 441 miles, CO2 emissions of 288g/km, and yet 0-60 mph in 4.0 seconds (0-100 km/h in 4.1 seconds)
The new Flying Spur V8 builds on Bentley's more than 60-year tradition of using cross-plane V8 engines. The V8-powered Flying Spur offers a characterful engine note, greater range between fuel stops and a reduction in CO2 emissions – while still offering breath-taking performance. This unlikely combination has been achieved by using the latest engineering knowledge and technology.
The Bentley 4.0-litre V8 engine is a thoroughly modern engine, with a block cast from high strength aluminium and with twin-scroll turbochargers and primary catalytic convertors positioned in the V of the engine. Fuel injectors and spark plugs have been centralised within each combustion chamber to ensure optimal spray patterns and combustion paths, and the camshafts are variable by up to 50 degrees, with the ability to deactivate half of the cylinders when the engine is running at part load – turning it into a perfectly balanced V4.
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A Modern, Highly Efficient V8 Powertrain
The design concept of the V8 engine has ensured the engine delivers a high level of power and torque, whilst still achieving lower emissions and the best possible efficiency.
The compact V configuration uses a five bearing crankshaft, harnessing the power from the lightweight pistons. To minimise frictional power losses, the crankshaft also directly drives the water pump and timing chains via an intermediate shaft to improve efficiency.
An exactly square engine, matching the stroke length to the 86 mm cylinder bore, gives the best balance between power and torque, and with the help of twin-scroll turbochargers the engine develops over 135 bhp per litre – meaning a top speed for the Flying Spur V8 of 198 mph (318 km/h).
Turning Waste into Energy
The V8 produces a peak power of 550 PS (542 bhp, 404 kW), with maximum torque of 770 Nm at 2000 rpm, maintaining this as a flat plateau through to 4500 rpm.
A key feature of the twin-scroll turbochargers are the two separate, parallel flow channels in the turbine housing specifically guiding the exhaust gases to the vanes of the turbine wheel, resulting in high torque being available at low speeds. The turbochargers are located inside the V of the engine, minimising the distance the exhaust gases travel from the engine to the turbochargers which can operate at 176,000 rpm and generate up to 1.6 bar of boost pressure. The resulting instantaneous torque output delivers a 0-60 mph time of 4.0 secs (0-100 kph, 4.1 secs).
Additionally, like the central turbocharger layout, another design feature of the eight-cylinder engine is the close proximity of the catalytic converters to the cylinders inside the V. This configuration allows the emissions control system to come up to its optimal operating temperature quickly. The catalytic converter heating is accelerated in the engine start phase by opening the turbocharger wastegates.
The Perfect Mix
Two high pressure fuel pumps driven directly by the camshafts supply the eight solenoid-driven injectors with fuel at a pressure up to 250 bar – 14 times the boiler pressure required to move a 60 tonne steam locomotive.
The injectors are mounted centrally in the combustion chamber immediately adjacent to the spark plug, producing jets of fuel through seven nozzles into each cylinder to achieve the optimum spray pattern – and therefore air/fuel mixture - before ignition. The design of the air inlet ports supports increased tumble in the flow of the air charge entering the cylinder, with this turbulence helping to disperse fuel across the cylinder for a cleaner combustion process and reduced emissions.
To withstand high stress and bore wear, the cylinder bores are coated with an iron alloy using an atmopheric plasma spraying process, creating a coating that is robust yet just 150 microns thick, similar to the thickness of a sheet of paper.
Adaptable in Changing Situations
To maximise fuel economy, the V8 engine can shut down four of its eight cylinders under light-load conditions, when torque demand is below 250 Nm and engine speed is below 3500 rpm. The change is imperceptible to the occupants – with deactivation times of around 20 milliseconds (a tenth of the time it takes to blink).
The engine uses a two-stage sliding cam system which switches off cylinders two, three, five and eight as necessary via the intake and exhaust valves. The result is a fuel consumption benefit to the customer of up to 30 per cent depending on engine load and speed, which means increased range, lower environmental impact and longer driving between fuel stops.
Beyond the Driving Force
The new Flying Spur V8 has been engineered to deliver driver-focused ability, whilst offering passengers the refinement, comfort and technology expected from a grand limousine.
The Flying Spur range is purposeful yet elegant with classic Bentley design, best-in-class execution, and authentic materials. The new Flying Spur V8 not only has contemporary engine technology, but also includes the latest driver assistance and infotainment systems for enhanced safety, security and relaxation on every journey.