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.
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 542 bhp 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.
Source: Bentley Motors