Drive systems and chassis | Engine technology · 42
41 · Drive systems and chassis | Engine technology
Compression with precision.
Essential for getting right to the point.
Direct fuel injection (DFI).
DFI injects fuel directly into the combus -
tion chamber at up to 120 bar with milli -
second precision using electromagnetic
injectors. The injector position and spray
geometry have been carefully designed
to improve output, torque, fuel economy
and emissions. The swirling of the fuel as
it enters each chamber increases the
mixing of air and fuel, thereby enhancing
combustion. By forming the air/fuel mix -
ture directly in the combustion chamber,
DFI contributes to engine cooling. As a
result, it was possible to increase the
compression ratio and therefore power
and efficiency.
Direct fuel injection on the diesel
engine (common-rail injection system).
On the Cayenne Diesel, direct fuel injec -
tion comes courtesy of a common-rail
injection system. The injection pressure
is now up to 2,000 bar, ensuring optimum
distribution of the air/fuel mixture – for
greater performance. The piezoelectric
injectors provide flexible injection rate
adjustment, using exactly metered
quantities of fuel, with multiple injections
for each power stroke to deliver smooth
combustion.
Cooling systems.
A high-performance engine can only
maintain its maximum capability over
a long service life if all components are
operating consistently within a specific
temperature range. The engines in the
Cayenne models are therefore designed
for efficient cooling.
In order to reduce the frictional losses
that occur during warm-up, all Cayenne
models feature comprehensive thermal
management. Using intelligent control,
it activates the different cooling circuits
individually and on demand, thereby
ensuring that the optimum operating
temperature for the engine and trans -
mission is reached more quickly. This
minimises friction – and keeps fuel
consumption and CO
2 emissions low.
The V8 engines have an enhanced coolant
management system offering effective
temperature control throughout the engine.
While 20 % of coolant flows longitudinally
through the crankcase, the remaining 80 %
serves the cylinder heads using the proven
cross-flow principle (from hot to cold).
On all Cayenne models, the piston heads
are cooled using oil-spray jets integrated
within the main lubrication system.
The entire cooling system is designed for
prolonged heav y-dut y use, e.g. off-road
driving or heav y towing and carrying
applications.
Lubrication.
The V8 engines use dry-sump lubrication
to ensure a consistent supply of oil in
all load conditions, especially in off-road
terrain. The oil reservoir is located inside
the engine. This saves on space and
reduces weight.
Oil is circulated around the V8 engines
using a demand-driven pump. This has
been designed for the toughest driving
scenarios on and off road, including per -
formance driving and extreme gradients.
The V6 engines have a wet-sump lubrica -
tion system. Ensuring a reliable supply of
oil, whatever the driving conditions.
For fuel consumption, CO
2 emissions and efficiency class data, please refer to pages 150/151.
