Efficient Gas Flow
• The combustion chambers are of the pent-roof type, with four large area valves
per cylinder, set at a relative angle of 58 degrees. The valve diameters are 32 mm for the
inlet valves on six-cylinder engines and 31 mm on five cylinder engines and 27 for the
exhaust valves. The spark plug is located in the center. • The choice of pent-roof combustion chambers permits the use of large-diameter
valves and the shape of the chamber helps to create a tumbling motion in the mixture
during the intake stroke, thereby making the combustion process more efficient. The
tumbling motion helps to create good fuel economy, high part-load stability, high specific
performance, and low exhaust emissions. • The strength and velocity of the tumbling motion have been carefully determined
by the engineers in single-cylinder test rigs using PTV (Particle Tracking Velocimetry),
in order to optimize the combination of properties. • The camshaft bearing housing, which is also made of chill-cast aluminum, has
integrated upper bearing halves and forms the top part of the cylinder head. The lower
bearing halves are integrated in the cylinder head. CVVT- Continuously Variable Valve Timing
• The double overhead camshafts feature CVVT- Continuously Variable Valve Timing-
in order to optimize combustion and improve emission levels. This means that both the
cylinder head and the camshaft bearing housing have been redesigned for CVVT. The CVVT System Is Used In Two Different Ways
• On the normally-aspirated engine versions, it works on the inlet cam in
order to improve low-end torque and driving characteristics. • On the Volvo S80 T-6 version, it operates on the exhaust cam in order to cut
emission levels still further, especially during cold starts. • CVVT is based on the principle, using the engine's oil flow, that the engine
changes the position of the camshafts in relation to the valves by means of a hydraulic
control valve. • The opening and closing of the valves is adjusted depending on the situation
(engine load, engine speed and so on). No matter whether it is intended to control the
inlet valve timing or discharge the exhaust gases at exactly the right moment in the
combustion process in order to reduce the HC content, CVVT improves the overall
characteristics of the engine by improving driving characteristics and reducing emissions. • While we are on the subject of emissions, the emission control system in the
Volvo S80 T6 features twin catalytic converters, one for each set of three cylinders. Each
of these catalytic converters has twin oxygen (Lambda) sensors. • One of them is located in front of the catalytic converter to provide
information about the oxygen content of the exhaust gases. The other is positioned behind
the catalytic converter, thereby making it possible to control the emissions with greater
precision. • The cams are driven by toothed belt for a long and trouble-free service life
with accurate and quiet operation. They have plastic covers with rubber cushioning between
them to counteract noise emissions and prevent the covers from rattling. Computer Controlled Electronic Throttle
• The engine management system is Volvo-specific, software based and is part
of the multiplex system (described later on). Apart from being very sophisticated with a
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