Volvo's New Revised Engines
GREATER DRIVING PLEASURE, QUIETER OPERATION AND LOWER FUEL CONSUMPTION
Volvo is now equipping more car models with new revised engines. They offer a number of striking benefits, including improved driving characteristics, quieter operation and fuel consumption reduced by as much as 7 %.
The new revised engine programm is currently being introduced successively in all Volvo's petrol-driven models. It is based on the N-series, which is the family name of all the engines produced at the Volvo engine plant in Skövde in Sweden. These revised engines have already been introduced in the five- and six-cylinder versions of the Volvo S80. They are now also available in the naturally-aspirated engines in the Volvo S40, Volvo V40, Volvo S70, Volvo V70 and Volvo C70 Coupe and, within the space of the next one to two years, these engines will also be introduced in most of the turbocharged models. This engine revision, which is so comprehensive that virtually all the moving parts in the engine are new, gives a Volvo with a new engine a number of striking benefits compared with the previous generation.
- Higher torque, especially in the lower half of the engine speed range, makes the car more lively and therefore more fun to drive.
- Lighter crankshaft movements and reduced friction between the
moving parts of the engine result in quieter operation.
- A number of new technical features related to the combustion process reduce fuel consumption by seven to eight per cent. In addition, emissions are reduced.
Cutting fuel consumption is one of Volvo's most important challenges: the fuel consumption of new cars sold in the EU in 2008 shall be 25% lower than in 1995. Here are the most important technical design solutions which help to give the new engines all their impressive benefits:
Variable valve timing
The CVVT (Continuously Variable Valve Timing) technique produces both higher torque at low engine speed and lower fuel consumption. The technology is based on one of the camshafts being able to turn. The intake camshaft can turn up to 20 degrees in relation to the exhaust camshaft, thereby making it possible to vary the time overlap between the intake and exhaust process. Using this system, it is possible to bring forward the time at which the intake valves close in relation to the time at which the exhaust valves open and thus produce higher torque at lower engine speeds. On the other hand, when driving on main roads when the engine is not revving at high speed, a function which technicians call maximum overlap is used; the exhaust valves do not close until the intake valves have been open for a while. This means that some of the exhaust gases are recirculated back into the cylinder at the same time as the new fuel/air mix is injected. As part of the fuel/air mix is replaced by exhaust gases, the engine is more fuel-efficient. This functions very effectively when full output is not required. The driver notices nothing while driving.
Lower mass and less internal friction
By making a number of the vital moving parts in the engine, such as the pistons, gudgeon pins and counterweights, smaller or lighter, the mass that is in motion inside the engine has been reduced by about 25 per cent. In absolute figures, this means that the engine has to pull a mass weighing 3.5 to 4.5 kilograms less, depending on the variant. As the pistons are shorter, the length of the connecting rod has been increased. This then results in a smaller plumb angle, which reduces the lateral force - and thereby the friction - when the pistons move. A number of advantages result when there is less mass in motion and less internal friction. Performance improves, while both noise levels and fuel consumption are reduced.
Improved cooling system
In the past, piston cooling was only used on turbocharged engines. It is now also being introduced on naturally-aspirated engines. In addition, all the engines have external oil coolers. Piston cooling has two principal benefits:
- It is possible to obtain higher output from the engine without
- The piston ring can be moved up a couple of millimetres. Positioning the piston ring 5 mm instead of 7 mm from the top of the piston reduces the small "pocket which forms between the piston, the piston ring and the cylinder wall. This is important from an environmental angle, as it reduces the amount of unburnt hydrocarbons which collect in this "packet".