Volvo’s Twin Scroll turbocharger makes S80 3.0T engine a smooth operator

  • 3.0T engine adds extra dimension to the S80 engine range
  • Maximum torque on tap from just 1 500 rpm
  • Twin scroll turbocharger technology delivers power smoothly

Volvo’s signature Scandinavian luxury sedan, the Volvo S80, now receives a smooth power injection in the shape of the technologically advanced six-cylinder, 210 kW 3.0T performance engine which delivers its power through the All-Wheel Drive system in this flagship model.

“The 3.0T engine adds an extra dimension to the S80 engine range,” says Hans Wikman, vice president for vehicle line large cars at the Volvo Car Corporation. “The engine has been programmed to provide the highest possible performance with the lowest possible fuel consumption and exhaust emissions.”

The 3.0T petrol engine, which was a finalist for the annual Ward’s 10 Best Engine awards, is based on the compact 3.2-litre in-line aluminium engine that has been part of the S80 engine range since the introduction in March 2006. The turbo version of the normally aspirated 3.2-litre has a displacement of 3.0 litres, producing 210 kW and no less than 400 Nm of torque.

Maximum torque is on tap from just 1 500 rpm and remains available all the way up the rev range, resulting in remarkably quick acceleration (0-100 km/h in 7.2 seconds) and smooth driveability.

The somewhat smaller cylinder displacement of the turbo version, owing to the slightly narrower cylinder bore and shorter stroke, is compensated by the turbocharger which in this engine takes in exhaust gases in two stages, with the inflow divided into two lots of three cylinders each, a system known as twin-scroll technology.

The twin-scroll technology is a main feature of this powerful and efficient engine, and the result is an impressige torque curve which actually represents a flat line on 400 Nm from where it starts at very low engine revolutions of only 1 500 rpm. It permits the use of a more compact and uncomplicated turbocharger and provides extremely swift response, fully on a par with that from twin turbochargers.

The technical solution to create a compact 6-cylinder engine that could be mounted transversely, was retained in the turbocharged 3.0T – with gear housing also located at the rear of the engine and all auxiliaries located above the gearbox. The oil sump is the same while the intermediate section, cylinder block, cylinder head and oil separation have been redeveloped to suit turbo operation.

The main difference between the engines is the turbocharger that uses twin scroll technology. Other changes between the normally aspirated and turbocharged 6-cylincer have been done to the:

  • Oil separator housing, cylinder head, cylinder block, intermediate section;
  • Camshafts;
  • Valves, tappets;
  • Manifolds;
  • Inlet manifold, ETM (Electronic Throttle Module);
  • Crankshaft, connecting rods, pistons;
  • Crankcase ventilation;
  • Lubrication system; and
  • Catalytic converter, oxygen sensors.

The cylinder head of the 3.0T has been adapted for turbo operation with a new combustion chamber and new inlet and outlet ports. The cylinder block has a smaller bore than the 3.2-litre and it has been machined for oil delivery to the turbocharger. To effect oil return from the turbocharger the intermediate section has also been re-machined.

The camshafts in the 3.0T have a hollow construction which results in low weight and the intake camshaft is equipped with CVVT (Continuous Variable Valve Timing). Both inlet and outlet valves of the 3.0T have a smaller diameter than the non-turbo 6-cylinder. The smaller diameter for the outlet valves contributes to increased gas speed and accordingly increased speed for the exhaust turbine of the turbocharger.

To withstand the higher exhaust temperatures that turbo operation produces, the outlet valves have been manufactured in a temperature resistant material that contains 70% nickel. Both inlet and outlet valves are controlled via fixed tappets.

The crankshaft for the 3.0T has a slightly shorter stroke than that of the normally aspirated 6-cylinder and the connecting rods, with the same measurements for both engines, have been reinforced in the upper section for improved resistance to the higher load exerted on them in a turbocharged engine.

The exhaust manifold is produced in high-alloy cast steel to withstand the high loading and temperature of the turbocharged combustion process. In the event of extremely high loading the manifold could reach a temperature of 900ºC.

Twin Scroll turbocharger techology
Twin Scroll technology means that the outlet or exhaust manifold consists of two separate ducts that run into the turbine section of the turbocharger. Exhaust gases are evacuated from the cylinders in accordance with the ignition sequence, i.e. when cylinder 1 is evacuated of exhaust gases it is followed by cylinder 5, then cylinder 3-6-2-4.

Consequently the turbine rotor is fed alternately by exhaust gases from the two different ducts in the manifold and the turbine housing.

The Twin Scroll technology has been selected so that it produces equally high output but requires less space than an equivalent system with two separate turbochargers. By means of the gases that flow from the separate exhaust ports not affecting each other in a negative way, the pulse energy from the exhaust gases is utilised very efficiently, and a high torque is achieved at low engine revolutions.
Full torque, 400Nm, is achieved at 1500 rpm.

This results in very good performance when starting from stationary and good acceleration characteristics.

The turbocharger is cooled both by the engine’s cooling system and by the engine oil. The engine oil also contributes with its lubrication.

Cooling the turbocharger
During operation the turbocharger, which contains bearings that run at very high rotation, is cooled by the circulating engine oil. At the same time there is a weak throughflow of coolant. In the very important cooling phase after the engine and its systems have been switched off, the turbocharger is cooled by self-circulating coolant.

In this position the coolant in the turbocharger could reach a temperature of 125ºC. The coolant then starts to boil, and the gas bubbles that form rise to the expansion tank. The rising gas bubbles are replaced in the turbocharger by colder coolant. This self-circulating process is known as thermosyphon and could continue for 5 to 10 minutes.

Double cooling fans are used for the 3.0T engine in hot markets such as South Africa in order to achieve maximum possible cooling capacity.

All Wheel Drive with Instant Traction
The 3.0T model in the Volvo S80 is equipped with Volvo’s All Wheel Drive. Using an electronically controlled hydraulic clutch, the AWD system distributes drive between the front and rear wheels to ensure the best possible road grip in all situations.

The 3.0T engine is optimised for a very sporty driving experience. At the same time, it is programmed to give the highest possible performance with the lowest possible fuel consumption and exhaust emission levels. With four-wheel drive – All-Wheel Drive – the engine is utilised in an optimal manner by transferring the maximum amount of power very effectively onto the road surface.

The system features Instant Traction, which shifts drive at lightning speed from the front to the rear wheels when starting on a slippery or loose surface.