according to Volvo (a press release found at AutoWorld.com):

"VOLVO'S NEW FAMILY OF "SLIM" ENGINES POWER ALL NEW VOLVO PASSENGER CARS

To ensure build quality and to maximize manufacturing efficiencies, Volvo builds both of the S80's six-cylinder engines-indeed all of its engines in a modular fashion. Volvo calls this new family of engines SLIM, for Strong, Light, In-Line and Multi-valve. SLIM engines power all new Volvo passenger cars worldwide.

A large number of components are new compared to previous version of this engine while visually these engines are almost identical about 90% of the main components are new. Both S80 engines consist of several main parts, each made of cast aluminum. At the bottom is the oil sump made of high-pressure die-cast aluminum, with an integrated oil cooler. The lower crankcase and the cylinder block are also of high-pressure, die-cast aluminum and feature reinforcing ribs to add structure for rigidity and reduce noise and vibration. The cylinder head is made of chill-cast aluminum. The gray-iron cylinder liners are cast in place during the casting of the block. All oil and coolant passages are cast in place during production eliminating the need for extra machining. The crankshafts are made of forged vanadium steel and ride with seven main bearings.

While both engines share a 90-mm stroke and bore centers, the naturally aspirated version has a slightly larger cylinder bore. The 2.9-liter naturally aspirated engine has a bore of 83 mm, while the 2.8-liter twin turbo has a bore of 81 mm.

Both cylinder heads have pentroof combustion chambers, centrally placed spark plugs and four valves per cylinder. The valves are set a relative angle of 58 degrees. The pentroof design allows the use of

relatively large valves for optimum breathing. Intake valves have 32 mm diameter faces for the 2.9L engine and 31 mm for T6; exhaust valves are 27 mm in diameter.

The camshaft bearing housing carries the camshafts upper bearings and is, like the cylinder head, made of chill-cast aluminum and, in fact, forms the top of the cylinder head. The lower bearings for the camshaft are integrated into the cylinder head.

Both engines also share a new generation of electronic controls Bosch, ME 7.0, which is a development of Motronic 4.4 used previously. ME 7.0 features a communication network between the electronic control module and the assorted sensors and controllers. Thanks to the new electronic control system, all S80 models feature electronic throttle (drive by wire) control, dual catalysts with two Lambda sensors each and Continuously Variable Valve Timing. However, though the CVVT's purpose is to optimize combustion efficiency, its mission on the naturally aspirated and turbocharged engines are different and so the systems operate differently.

To improve low-end torque for improved driving response at lower speeds as well as idle quality on the naturally aspirated engine, the CVVT is mounted on the intake camshaft. However, the CVVT on the turbocharged engine is used for improving cold-start exhaust emissions and so the system operates on that engine's exhaust camshaft. The naturally aspirated engine's intake camshaft operates over a 20 degree range (40 degrees of crankshaft rotation) from stop to stop. And over a 1500-rpm range, between 1500 and 3000 rpm, the system increases engine torque by 10 percent. The turbocharged engine's exhaust camshaft operates over a range of 15 degrees of camshaft rotation (30 degrees of crankshaft rotation) and helps lower the amount of hydrocarbons (HQ) in the exhaust.

While the two valve-timing control units differ slightly in size and appearance, they both operate by responding to a computer controlled flow of pressurized oil. The valve regulating that oil pressure is under the purview of the engine's ECK Electronic Control Module. Also under the control of the ECM is the engine's throttle. There is no mechanical link between the accelerator pedal and the throttle. Besides offering improved throttle response to driver input, the electronic throttle also provides more precise and smoother idle and reliable cruise control speed.

Both six-cylinder engines are equipped with dual catalytic converters for optimum regulation of harmful exhaust emissions. Each catalyst has two oxygen (Lambda) sensors. One is mounted between the engine and the catalyst, the other aft of the catalyst. By constantly comparing the content of the exhaust gases the ECM is able to ensure a more precise fuel-air mixture, narrowing its findings to only three cylinders thanks to the split exhaust system.

TWIN-TURBOCHARGED ENGINE

The 2.8-liter twin-turbocharged engine used in the S80 T6 has two small turbochargers rather than one larger one. Each turbo feeds three cylinders and is fed by the exhaust of three cylinders, a benefit of the engine's true dual-exhaust system. Two smaller turbos respond far more quickly than one larger one due to the reduced mass of the smaller turbines and impellers and the inherent reduced inertia. The twin turbos feed the engine through intercooler for increased performance. Boost of the two turbos is regulated independently by the ME 7.0 control unit. Maximum boost is limited to 10.5psi.

Given the electronic control of the engine, the 2.8-liter twin-turbo engine in the T6 has a solid 8.7:1 compression ratio which means that base, non-turbo enhanced performance is still sprightly. The naturally aspirated 2.9-liter S80 engine has a somewhat higher 10.7:1 compression ratio. Both engines deliver peak performance when running on premium, 91 RON fuel EPA fuel consumption is 19mpg city, and 27mpg highway with combined total of 27mpg for the S80 2.9. The S80 T6 is 18mpg city, and 27mpg highway with combined total of 27mpg."

Scott

'98 V70