• Improved performance with lower emissions
• 13 percent gain in power, 17.5 percent gain in torque
• Larger, electronically controlled turbocharger
• Improved fuel injection system
• More powerful engine management system
• More efficient EGR system
• Maintenance-free particulate filter
• Six-speed gearboxes (manual and automatic)
• All-wheel drive with Instant Traction for all larger Volvo models
• Volvo Car Australia yet to confirm availability

A better performing, more refined new-generation turbocharged diesel engine powers Volvo Cars large-car model range for 2006. Volvo will offer the new 2.5-litre five-cylinder engine in its S60, V70, XC70 and XC90.

Amongst impressive gains in NVH refinement, the new engine's headline features are a sharp reduction in tailpipe emissions, a 16kW increase in peak power and a substantial 60Nm improvement in peak torque.

Rated at 136kW and 400Nm, Volvo's new diesel engine is characterised by rapid throttle response at low and high rpm. “We have improved nearly everything in the engine,” says Jörgen Svensson, chief programme engineer. “The driver will perceive it as a lively petrol engine, only more powerful and more environmentally efficient.”

Delivering improved power and torque across a wider rev range, the D5 diesel five-cylinder engine provides excellent high-speed performance with fast acceleration and efficient pulling power, even when driving up long, steep hills, with no need to change down.

This more muscular diesel engine will be available in Europe and other selected markets; however, hot climate markets such as Australia are yet to confirm availability.

Advanced water-cooled turbocharger
Much of the performance increase can be attributed to an upgraded intake and exhaust gas exchange system, a new turbocharger, and an improved injection system.

Most of the air and exhaust channels have been given increased volume and more gentle bends for more efficient gas flow.

The new-generation turbocharger has electronic control, resulting in fast and precise management of the charge pressure. A larger compressor wheel provides higher torque and output. Furthermore, the variable vanes have been cambered for more efficient gas flow at all settings, resulting in increased turbo efficiency. The improvements result in faster acceleration and better overall performance at higher engine speeds.

The turbocharger's centre housing is now water-cooled, which is unusual in diesel engines. Water cooling was required because of the engine's much higher outputs, and because water cooling continues to provide temperature control of the turbocharger's centre housing well after the engine has been switched off. This is particularly beneficial during short stops after high-speed driving, such as when refuelling.

Refined injection technology
The use of a new electronically controlled multi-throttle system in the inlet ports allows for infinitely variable regulation of the swirl level, and combustion can be adjusted extremely accurately according to the driving situation and engine speed and load.

“We have also made the combustion chambers larger, thereby lowering compression,” says Svensson. "By doing so, we have gained two things: higher performance and lower emissions.”

The injection system employs new injectors with seven finer nozzle openings as opposed to five in the previous engine's injectors. This results in better, finer atomisation of the fuel mixture and more efficient combustion.

Fuel injection takes place in three phases: pre-injection, primary injection and post-injection. The last step is new and contributes to cleaner combustion and to regeneration of the particulate filter.

A completely new, electronically regulated quick glow system results in considerably reduced glow times, also making it easier to start the engine in cold weather.

New management system contributes to reduced emissions
The new diesel engine has very low emissions, thanks to a number of new and refined functions. For example, emissions of nitrogen oxides (NOx) have been halved. A new-generation engine management system, with increased capacity and a greater number of sensors, offers more accurate control of the engine’s functions. This includes electronic control of the throttle and the new, more powerful EGR (Exhaust Gas Recirculation) valve for more precise regulation of the air supply and recirculation of exhaust gases.

“We also have a completely new EGR cooler,” says Svensson. “This lowers the combustion temperature very efficiently, thereby reducing emissions.”

The catalytic converter is positioned nearer to the engine, not just on manual but also on automatic versions, to promote faster warming and thus faster start-up of the exhaust cleaning process. The catalytic converter is also larger than before. In addition it has been supplemented with an oxygen sensor that precisely regulates the fuel mixture and emissions.

Particulate filter is standard
All versions of the new diesel engine have a particulate filter as standard equipment. It very effectively removes soot particulates from the exhaust gases, with filtration efficiency above 95 percent.

The filter is a CDPF – Coated Diesel Particulate Filter – in which a special coating helps burn the particulates. Therefore, no additives are needed, and the filter requires no maintenance. Burning away soot particulates takes approximately 20 minutes and occurs automatically at 500 to 1000km intervals, depending on driving conditions.

In addition to the technical changes, the diesel engines’ service interval has been extended from 20,000km to 30,000km.

Six-speed manual and automatic gearboxes
As standard equipment, the D5 engine is combined with a six-speed manual gearbox to accommodate its very high torque. The six speeds contribute to sportier driving.

Furthermore, a new automatic gearbox will be introduced during the course of the year. It also has six speeds and is available as an option. The new automatic transmission contributes to very fast response, particularly when the kick-down function is used. It also has a lock-up feature that is allowed to slip over a wide range of engine speeds for effective pulling power and good drivability, particularly when transporting heavy loads or towing.

All-wheel drive with Instant Traction
The improved AWD system with Instant Traction, which was introduced on the Volvo XC90 V8, can now be combined with other XC90 engines. The system will also become available for all-wheel drive XC70s. Instant Traction makes starting easier on slippery surfaces by immediately distributing the right amount of power to the rear wheels the instant the car starts to move.

“The D5 engine with a six-speed gearbox and all-wheel drive is a nearly unbeatable combination,” claims Svensson. “It offers enormous driving pleasure while also providing power and low-rpm response for the most demanding uses.”

Summary
Most of the measures taken on the new 2.5-litre diesel engine result in increased performance and reduced emissions. The primary purposes are explained in the following summary:

For increased performance

• Injection system has been improved with new injectors and a more advanced injection process
• New-generation turbocharger with larger compressor wheel, cambered vanes and electronic control
• Gas exchange system has been upgraded for optimum air flow and exhaust gas flow

For lower emissions

• New-generation engine management system with a greater number of sensors for more precise regulation
• New EGR (Exhaust Gas Recirculation) system with faster regulation of the flow Improved EGR cooling
• New air throttle is electronically controlled to more effectively control EGR flow, reduce noise and regulate the temperature
• Air swirl in the combustion chamber is infinitely variable for more efficient combustion
• Lowered compression ratio (from 18:1 to 17:1). Larger combustion chambers lowers compression temperatures and reduces emissions
• New quick glow system electronically controlled for faster cold starts
• Larger catalytic converter fitted with an oxygen sensor for precise emission control
• Coated Diesel Particulate Filter (CDPF) is standard