Industry News
Volvo D5: Two Turbochargers for Optimum Performance
By source: Borg Warner
Apr 29, 2009, 21:14

Volvo is employing two-stage turbocharging from BorgWarner to further enhance driving pleasure and improve energy efficiency in its new five-cylinder diesel engine

The engineers at Volvo are relying on BorgWarner’s R2S® regulated two-stage turbocharging system for their new D5 engine, which will be used to power the luxury S80 model. During the development process, the main focus was not so much on exploiting all the potentials to maximize output but rather on fulfilling the high demands regarding driving dynamics combined with low fuel consumption. The developers met these requirements by using two series-connected turbochargers that deliver a continuously high boost pressure over the entire engine speed range. Furthermore, R2S helps to significantly reduce the fuel consumption of the 2.4-liter diesel engine — which is already certified according to the Euro 5 emissions standard — to an average of 6.2 l/100 km.

Turbocharging is a key technology in modern engine concepts for meeting ambitious targets with regard to efficiency, dynamics and sustainability. In view of the demand for high exhaust gas recirculation rates to achieve the lowest possible emissions, these targets could only be achieved by two-stage turbocharging. The Volvo engineers relied on BorgWarner’s R2S turbocharging system to ensure that the D5 diesel engine fulfilled their objectives regarding driving dynamics and fuel consumption. The sequentially arranged, differently sized turbochargers guarantee optimum engine response at all times. This means that there are always ample resources available, particularly at the commonly used driving speeds between 80 and 120 km/h, to ensure fast and safe overtaking.

The result of this development work is a highly efficient diesel engine with a maximum torque of 420 Nm and a power output of 205 bhp (151 kW), combined with a fuel consumption of just 6.2 l/100 km. By contrast, the D5’s predecessor generation delivered 400 Nm and 185 bhp, and yet had a fuel consumption of 7.1 l/100 km. The new five-cylinder turbodiesel has a displacement of 2.4 liters and offers excellent torque characteristics over the entire rev range, thus ensuring an exceptionally dynamic response. This outstanding performance coupled with a low fuel consumption is achieved by the use of two sequentially arranged turbochargers, a smaller KP35 high-pressure turbocharger and a larger K16 low-pressure turbocharger that completely takes over the job of providing boost pressure above a certain engine speed, thus ensuring optimum use of the available power output. “Our turbocharger technology plays a key role in the excellent driving dynamics of the D5 engine,” said Roger Wood, President and General Manager of BorgWarner Turbo & Emissions Systems.

R2S ensures higher exhaust gas recirculation rates
Compared to single-stage turbocharging, R2S increases the rated output of the engine while at the same time improving steady-state torque at low speeds and giving the engine better acceleration performance by quickly building up boost pressure. In this way, R2S resolves the conflict of objectives between achieving a high torque at very low revs and providing maximum output at high revs. At low engine speeds, the KP35 turbocharger guarantees spontaneous engine response with no ‘turbo lag’. The fast build-up of boost pressure improves pull-away torque, which has a positive influence on acceleration behavior from a standing start. As a result, the S80 can get from 0 to 100 km/h (62 mph) in a mere 8 seconds, in spite of weighing just under 1.7 tons. Apart from outstanding driving dynamics and energy efficiency, another of the key requirements for the new engine was a reduction in pollutants and particulate matter in the exhaust. The use of regulated two-stage turbocharging enables larger quantities of exhaust to be fed into the exhaust gas recirculation system. While still offering excellent dynamics, the D5 engine emits only 164 g of CO2/km and complies with the Euro 5 emissions standard.

BorgWarner Turbo & Emissions Systems is a leading global producer of turbochargers, exhaust gas return valves and other engine air management systems for passenger cars, light trucks and commercial vehicles. These systems are designed to improve fuel economy, reduce emissions and enhance vehicle performance.

Auburn Hills, Michigan-based BorgWarner Inc. (NYSE: BWA) is a product leader in highly engineered components and systems for vehicle powertrain applications worldwide. The FORTUNE 500 company operates manufacturing and technical facilities in 60 locations in 18 countries. Customers include VW/Audi, Ford, Toyota , Renault/Nissan, General Motors, Hyundai/Kia, Daimler, Chrysler, Fiat, BMW, Honda, John Deere, PSA, and MAN. The Internet address for BorgWarner is: http://www.borgwarner.com

All information Copyright © 1999-2003 Swedespeed. All rights reserved.

No photos, news stories, graphics, or Swedespeed logos may be used or reproduced without written permission.
Volvo is a registered trademark of Volvo Car Corporation and Ford Motor Company. Swedespeed is an independent media publication and is not affiliated with or endorsed by Volvo Car Corporation