Tuesday, 21 July 2015
BorgWarner named as VW turbo supplier
When Volkswagen introduced its high-performance 2-litre diesel, engineers adopted a twin-turbocharger layout; quite different to the simplified in-house single-turbo route taken by Daimler for its OM 471 truck diesel engine.
Engineered to comply with Euro 6 emissions standards, the 2-liter four-cylinder engine is the most powerful diesel engine in its class. Providing an output of 176 kW (240 bhp) and a maximum torque of 500 Nm, it achieves an average fuel economy of 5.3 litres/100 km.
Volkswagen has made no bones about the fact that it wants to set performance benchmarks in mainstream diesel engine development; the first step being the four-cylinder engine based on a twin-turbocharger system and high pressure common rail system.
The engine in the Passat has a specific output of 88kW/litre, but much higher ratings are planned.
VW Group's head of engine development, Dr Heinz-Jakob Neußer, has said “We will start with a 2-litre engine with 500Nm. This has a 2,500bar injection system and it can comply with all emissions standards.”
The unit is part of the EA288 diesel engine family and the single variable geometry turbo version develops 140kW/380Nm, figures that are eclipsed by the 176kW/500Nm variant.
In addition to the dual-stage turbos and the 2,500bar rail pressure, a close-coupled after-treatment system featuring SCR, together with high- and low-pressure EGR systems ensure Euro 6 compliance.
VW is looking to stretch the ratings as high as 100kW/litre – exceeding those of most advanced six-cylinder diesels – but is also looking at variants in between. For those featuring only one turbo, VW might select electric superchargers.
“Within 300 milliseconds they can go up to 70,000 rev/min, and then for a few seconds you get an additional boost so the turbocharger revs up very quickly,” Neußer has said. “And you have the big advantage that you have an air surplus – this is very important for emissions performance. We are working very hard….. and you will hear a lot from us in the future.”
Commenting on its disclosure as turbo supplier for VW’s 2-litre diesel, Frédéric Lissalde, president and general manager, BorgWarner Turbo Systems, said “We are pleased to expand our long-term partnership with the Volkswagen Group by delivering our regulated two-stage turbocharging technology for this powerful, downsized diesel engine.”
“BorgWarner's leading turbocharging technologies help automakers deliver powerful performance,” he added.
BorgWarner’s turbocharging system consists of two series-connected turbochargers and features a variable turbine geometry (VTG) turbocharger for the high-pressure stage combined with a larger B03 water-cooled turbocharger optimized for low-pressure exhaust gas recirculation (LP EGR).
The low-pressure EGR is captured downstream of the exhaust emission control system and then mixed with the fresh air upstream of the compressor of the low-pressure stage.
BorgWarner says it uses a special protective coating on the turbocharger compressor wheel to withstand the extreme loads and the corrosive particles.
Controlled by an electric actuator, BorgWarner’s VTG turbocharger responds quickly at low engine speeds, resulting in a rapid rise in boost pressure for “nearly instant acceleration”.
As engine speed increases, both turbochargers work together, gradually shifting to the larger, low-pressure turbocharger. At higher engine speeds, all gases flow directly to the larger B03 turbocharger, maintaining smooth power delivery at higher speeds.
By combining two series-connected turbochargers of different sizes, BorgWarner claims its R2S technology provides high boost pressures over the entire engine speed range.