When a vehicle manufacturer is looking to revise its engines, increasing power and torque are typically right at the top of the wish list. However, BMW set itself different objectives when updating its four-cylinder diesel units. Its focus was on optimizing consumption and emissions, while at the same time improving response and dynamic driving performance. The developers were able to achieve both objectives, in particular through use of a two-stage turbocharging system from BorgWarner.
Fit for Euro 6d-TEMP
It comprises a smaller waste gate turbocharger, which as the high pressure stage secures faster pressure build-up and thereby also faster torque generation from very low revs and exhaust gas rates. As the engine speed increases, an ultramodern VTG turbocharger then takes over as the low-pressure stage and effectively transforms the exhaust gas energy into more power. The driver feels the effect of the R2S® system in the form of significantly more dynamic pickup in response to gas pedal commands. This extra dynamic driving performance is also associated with an increase in efficiency. The EU fuel economy in accordance with NEDC, and thereby also the CO2 emissions of the current B47, are four to five percent better than those of the predecessor engine. In addition to this, the two-stage turbocharged turbodiesel unit also complies with the strict Euro 6d-TEMP emissions standard.
The engine with the designation TwinPower- Turbo has a displacement of 122 cubic inches in all versions. The 18d version delivers 147 hp (110 kW) and maximum torque of 236 lb-ft (320 Nm), which is already available from 1,500 rpm. The 20d version generates a maximum of 187 hp (140 kW) and delivers up to 295 lb-ft (400 Nm) to the drive wheels.
Breaking new ground in manufacturing
The turbocharging systems for the BMW unit are manufactured at BorgWarner in Kirchheimbolanden, Germany (see also the article entitled “Smart Automation” in TurboNews 1/2018). The turbo specialist set up a highly automated modular manufacturing system for the turbochargers used in the R2S® system. This guarantees both a high degree of flexibility and high space productivity at the location. Since launch, production has been significantly extended. This platform engine is ultimately used worldwide in a very wide range of BMW and MINI vehicles.
The R2S® system from BorgWarner is assembled using an automated modular manufacturing system
Photo: © BorgWarner