Three turbochargers give BMW extra power
BMW is offering its most powerful diesel to date in the revised X6 and the X5, known as M50d models. The engine is the familiar 3-litre straight six layout, this time, and a first, with three turbochargers. One of two small turbochargers starts blowing at engine speeds just above idle, giving “instant response” to any movement of the accelerator. As the revs increase to 1,500rpm the exhaust gas reaches the large turbocharger, ensuring that peak torque of 545 lb-ft is attained and maintained from 2,000rpm until 3,000rpm. At 2,700rpm a vacuum-modulated exhaust flap opens allowing exhaust gas to flow past the second small turbocharger creating additional charge pressure, allowing maximum power of 376 bhp to be available from 4,000 to 4,400rpm. If the large turbocharger is spinning at particularly high speeds a vacuum regulator opens a wastegate valve to relieve pressure and so avoid unwanted exhaust back pressure.
The X6, with a revised face and other detail changes, goes on sale on June 16, priced from £46,725. The high performance M50d model costs £62,260 and is quoted at 36.7mpg, 204g/km of CO2 and 0-62mph in 5.3 seconds. The X5 M50d has similar figures but managed 199g/km of CO2 and costs £60,325.
BIGGEST BOOST: The new BMW X6.