• BMW has built some amazing turbodiesel engines in its time.
• The powerful 3.0-litre quad-turbodiesel engine's era is coming to an end.
• The niche high-performance diesel engine plays too small a role in BMW's strategy.
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BMW has decided to call time on its amazing quad-turbo engine and M50d models.
There is no question that the greatest BMW engines usually have six cylinders and displace 3.0-litres.
For decades BMW has endured this configuration and proven that for linear power delivery and smoothness, it is unrivalled.
While V6 engines are shorter and easier to package, saving valuable design space above the front wheels, the protocol at BMW has always been to allow engineers to have the final say. As such, the company has remained committed to in-line configuration six-cylinder engines.
Fans of the brand don't often associate BMW with diesel, but the Munich company has built some fantastic turbodiesel engines. And none more special, than its B57D30S0. To some that engine code might not appear to have much significance, but if you are a follower of all things turbodiesel, it is the engine recognition code without compare.
Going fast – and far
As the demand for larger luxury SUVs increased, BMW had a problem. With customers demanding 5 Series performance from their heavier and less aerodynamic X5/X6 SUVs, more engine power was required.
The solution would have appeared simple enough: just add turbochargers. But there was an additional issue to consider: range.
Luxury SUV customers wish to explore more adventurous routes, and that meant a requirement for both surging performance and outstanding open road cruising economy. BMW's engineers developed a typically inspired solution, the 3.0-litre quad-turbodiesel.
If two or even three turbochargers were good and great, then four had to be best. Technical constraints were significant when developing the quad-turbo B57D30S0 engine. Harmonising all four turbochargers to be both efficient and powerful, depending on driver input, would require meticulous engineering and control software coding. Managing the heat build-up and cooling was even more complicated.
With a proud history of trick engine development, BMW's engineers delivered. Originally launched in 2016, the 3.0-litre quad-turbodiesel truly found its purpose as an M50d engine for all BMW's large SUVs: X5, X6 and X7.
BMW managed to get 294kW and 760Nm out of the engine, which meant that even a gargantuan 2460kg X7 M50d felt quick off the line and could deliver very safe margins of overtaking acceleration.
Sheer performance was only part of the quad-turbo B57D30S0's appeal. In an X5 M50d, owners could confidently expect cruising fuel consumption of just under 7.0-litres/100km, which equated to a theoretical 1 000km tank-to-tank range.
Why is it being discontinued?
For an engine which is so excellently suited to the purpose of powering large SUVs, one would expect the 3.0-litre quad-turbodiesel to have a guaranteed future. But this is, sadly, not the case.
Despite luxury SUVs now accounting for most of BMW profits, the company will be retiring its B57D30S0 engine this September. No matter your brand affiliation, this is a poignant moment for diesel power fans, as there will in all likelihood never be another quad-turbodiesel production engine.
Why is an engine of such incredible technology, with an outstanding performance-to-economy blend, being withdrawn? Like many other German luxury vehicle brands, BMW is under pressure to electrify, and the R&D costs associated with their battery vehicles are draining resources.
BMW has always been a company which prides itself on engine development, and its B57D30S0 is a clear example of that. The reality is that although many X5, X6 or X7 customers select a 3.0-litre turbodiesel engine option, very few of them choose the M50d quad-turbo configuration.
As a niche high-performance diesel engine, it is simply too small a part of BMW's business to justify its complexity into the next decade.