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2017 BMW 750d xDrive Launched with 400 HP Quad-Turbo 3-Liter Diesel

There are two things you can't have enough of in the car business: turbochargers and exhaust pipes. BMW just launched the most badass diesel flagship sedan ever, the 750d xDrive that has as many turbochargers as a Bugatti Chiron.
2017 BMW 750d xDrive 1 photo
Photo: BMW
As predicted, the first car to get a quad-turbo 3.0-liter diesel engine is the biggest and newest model from BMW, the 7 Series. This new 750d model is rated at 400 PS (394 bhp) and 561 lb-ft (760 Nm) of torque offered between 2,000 and 3,000 rpm.

Of course, BMW isn't the only company with a powerful diesel engine, as Audi just launched the SQ7 SUV with a 4.0 TDI that has two (sequential) turbochargers and an electric compressor. That engine is sure to find its way into the next A8 sedan, probably in 2017.

That being said, we have to admit that the power density is amazing, the best of any 3.0-liter diesel engine. BMW has given slightly negative revisions to the 0 to 100 km/h sprint time, as the 750d xDrive is said to take 4.6 seconds, not 4.5s. As for the long wheelbase model, it requires 4.7 seconds.

In both cases, these figures are 0.3 seconds better than the predecessor model. Which one? The old (F01 series) 750d xDrive was equipped with a tri-turbo 3.0-liter engine; the same 381 PS unit found in the X5 M50d.

It might be worth noting that the only other 7 Series you can buy with a diesel engine at the moment is the single-turbo 730d, capable of reaching 100 km/h in 5.8 seconds when equipped with xDrive.

Just like with the M140i and M240i, it's a case of small improvements in all directions. The new 750d is said to be 5% more powerful and 11% more economical than before. It's like having a little bit of cake and eating it.

The fact that this engine makes almost as much power from 3 liters as a Camaro does from more than double that is impressive. However, the torque is what most people buy these models for. While the maximum 760 Nm is available only between 2,000 and 3,000 rpm, you can have 450 Nm from 1,000 rpm. That said, the SQ7 packs all its 900 Nm from 1,000rpm from its bigger V8 thanks to the electric compressor.

Turbocharging adds power, but it doesn't necessarily decrease the fuel consumption. However, BMW has lots of experience with the high-pressure injection systems and tricky cooling that comes with this type of diesel engine. They are, after all, the first to launch a tri-turbo unit as well!

Special features of this engine include the now five-layer cylinder head gasket, cylinder bores with a twin-wire arc-sprayed coating and pistons made from an aluminum/silicon alloy with remelted bowl rims, bronze liners in the pin eyes and centrally controlled cooling. The injectors are also new, running at 210 bars instead of the old 200. Also like the M140i, they've placed the particulate filter and NOX storage catalytic converter closer to the engine. Perhaps the most novel feature is that there are two exhaust gas recirculation systems, one for the low-pressure stage and another for the high one.

As for the quad-turbo system, this includes two very small turbos with variable turbine geometry integrated into a single housing. The gigantic turbo used by the tri-turbo engine has been replaced by two smaller ones. This results in a better response time.

Usually, the two low-pressure turbochargers and one of the two high-pressure turbos are permanently in action. Only under hard acceleration from idle will the two low-pressure turbochargers be bypassed using a flap control system, thus allowing boost pressure to be built up quickly. Under normal conditions, the second high-pressure turbocharger is brought into play at an engine speed of about 2,500 rpm.
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About the author: Mihnea Radu
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Mihnea's favorite cars have already been built, the so-called modern classics from the '80s and '90s. He also loves local car culture from all over the world, so don't be surprised to see him getting excited about weird Japanese imports, low-rider VWs out of Germany, replicas from Russia or LS swaps down in Florida.
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