- BMW M’s V8s are adopting the Miller cycle to reduce emissions.
- It means the 4.4-liter unit in the M5 drops from 577 hp to 537 hp.
- Software tweaks for the electric drive unit keep total power at 717 hp.
Euro 7 emissions regulations were watered down dramatically before they hit the statute books, but they’ve still managed to rustle a few horses, including from BMW’s M5 hybrid. The 4.4-liter V8 in the M5 and its XM Label SUV brother are both down 40 hp (41PS) as of this spring.
According to BMW, the cut applies not only across all EU member states but also in non-EU countries that adopt EU emissions standards.
Related: Facelifted BMW M5’s Fake-Nose Disguise Wants To Sow Neue Klasse Confusion
BMW is introducing multiple changes to the S68 V8s, included tweaks to the engine control software, enhanced exhaust treatment and the adoption of the Miller combustion cycle. Compared with the more conventional Otto cycle, the Miller process improves efficiency by keeping the intake valves open longer to shorten the compression stroke slightly.
Unfortunately, the bi-turbo V8’s power drops from 577 hp (585 PS) to 537 hp (544 PS) as a result. BMW hasn’t revealed what, if anything, has happened to the torque output, which currently stands at 553 lb-ft (750 Nm) in pre-Euro 7 form.
Hybrid Rescue
Yet despite this setback, BMW M claims the M5’s total system output is unchanged at 717 hp (727 PS), and that the XM Label makes the same 738 hp (748 PS) as before. And that’s not because it’s made any hardware changes to the electric portion of the plug-in hybrid powertrain. Instead, the difference is covered entirely through software optimization of the electric drive.
BMW hasn’t provided performance figures for either car in Euro 7 form, and we’d be interested to see if the acceleration numbers are also unchanged. The current M5 gets to 62 mph (100 kmh) in 3.4/3.5 seconds, and the more powerful but also even heavier XM Label needs 3.6/3.8 seconds.
Although EU lawmakers did dilute Euro 7 emissions regulations after lobbying from automakers, they are still tougher then 6e requirements. Under the new rules cars are tested over a wider range of temperatures and must achieve low emissions over a longer time period. Brake and tire particle emissions are also tested for the first time.
Facelift on the Way
We also know from spy shots that BMW is working on some visual changes for the M5 to bring it into line with the Neue Klasse iX3 electric SUV, though it looks like the brand is saving those for MY27. But all BMW models get the iX3’s new hood badge from this February and M models get updated branding.
