With the 2013 BMW M5 finally going on sale in the U.S., we definitely saw this coming. BimmerBoost recently got a hold of engine dyno run for the new M5, and is reporting that the car's twin-turbo V8 is "severely" underrated.

Officially, the M5's 4.4-liter V8 is rated at 560 horsepower and 500 pound-feet of torque, but the dyno graph reveals numbers at the rear wheels to be 527 hp and 476 lb-ft in completely stock form. While the idea of the engine being underrated is just an assumption, the general rule of thumb is a 15-percent drivetrain loss – if accurate, the new M5's losses would be just six percent. Using the 15-percent rule, the 2013 M5 would lay down 476 hp at the wheels.

The idea of BMW underrating its engine outputs is nothing new. Earlier this year, the new 328i show some impressive numbers of its own.


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  • 36 Comments
      • 2 Years Ago
      [blocked]
      aviboy97
      • 2 Years Ago
      BMW is not underestimating the power of their engines. Every time I see an article like this, it is really disturbing that journalists do not do more homework about what they are writing about. BMW has employed technology they call "Efficient Dynamics". This encompasses various technologies that increase fuel economy and finding ways to reduce engine friction and engine load. The result of this means less power is wasted down to the wheels as well as improved fuel efficiency. So, the old assumption of 15% drive train loss is completely irrelevant. A BMW M5 has nothing in common with a 1970 Camaro that had 15% drive train loss.... Mazda has also employed such technologies with Skyactiv Technology. Another focus of this technology is up to 40% reduction in engine and transmission friction. Guess what, that means more power to the wheels. Please, autoblog writers, do some homework before you post another "underestimated power" article.
      clquake
      • 2 Years Ago
      Instead of wild speculation, why not just take the engine out and dyno it at the flywheel. Then you'd have a more accurate and complete article.
      spdracerut
      • 2 Years Ago
      An European mag dyno tested the M5, Porsche Panamera Turbo S, and E63 AMG about half a year ago. Keep in mind, typical Euro dynos are set to report estimated flywheel horsepower based on coast-down drivetrain loss data. BMW M5 = 620hp, claimed 560 Panamera Turbo S = 555hp, claimed 550 MB E63 AMG PP = 610hp, claimed 557 Just google M5, AMG, Panamera turbo S dyno to find the full article.
      XT6Wagon
      • 2 Years Ago
      only driveline losses are not a %. Do you really think the transmission is absorbing 100+hp? If they were we would see the transmission and rear diff have cooling systems on par with a sub-compact car's engine. Rather they eat a nearly fixed amount of HP in modern drivelines as long as its a solid mechanical link. (unlocked torque converters are different story). The HP lost is also a function of RPM. Limited Slip diffs, Torque biasing systems, and the like can consume more driveline power, as evidenced by the increased thermal loads on the transmission, transaxle, or axle they are in. If you ever want to really get a grasp on where and how much power is being lost, look at where heat is being generated in the driveline.
        huisj203
        • 2 Years Ago
        @XT6Wagon
        I've wondered the same thing. Back when cars pretty much all made between 100 and 200 horsepower, and the amount of power scaled pretty well with the size of the engine (and likely the size of the transmission), maybe the straight lop-off-a-standard-percentage estimate worked fine. But with engines getting more and more powerful and with more focus on precision and efficiency with transmissions, it seems like those estimates may be out of date.
          Agilis
          • 2 Years Ago
          @huisj203
          Same as well. Always wondered how reliable these estimates are, especially after you hear contradicting statements from owners against the manufacturer's claims.
        Agilis
        • 2 Years Ago
        @XT6Wagon
        Forgive me, might be out of place here as I'm not as knowledgeable as you, so please correct me if I'm wrong, but I do know that my Audi S5 horse power claim is not true because it's equipped with Audi Quattro which causes significant power loss.
          Nick
          • 2 Years Ago
          @Agilis
          Probably closer to 15 or 16 %. Modern Haldex / Borg-Warner based Quattro systems are remarkably more efficient than they were 10+ years ago
        Cory Stansbury
        • 2 Years Ago
        @XT6Wagon
        It's important to note that it's a combination of a fixed and variable loss. Fixed losses would include windage losses of the gears spinning in the oil and non-load bearing losses. However, the largest losses are caused by the friction between the gear tooth faces as they slide past one another. These scale directly with input torque. So, perhaps it's 2% for fixed and 10% variable for most modern manual trannies and rear diffs? Just a guess.
          Cory Stansbury
          • 2 Years Ago
          @Cory Stansbury
          To be more clear, maybe it's RPM dependent on windage/bearing losses and torque dependent on the variable losses. Could be 10 HP of windage losses in 4th gear at 130 mph plus .1*engine power= total drivetrain loss just as an example.
      Camaroman101
      • 2 Years Ago
      never trusted dyno numbers(except engine dynos) ever since an article in a magazine i read (hot rod?) anyway they took a super snake gt500 around to 6 different dyno shops and got hp numbers ranging from 560-640hp. dynos should only be used to tune and test the hp difference from mods
      scraejtp
      • 2 Years Ago
      Anyone who thinks a modern RWD high power vehicle has a 15% drivetrain loss at peak power is an idiot, especially in 4/5th gear. (1:1)
      Macvicar24
      • 2 Years Ago
      Too bad the price tag isn't overrated. They meant to sell it for 15% less.
      • 2 Years Ago
      [blocked]
      wafflesnfalafel
      • 2 Years Ago
      I still wish the new 5 wasn't quite so big on the outside - but love the updated technical data, we are so f'n confident in our machine we are going to underrate the specs by 60-70 hp just to leave everybody guessing - that's the kind of swagger BMW has been missing for a while. It really does the original M5 justice, (the press cars should be black instead of that dayglow blue.) I am even coming around to the DSG boxes - heard one of the current model M3 snap off a couple downshifts getting on the freeway the other day - as beautiful as angels singing.
      KO
      • 2 Years Ago
      Is it under-rating, or better drivetrain efficiency? I've had my lowly E46 325iT on 2 DynoJets under different conditions and got 171RWHP (184 mfr spec; 7% loss).
        montoym
        • 2 Years Ago
        @KO
        I'm inclined to believe that's really what's happening here. Considering all the other advances in vehicle technology, to assume that all these years later we still have a 15% driveline loss is asinine. Aren't there ways to test the driveline loss on a dyno (coast-down testing I believe)? Why don't any of these claims of underrating ever come with a coast down test too? I think I know the answer to that one though.........
      seminiferus
      • 2 Years Ago
      I think this article could have been worded differently and more clearly.
        • 2 Years Ago
        @seminiferus
        [blocked]
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