By on November 7, 2010

We’ve already been impressed enough with the McLaren MP4-12C’s 3.8 liter turbocharged V8 to say it “looks like mechanical sex” and give it its own gallery. The super-compact, direct-injected engine develops in the neighborhood of 600 hp, giving the new McLaren the dangly bits to show a (similarly-priced) Ferrari 458 the way around a racetrack. And though McLaren clearly thinks the MP4-12C’s race-tested abilities will help build its brand into the new race-nerd standard, it’s also beating Ferrari at a new game that will become increasingly important with time: the C02-per-horsepower game. Ferrari’s 570 hp V8 emits 320 grams of C02 per kilometer, giving the Fezza a rating of .56 grams of C02 per km per horsepower. McLaren’s goal for its not-quite finalized MP4-12C drivetrain is a C02 emissions rating of below 300 gm per km, which would give the supercar closer to a .5 gram per km per horsepower rating. And though the direct-injected, downsized and turbocharged engine helps keep that number down, the MP4-12C’s dry weight is also 176 lbs lighter than the 458’s (2,866 versus 3,042).

And McLaren isn’t alone in pushing the limits of power-per-carbon. BMW’s forthcoming Efficient Dynamics supercar will reportedly offer M6 performance (500 hp) with a third of the carbon emission of the V10-powered M6, giving it a projected C02 per km per hp figure of .454, although unlike the 458 and MP4-12C, it will meet that goal using electric engines powered by a three-pot diesel engine. Like Porsche’s 918, the Efficient Dynamics is part of the next-generation of sportscars that leaves pure-gas drivetrains behind. The future of efficiency-per-performance looks good, but only when measured in carbon. Meanwhile, the fact that BMW’s switch to a hybrid-electric drivetrain will only reduce C02 by as much as McLaren was able to improve on Ferrari’s design through downsizing, direct-injection, turbocharging and weight reduction shows how much more efficient all gas engines can be.

But here’s the real question: does carbon-per-horsepower matter? After all, 300 gm per km is still over twice the EU’s 2015 average emissions goal. The MP4-12C is no “green car,” but if you assume that supercars will continue to exist, the relationship between power and efficiency will become a more important measure over time. After all, a 89 g/km Prius breaks down to .66 grams per km per horsepower, worse even than the 458. If this new relativist perspective doesn’t take hold, government regulations will eventually become strict enough to force certain levels of performance into the realm of electric vehicles or complex hybrids. The Efficient Dynamics and 918 show that this isn’t the end of the world, but for now the MP4-12C is looking like one of the most accomplished of what may be the last generation of pure-gas supercars. Whether this technical achievement translates into brand equity and sales, however, is an entirely different question.

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14 Comments on “Does Efficiency-Per-Performance Matter?...”

  • avatar

    Whether this technical achievement translates into brand equity and sales, however, is an entirely different question.
    What also matters is the intellectual property they are creating. They could end up making far more in licensing fees from the high volume manufacturers than sales of their own vehicles.

  • avatar
    John Horner

    Once again it looks like an era of increasing fuel economy requirements may spur real progress in automotive drive trains.

  • avatar
    Paul Niedermeyer

    Not really. A simple CO2 per hp equation doesn’t really say much, or actually anything relevant. Here’s why: the CO2 output is based on the testing scheme, either the EU test or EPA test in the US. As we all know, the cars are driven very gently on these tests. So high horsepower never comes into play. These CO2 numbers tell us what these engines put out while puttering around, but tell us nothing as to their actual CO2 per horsepower at full power. That applies even much more so to high performance cars than the Prius, which is purposely horsepower limited.

    If all cars were tested at their full horsepower, we’d all be driving Priuses, because the consumption/CO2 output at full power would be many times higher than the tested level. And since the Prius’ Atkinson cycle engine is specifically a low-horsepower unit, to compare its hp/CO2 is also irrelevant.

    Modern engines, thanks variable valve timing, etc., allow them to be both quite efficient in their lower power bands (where tested) yet still deliver high performance. That’s the huge breakthrough from say thirty or forty years ago, when the choice between low speed efficiency and high performance was mutually exclusive.

    A Corvette may get the same mileage as a Malibu four cylinder at sixty mph: now drive them both at their respective top speeds (full horsepower): the Corvette will then probably drink three times the fuel per mile as the Malibu.

    That’s the whole reason the super car makers are going to hybrid, KERS, or whatever, in order to bring down the tested CO2 numbers. What these engines/cars actually put out in terms of CO2 at their full horsepower ratings we’ll never know, unless someone bothers to test them.
    “Gaming” the testing standards is old hat; the Corvette has been doing it for decades with its 1-4 shifter. Now the game is being notched up, substantially. and the supercar makers have little choice but to employ the latest technological tricks, regardless as to their actual relevance in terms of how much they emit when full horsepower is used./p>

  • avatar

    Since western governments started taking efficiency more seriously and have raised the bar on fuel consumption, it does matter. Even though many (including TTAC) have been rallying against increased standards by painting them as the death of automotive fun and raising consumer costs, it is the engine that is driving innovation and progress is transportation technology.
    Most luxury automakers don’t mind this trend as it gives them a chance to differentiate themselves from other players by using their large R&D budget to deliver high tech products that meet higher consumption standards as well as deliver the driving enjoyment and performance consumers want.

  • avatar

    Who cares about these limited low mpg machines CO2. If they really cared more they’d suggest their customers get mental help.

  • avatar

    If a carco/conglomerate has to average its total carbon output across a range of models, then YES.
    Also, if the dev trickles down to more pedestrian transports, it can further transform our daily-drivers into cars that will preserve airspace for sportscars, gts or the uncommon supercar, because the high-frequency masses will have banked so much carbon savings en-bloc.
    If I could drive a supercar on the weekends in the summer, I’d be happy to drive a Polo BlueMotion or ride a bicycle to work during the week.
    Of course, there is no yet-acceptable measure of my personal carbon-footprint while on the bicycle.
    And naturally, the conclusion by all ecomentalists for the ultimate planet-preserving carbon savings is to wipe out the entire human race; and cows too; they fart out too much methane.

  • avatar
    Uncle Mellow

    I know they are dirty and smelly , and don’t make the right noise , but BMW make some almost-super cars with diesel engines that have huge power with low CO2. Audi even tried putting a diesel in the R8.

    • 0 avatar
      Brian P

      The newly-developed high-performance diesels are most certainly neither dirty nor smelly. For what it’s worth, the Audi LMP racing cars with diesels have DPF catalysts – the technical regulations prohibit the engine from making visible smoke. It’s true that the Audi (and Peugeot) turbodiesel racing cars are unnaturally quiet …

  • avatar

    It’s remarkable what happens when a company truly turns the engineers loose on a design.

  • avatar

    If you’re trying to measure ‘efficiency-per-performance’ then BSFC (Brake specific fuel consumption) is the correct measurement, CO2 per km would be a measure of  ’emissions-per-performance’ (to continue the rather awkward and inelegant phraseology).

  • avatar

    No it doesn’t matter. It is a completely misleading measurement.
    They are NOT measuring (C02 at Max HP)/Max HP. Which might actually be some kind of efficiency, but still of dubious value.
    Instead, they are measuring (C02 at low HP)/Max HP. Which is complete BS marketing nonsense.

  • avatar

    Why does CO2 per hp matter?
    One, it’s a direct measurement of fuel efficiency, so it doesn’t really differ from L/100km or MPG save for it’s measuring hydrocarbons on the way out.  So other than feel-goodness it’s kind irrelevant as well already have a fuel usage yardstick.
    I’m not a chemist, so maybe I’m missing something, I don’t see why this would be useful unless you’re going to replace fuel usage metrics we already have.
    Second, and this concerns me, wouldn’t this lead to gaming of the system by favouring learn-burn?  Assuming you could get by emissions regulations for NOx?

    • 0 avatar

      The only advantage it has over L/100km or mpg is that it is a consistent measure of environmental impact over all sources of fuel.  Diesel has more carbon per gallon than gasoline, and both have more carbon per gallon than ethanol.  So even though diesel gets better mpg, it’s CO2 emissions aren’t as big of a jump.

      Here in the US, where almost everything uses gas, it’s irrelevent.

  • avatar

    WTF? What a meaningless metric this is. Why hp and not say top speed, weight or vehicle cost.

    Multiplying the CO2/Km by the average distance driven might come down legitimately in the favour of a super-car. but CO2 /hp is ridiculous, by this measure a top fuel dragster might be fairly frugal given they use nitromethane not petrol (different stoicometric).
    While we’re at it express the average distance driven in furlongs to maintain the mish-mash of SI and Imperial units.

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