• Luke Posted: 6/23/2009 9:35am PDT

    "Is there some inherent inefficiency to a flat four engine compared to an inline four?"
    This flat 4, makes 170hp. You are comparing wimpy Accord and Camry engines, that make 140hp, and identical gas mileage, to a flat 4 with 4wd that has 170hp. 1st gen Subaru with front wheel drive, and 130hp, got 22/32 mpg. Thats when Accord with less power got 22/30 mpg. I know from experience, I owned both.

  • Bengt Halvorson Posted: 6/18/2009 9:51pm PDT

    Carl,
    Over the years I've asked a range of powertrain engineers this question, and the simple answer is no one configuration (in-line, V, or flat) is naturally more fuel-efficient. I have been told in the past that the individual banks of a V-6 will reach peak operating temperature sooner than an in-line 6, and it's easier to maintain that peak temp for emissions, but I've been told more recently that many of those issues were solved with modern alloy blocks and heads and controls. You could make the argument that flat and V engines expose more surface area to the outside air, but I don't think you could easily conclude that they're less efficient.

  • Carl F Thelin Posted: 6/18/2009 7:22pm PDT

    Lets think about this as engineers. I have not, yet, given a lot of thought to this question - Is there some inherent inefficiency to a flat four engine compared to an inline four? I would guess so offhand but have not yet given it a thorough analysis. Has any other reader of TCC done it yet?