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posted by martyb on Thursday July 26 2018, @06:55PM   Printer-friendly
from the opposition-is-growing-stronger dept.

Submitted via IRC for SoyCow1984

Horizontally-opposed engines are often referred to as “boxer” engines because the motion of the pistons sort of resembles a boxer, punching. Really, though, if any engine should be named for a boxer, it’s the other kind of opposed engine: the kind where the pistons actually “punch” right at each other. They’re called opposed-piston engines, and they’re fascinating.

Opposed-piston engines are not new at all; they’ve been around since the late 1800s, and even earlier in steam form. In fact, the famous Civil War ironclad USS Monitor used a variant of an opposed-piston engine known as a “vibrating lever” engine.

Essentially, an opposed-piston internal combustion engine is a two-stroke engine with no cylinder head, two separate crankshafts, onto which two sets of pistons are connected, with the pistons sharing one cylinder.

The pistons meet (well, nearly meet) at the center of the cylinder, the top dead center (TDC) for both pistons. ports on the sides of the cylinder let fuel/air in and exhaust out, and are exposed by the motion of the piston.

[...] What’s especially notable about the engines is that, in three-cylinder (remember, six-piston) form, the Achates Power vertically-oriented opposed-piston diesel engine shown in the video there managed to obtain thermal efficiencies in the high 40s/low 50s percent. Keep in mind that a conventional four-stroke diesel engine will only be about 35 percent thermally efficient, on average. That’s a big bump.

Source: https://jalopnik.com/its-time-to-learn-about-wonderful-and-weird-opposed-pis-1827804895


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  • (Score: 2) by JoeMerchant on Friday July 27 2018, @12:31AM

    by JoeMerchant (3937) on Friday July 27 2018, @12:31AM (#713474)

    I've been impressed with some of the modern SUV's I've rented: big as a whale and gets 30mpg at 80mph. Still not worth the entry price, but those chilled seats were nice. I think that one had VD (most hillarious marketing gaffe of the past 30 years: Variable Displacement.)

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