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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
(Score: 5, Interesting) by LoRdTAW on Thursday July 26 2018, @10:29PM
This is why I can't stand sites like Jalopnik, shitty writing for the sake of writing an article to generate page hits. Guess this person never heard of the Detroit Diesel 2 strokes. You could find the Series 53, 71 and 92 in shit loads of 60's/70's/80's trucks. In fact, the sound of a 6V92 is the standard TV/hollywood bus sound they dub in. Anyone who has sat in a GMC bus knows that sound and the big clouds of black exhaust they belched as the rings wore. Throughout high school I took the Q41 bus to school and the NYC bus companies (Green Lines ran the Q41) all ran GMC's powered by 6v92's until the MTA took over. Many were repowered by Series 50's, a 4 banger version of the 12L 6 cylinder series 60, in order to improve air quality. It was not uncommon to a face full of thick diesel exhaust laiden with soot when waiting at the bus stop.
The Detroit Diesel 2 stroke series: 51, 53, 71, 92, 110, 149 have been around since 1939 when the company was started under GM. About 4 million of those engines were produced for various markets and parts will be available until 2040. Their weakness was oil ingress into the combustion chamber because of the scavenger ports at the lower portion of the cylinder which introduce air under pressure from a roots blower and sometimes boosted by a turbocharger. The action of the rings passing over the ports would allow some oil to make its way into the air stream and burned during combustion. And it got worse as the piston rings wore. If these guys solved the oil ingress problem then they have achieved what Detroit Diesel tried and failed to achieve for decades. That was one of the main problems with their design and that eventually led to them scrapping the 2 cycles as it was impossible to meet the emerging EPA emission standards. Perhaps there are some modern materials or designs that simply weren't available at the time when Detroit was working on them.
I remember one trucker saying something like "When I ran Detroit's I always kept spare oil, belts, oil, filters, oil, and more oil." They loved burning through it. Another issue was "slobbering"; it was not uncommon to see a trailer pulled by a detroit powered tractor with a big greasy soot streak near the exhaust stack opening. Some of the oil was partly combusted or escaped unburnt and made a mess. They also leak oil from everywhere. Though I will say this, I absolutely love the sound of them. I tried buying an old Mack WS Cruiseliner that was a former fire pumper which was 6v92 powered but the engine was blown and I didnt have the $2000+ to have it towed to NYC from down south. Wound up buying a B61 but that WS was my missed opportunity that I can't stop thinking about. Second picture, the red cab-chassis: https://www.trucksplanet.com/catalog/model.php?id=398 [trucksplanet.com] Sigh. Long frame and day cab with a detroit which is rare. I'd have added a 12k pusher axle, put a 20 ton hook lift on it with a flatbed body, and heavy pintle hitch on the rear. The paint job would be black out with HID headlamps and black out chrome accents. Strait pipe it and let the little 6v92T scream down the highway. Wound up buying a running B61. Anyway, I digress...