You’ve probably noticed I’ve been on an automotive kick lately. Don’t worry, I don’t think I’m in any danger of becoming a babbling gear-head. Firstly, I don’t have the patience or mechanical skill to actually put an engine together without blowing myself up and setting the neighborhood on fire. Secondly, where I live, working on cars isn’t a cheap hobby, and the fact that I’m considering going to grad school means all my pennies are spoken for.

I’m interested in engines the same way a little boy would be. They’re big, loud, powerful, complicated, and mechanical. I could probably come up with fancy reasons for being curious about engines, but the fact is, I just like them. But I like them in kind of a shallow way. The more intricate details of engines still confuse me. There’s a reason I call myself Hobo Sullivan: in pretty much all the areas I talk about, I’m like a hobo being dragged into an art gallery. I can say “That painting looks like shit” or “That’s a really pretty painting,” but if you start trying to teach me about composition or Postmodernism, my eyes’ll glaze over and I’ll start asking when I get my bowl of soup.

Which is a really long-winded way of saying that this post isn’t intended for engine experts. If you’re into engines, you probably know every single thing on this list. This is a post for people who are casually interested like me. This is me emerging from the Google Caves with a handful of funny-shaped crystals and saying “Look at this cool stuff I found!” This list has nothing to do with with deciding on the best engine or anything fancy like that. This is a list of the engines I’ve found in my bizarre curiosity that made me say “That’s kinda cool…”

The Boxer-6

(Image from CarThrottle.com)

The boxer-6 isn’t all that weird, since it’s still in common use. That’s partly because you’ll find it in sports cars like the Porsche 911, and in some of Subaru’s current cars and SUVs. When I first started learning about weird engines, I thought the boxer-6 was just a V6 where the V got all flattened out. Engines like that do exist, but they’re not called boxer-6s. The difference is, in a boxer-6, pairs of pistons opposite each other move in and out simultaneously. Unlike in a lot of V-engines, each piston’s connecting rod has its own bearing on the crankshaft. What does any of this matter? Well, it’s unusual, for one. For two, the peculiarities of engine dynamics (which I don’t pretend to understand) make the boxer-6 a very smooth-running, well-balanced, low-vibration engine. Also, the fact that its cylinders aren’t crammed cheek-to-cheek in a V means that even fairly high-power boxer-6s can be air-cooled (though some are still water-cooled).

But you guys know me by now. You know I always go to extremes if given the chance. I’m not going to be satisfied with a six-cylinder engine, no matter how nice.

The H-16

(From Wikipedia.)

We’ve made quite a leap. While you could go out right now and buy a car with a boxer-6 in it, the only way you could have an H-16 engine is time travel, or by being an insane millionaire and having one built for you.

The engine above is British Racing Motors’ H16 engine. There are plenty of weird, esoteric terms used in automotive circles, but the weird letters that show up in engine names are perfectly sensible (mostly). My car is powered by an I4 engine, which means it’s an inline-four: four cylinders in a straight line. A V6 has six cylinders in two banks of three, with the pistons angled so that their connecting rods form a V-shape, with the crankshaft at the tip of the V. You’d refer to the boxer-6 above as an F6, for flat-6.

What, then, is an H16 engine? Well, it’s horrifying, is what it is:

(Again, from Wikipedia.)

An H-16 is two flat-8s stacked on top of each other, each with its own crankshaft. The crankshafts are connected at the end by gears. Like I said, I don’t know engines, but that seems like a bad idea.

For some applications, it’s actually not. H-engines are mechanically pretty well-balanced, for one. For two, they’re a bit more compact than, say, a V-engine with the same number of cylinders, which made them popular for high-power airplanes.

But car enthusiasts will know that the H16 I showed at the top of the section didn’t come from an airplane. It came from British Racing Motors’ ill-fated P83 Formula 1 car, which has a peculiar, and if you ask me, slightly unpleasant sound.

BRM’s H16 was plagued with problems. For one thing, having two sets of cylinder heads on opposite sides meant it needed two radiators and a split fuel system. It also needed dual camshafts (which are the mechanical clockwork-type devices that tell a cylinder’s valves when to open the intake valves and let in fuel, and when to open the exhaust valves to let out burned fuel). It needed dual camshafts for each cylinder head. That’s bad enough in a V-engine, where you have two cylinder heads, but the H16 had four. For another, it was more complicated and fuel-hungry than even its competitor, the mighty V16. Unsurprisingly, the engine wasn’t a success, partly because a lot of them just blew up during races. Apparently, British Racing Motors’ troubles at the time, and their obsession with complicated engines, earned them the nickname “British Racing Misery.”

Still, it’s a weird, interesting engine, and somebody had some serious gonads to say “You know what? A V16 is just too damn simple.”

The Napier Deltic

(From Wikipedia, again.)

You remember that scene in the first Back to the Future where Dr. Brown is talking about inventing the Flux Capacitor? “I slipped, hit my head on the edge of the sink, and when I woke up, I drew this.” I’ve gotta figure a bonk on the head inspired the Napier Deltic. For those who don’t know much about engines, let me explain why the picture above shows one of the weirder engines ever invented.

1. Opposed pistons. In a common piston engine, the air-fuel mixture burns, and the pressure from the hot gas pushes a piston down, which applies torque to the crankshaft, which drives whatever machine the engine is running. There’s just a cylinder head holding the hot gas in. In an opposed-piston engine, though, there isn’t a cylinder head, but rather, two pistons in a headbutt configuration in every cylinder. The fuel-air mixture enters the space between the two heads and burns there, pushing the two pistons apart, driving two crankshafts.
2. The delta design. As you can see, the Deltic isn’t even as simple as a regular opposed-piston engine. That picture shows three cylinders, containing six pistons, driving three crankshafts. It’s weird, but it’s got a certain geometric appeal to it. It was also, apparently, a lot more compact and powerful than similar engines of the time, which made it attractive for British torpedo boats and locomotives.
3. It was a two-stroke. If you don’t know, two-stroke engines are usually what you find powering small power tools like weed-whackers and chainsaws.The engines of most modern cars are four-stroke. The differences are subtle. In a four-stroke engine (which most gasoline engines are), the piston has to go up or down a total of four times to complete a full cycle: It moves down to suck in in air and fuel, moves up to compress the air and fuel before ignition, is pushed down by the burning air and fuel, and finally rises up to push out the exhaust. In a two-stroke engine, the intake and exhaust steps happen at the same time: often, the piston pushes down on a fuel-air mixture in the crankcase, and the pressure pushes the mixture into the engine, which pushes the exhaust out. The major advantage of a two-stroke engine is that it doesn’t need mechanically-operated intake and exhaust valves, since the piston controls intake and exhaust. This saves weight and complexity, which is vital when your engine is powering, say, an airplane, or a boat, or a chainsaw that needs to be light enough to hold up for long periods, without getting tired and dropping it on their foot.

The Deltic was fairly successful, since it packaged eighteen or more cylinders (two pistons each) into a smaller package than was possible with other designs of the same cylinder number. It was a lot lighter than comparable engines, too.

Why aren’t there more Deltic-type engines around? Well, a little research suggests that’s mostly because Napier was bought out after World War 2, and switched to making things like turbine engines and turbochargers, the former of which were rapidly filling a lot of the niches the Deltic once occupied. I suspect the peculiarity of the delta design also played a part, since my first reaction to it was “there’s no way that was a success.” I was wrong about that, but I bet the Deltic scared off more than a few mechanics.

The W12

(Still Wikipedia.)

We’re not done with Napier yet. Above, you see the Napier Lion.

Although it’s not entirely accurate, you wouldn’t be far off if you described a V8 engine as two I4 engines driving the same crankshaft. The Napier Lion is a broad-arrow W12, which is what you’d get if you took a V8 and jammed another I4 down the V (sounds like a weird fetish fantasy…)

You’ve probably heard of W engines before, even if you’re not into cars. A W16 is the powerplant behind the Bugatti Veyron, which is famous for two things: holding the Guinness record for fastest street-legal car, and being a rare example of a supercar that isn’t absolutely horrible to look at. (I mean, it’s still not great, if you ask me. It looks like ergonomic furniture. But look at a Lamborghini Aventador and tell me the Veyron isn’t better-looking, if only because it’s not as…pointy.) But the W16 in the Veyron is a different type: it has two banks with eight cylinders each, and those cylinders are jammed just about as close as you can get them. Each of the banks is essentially a VR8: a V8 with a very narrow V. Since it only has one crankshaft, W isn’t exactly a good letter to use, but as a double-vee, I guess I get it. (I’m tempted to call the Napier Lion a Ш12, but Sh-12 isn’t exactly catchy.)

What the hell are you getting at, I hear you ask.  I get that question a lot. The reason I bring up the Napier Lion is that it demonstrates, better than the Veyron’s W16, that you can take a pretty ordinary set of cylinders (banks of I4s) and turn them into bizarre, high-power variants. It was weird aircraft engines like the Lion that got me interested in weird engines to begin with. Unsurprisingly, someone took a pair of W12 Lions and put them in a car, breaking a land-speed record and becoming the first to break the 350 mph barrier. And trust me, it’s not the last time we’re going to see weird engines dropped in cars.

The Radial

(Wikipedia.)

For some reason, I think that looking at that animation while you had a really bad fever (or after eating funny mushrooms) would be really scary. But there’s not that much scary about it. It’s just a radial-5 engine, which proves that, there are more interesting ways to arrange pistons than lines and Vs.

I really like radial engines. There’s something pleasing about that five-fold symmetry. It’s like a starfish made of explosions. It also offers some serious advantages if you’re looking for an engine to stick in a propeller-driven airplane: compact and powerful, but with pistons still far enough apart that you can air-cool them, which eliminates the radiator, which is a notoriously brittle piece of hardware. And you don’t want brittle stuff on, say, a fighter plane.

For symmetry and smoothness, nearly all four-stroke radial engines have odd numbers of cylinders. A two-cylinder radial is just a two-cylinder boxer. I’ve seen videos of three-cylinder radials, but I like pentagons better than triangles, so I won’t bother with those. Plus, talking about five-cylinder radials gives me an excuse to show you a video of a Toyota being powered by an airplane engine. And this whole section has pretty much been an elaborate segue to talk about the Plymouth Air Radial Truck:

(From Motor Trend.)

Because, sometimes, you wake up in the morning and think “You don’t see enough nine-cylinder hot rods out there.” That is a 300 horsepower Jacobs 9-cylinder radial airplane motor from the 50s. There are plenty of things about hot rods that I don’t like (they’re always alarmingly low to the ground, for one, which bothers me for some reason), I will never deny that hot rodders are insanely creative in all the right ways. My proof? Look at that picture again.

Naturally, the radial engine lost a lot of its popularity when turboprop and turbojet engines became reliable and affordable for airplanes. It didn’t help that, eventually, engines like the I4 and F4 became refined enough and powerful enough to do the same job as a radial without needing the specialized radial construction.

But there was a period when the radial was king of the air. Within that period was a really wild period when planes needed more power than an ordinary radial could give them. Trouble is, if you want to make a radial engine with more than 11 cylinders, you have to make it really wide so that those cylinders can stick out to be air-cooled. And if you do that, then you’ve just stuck what amounts to a dinner plate on the front of your airplane, which is no good for aerodynamics. Engine manufacturers solved this with multi-bank radial engines.

The Wasp Major

(Bet you can’t guess the source.)

That is a cutaway of the Pratt and Whitney Wasp Major, which is a beast of a machine. It has 28 cylinders (four banks of seven cylinders) and a built-in supercharger. It has a displacement of 71 liters (compare that to the Bugatti Veyron or Dodge Viper, two high-power cars, both of which displace all of 8 liters.) It produced up to 3,500 horsepower in its original form, and over 4,000 once they added turbochargers. It also sounds pretty fucking awesome. If I was a millionaire and wanted to build a hot rod, I think this is the engine I’d put in it. Either this, or our next weird engine…

The Zvezda M503

(From Flickr, this time.)

I live in North Carolina. We’re one of the home states of NASCAR, which might be the ultimate in redneck racing. I went to a monster truck show last weekend, at which one of the events was lawnmower racing. That’s kinda what we do down here. We like big trucks, noisy cars, and bizarre racing. Tractor pulling is popular down here, too.

If you don’t know, tractor-pulling is an odd sport where you hook a tractor to a weighted sled and try to pull it a specified distance (usually 300 feet or 100 meters). On top of the sled is a sliding weight which is geared to the wheels so that it moves forward in proportion to the distance pulled, making the front of the sled dig into the dirt, making it harder to pull the farther you pull. Unsurprisingly, that takes a lot of power. I’ve seen pictures of tractors with as many as five or six supercharged V8s, tractors with 18-cylinder radial engines, tractors with two diesel V12s, and tractors with helicopter turboshaft engines.

I always assumed tractor pulling was exclusive to American rednecks. Clearly, I was ignorant, because a lot of the really good tractor-pulling videos are from Germany, the Netherlands, and Australia, where it’s apparently a really popular sport. And my favorite tractor by far is the German “Dragon Fire.” I don’t care if you don’t like big engines or tractor pulls. I insist you watch this video of Dragon Fire in action.

As much as I like big engines and weird engines, I’ll freely admit that tractor pulling seems a bit excessive. Five supercharged V8’s? Just looks silly to me. Like a truckload of engines collided with a truckload of bad Ikea chandeliers.

Dragon Fire, though, has a more elegant solution. Well, kind of. It depends how you define “elegant,” I guess. Dragon Fire isn’t powered by a bunch of V8s. It’s powered by a single 42-cylinder radial engine: the Zvezda M503, built for use in Soviet missile boats. The 503 has 42 cylinders (6 rows of 7). It weighs five times (almost five and a half times) as much as my car. It displaces 143 liters (which is about the volume of a bathtub, according to Wolfram Alpha). In its stock form, it produced nearly 4,000 horsepower. And it’s a diesel, too.

I should mention that the M503 powering Dragon Fire is running on methanol, not diesel fuel. And it, apparently, produces closer to 8,000 horsepower, which is absolutely ridiculous, and which makes me happy.

The Swashplate

(From the website of Douglas Self, who’s compiled a whole bunch of awesomely weird engines.)

I wouldn’t want to be the guy who proposed that design. I’m sure some stuffy executive looked at that, took out his monocle, took his cigar out of his mouth and said “Stop bringing me nonsense and bring me a real engine!” But the swashplate engine is real, and it’s pretty damn cool. It operates just about the same as any other piston engine, but instead of turning a crankshaft, the swashplate engine pushes on an eccentrically-mounted disk. Not only does this squeeze four (or more) pistons into a compact package, but it also eliminates the heavy crankshaft and provides a natural gear reduction. Apparently, while it has been used on a few cars, and was considered for use in airplanes, its main use is as the powerplant in torpedoes, where its small frontal area and corresponding tiny drag is vital.

For some reason, I really like the swashplate engine. It’s about as far as you can take a traditional fixed-cylinder design. It’s just delightfully weird, and it’s weird that it actually works. (Make it any weirder, and you’ll get awesome stuff like the Duke engine, which didn’t make the list because its cylinders aren’t fixed, and that was one of the arbitrary qualifications I came up with.)

I also like that the swashplate engine has been built in Lego form, by the awesome YouTuber DrDudeNL.

The Chrysler A57 Multibank

(Found via Jalopnik.)

When the United States entered World War 2 in 1941, apparently, Chrysler was tasked with producing a high-power engine for the M4 Sherman tank as quickly as possible. They delivered a 30-cylinder engine. 30 cylinders isn’t as many as 42, so the A57 shouldn’t be as impressive as the Zvezda M503. But it is, for my money. Because Chrysler did a clever thing to meet the deadline. To allow them to use existing engineering, they didn’t exactly build a 30-cylinder radial. They built a 30-cylinder engine made of five Chrysler I6 engines, attached to the main output shaft by gears. Here’s what that looked like:

(From Old Machine Press.)

Using five existing I6s saved Chrysler design time, and they already had the machinery set up to make I6s, so they didn’t have to retool any factories, presumably. The A57 really is just five straight-6 engines stuck together. That’s the kind of Mad Max/McGyver creativity I like. Sure, the engine only produced 450 horsepower, but it was surprisingly compact, and I love this kind of simple innovation.

Honorable Mentions

I wanted to include the Junkers Jumo 205, but I’m running long as it is, and I already talked about opposed-piston two-stroke engines when talking about the Napier Deltic. I wanted to include the Duke Engine, but it’s got rotating cylinders, which disqualified it. For the same reason, I didn’t talk about the weird rotary radials developed early in piston-engined flight. I didn’t include the Wankel rotary engine, because it has no pistons. I didn’t mention awesomely weird concepts like the nutating engine or the gerotor combustion engine for the same reason. Plus, there’s only so much time in the day, and I’ve taken up enough of yours. But if you’ve got any weird engines you think I should’ve included, leave them in the comments. I might stick then in an addendum later on.