What do you have humming under the bonnet of your car?
Most likely it’s a four-cylinder petrol or diesel powered internal combustion engine. Even the most non-conventional engine layouts are humdrum, even if it’s Subaru or Porsche’s flat-four (or six) boxer or Fiat’s inline twin. Engineers have tried all sorts of layouts and designs trying to distinguish their marque from others. Some weird designs came to fruition, either from chasing power or trying to improve efficiency.
The W-16 Bugatti
Possibly the most complex engine with a warranty ever created, Bugatti’s W-16 is the stuff of legend. The 8.0-liter, 1000-plus-hp W-16 is the most powerful and complex production engine in history. It has 64 valves, four turbochargers and grunt to spare - 922 lb-ft at 2200 rpm. Its W-shaped, 16-cylinder layout has never been used before and likely never will be again.
The Sleeve-Valve
Charles Yale Knight must have had a bad experience with traditional poppet valves. According to Knight, poppets were too complicated and the train of springs and followers too inefficient. He designed a sliding sleeve around the piston, driven by a geared shaft, which exposed intake and exhaust ports in the cylinder wall and called it a sleeve-valve. Sleeve-valve engines offered high volumetric efficiency, low noise and no springs assured there was no risk of valve float. However, it was complicated and had high oil consumption. It was patented in 1908, and subsequently appeared in everything from Mercedes-Benzes to Panhards and Peugeots. The sleeve-valve rolled out of favour when conventional valves became better able to cope with heat and high rpm.
The Wankel
Felix Wankel did not have it easy when it came to explaining how his design worked. It is not easy to explain how a front-loading washing machine with a convex triangle inside it runs better than a conventional piston engine . But not only does it run, but it’s also well balanced. The rotor is the triangle with convex faces and its three corners are called apexes. As the rotor spins within the housing, it creates three chambers that are responsible for the four phases of the power cycle: intake, compression, power, and exhaust, just like a piston engine, except that each face of the rotor is always at work on one stage of the cycle. This efficiency leads to high horsepower outputs relative to engine displacement, but the engine is notoriously thirsty. Ask any Mazda RX-8 owner.
The H16
Formula 1 also saw the advent of the weird BRM 3.0-liter, 32-valve H-16. In essence, it was two flat-eights, one on top of the other. More than 400 hp put it in the F1 ballpark but the H16 was handicapped by weight and reliability. Jim Clark, its only F1 win, was at the 1966 US Grand Prix. BRM also developed a more conventional supercharged 1.5-liter V-16. It spun to 12,000 rpm and produced roughly 485 hp. And that’s the most conventional engine in this lineup.
The A57 Radial
Five 251 cubic inch inline-sixes arranged radially around a central crankshaft. No, it wasn’t an aircraft engine. It powered the M4A4 Sherman tank. That makes it 30 cylinders and a total of 1255 cubic inches. It had, five carburetors and five distributors. Chrysler built the A57 using as many off-the-shelf components from the cars it built as possible. The 425-hp radial also powered the earlier M3A4 Lee battle tank.
The V16T Cizeta
A rare bird that still made it into limited (very limited) production. Like the Veyron’s W-16, the Cizeta’s (nee Cizeta-Moroder) engine is also a sixteen cylinder but it isn’t a true V engine. The 560-hp, 6.0-liter V-16 is a two flat-plane V-8s sharing a single block and joined by a central timing case. What makes it weird is that the engine is mounted transversely with a central shaft that feeds power into a rear-mounted transaxle.