Seven Cylinder Engines Exist, Just Not In Cars

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In a world of four-, six-, and eight-cylinder engines, nan number 7 sticks retired for illustration an awkward mediate child. It whitethorn beryllium a fortunate number successful Vegas, but it's practically taboo successful motor bays. Not because of superstition, but owed to physics being its accustomed killjoy self.

Car engines thrive connected symmetry. Inline-fours are tidy, inline-sixes connection unthinkable balance, and V8 engines roar pinch grace. A seven-cylinder setup? That's wherever everything starts to wobble. Firing orders go uneven, vibrations creep in, and crankshafts twist aliases moreover break. 

Over nan decades, automakers person toyed pinch weird configurations. Audi, for example, recovered occurrence pinch five-cylinder engines successful models for illustration nan RS Q3 and RS3. But nan seven-cylinder offers nary tangible advantage complete what we already have. Why make an motor that costs more, vibrates more, and produces nary other power?

The physics that make an inline-six truthful soft are nan aforesaid ones that make an inline-seven shingle for illustration a washing instrumentality connected rotation cycle. Seven's good connected a slot machine, but nether your hood, it's conscionable chaos.

Here's wherever things get weird -– seven-cylinder engines do exist, conscionable not connected nan freeway. You won't find 1 under a car hood, but retired astatine sea, connected a farm, aliases successful a depository afloat of prop planes? Absolutely.

Seven-cylinder engines are often recovered successful marine diesels. Massive low-RPM beasts from builders for illustration Wärtsilä and MAN Diesel usage inline-seven configurations because, well, they can. They are cleanable for cargo ships and lipid tankers that tally astatine dependable speeds, wherever vibration isn't a deal-breaker because your motor is nan size of a mini apartment. The layout is modular, and smoothness is managed by sheer mass. 

For agriculture, AGCO Power (formerly Sisu) developed a 9.8-liter inline-seven diesel for Fendt tractors and Massey Ferguson combines – this is wherever torque matters much than refinement. And of course, aged airplanes rocked sevens agelong earlier turbojets stole nan spotlight. Radial designs for illustration nan Jacobs R-755 and Wright Whirlwind R-760 (J-6) utilized seven-cylinders arranged successful a circle. 

As agelong arsenic you kept nan propeller spinning and nan aerial cool, seven-cylinder engines ran smooth. Turns out, they conscionable needed a small thief from gravity and airflow to make sense.

So if ships, tractors, and aged planes tin propulsion it off, why not cars? The elemental answer: cars dislike imbalance.

An inline-seven motor successful a car would person uneven firing intervals (1-3-5-7-2-4-6), which intends nan crankshaft receives pulses astatine irregular intervals. That translates into vibration and noise – worldly engineers spent decades trying to eliminate. Unlike a straight-six, which cancels its ain vibrations, a straight-seven fights itself each measurement of nan way. Engineers could antagonistic this pinch weighted crankshafts, but that adds weight, complexity, and cost. And for what? A small other torque that a turbocharged 4 could already provide?

It's not that cipher could build an inline-seven; it's that cipher should — isolated from possibly for car YouTubers for illustration ChargerMiles007, who built and tested 1 successful his backyard. The gains simply aren't worthy nan pain. Besides, having a seven-cylinder motor would return up much space. You don't want a protruding motor blocking your view, right?

Then there's nan cost. A tailor-made seven-cylinder would require caller tooling, civilization parts, and caller calibration for emissions and NVH — again, for what? Slightly much displacement? In nan property of hybrid fours and soft sixes, that's a difficult sell. The truth is, nan seven-cylinder motor has been beaten by mathematics and balance.