7 Cylinder Production/Competition Cars?

"Redd, the RX-7 that could" (tacomatuesdays) 10/16/2013 at 03:23 • Filed to: None

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I'm reaching out to all those who dare to call themselves knowledgeable automotive enthusiasts. Has there ever been a 7 cylinder production car and/or racing car, and if so, what is your favorite?

Mikeado > Redd, the RX-7 that could 10/16/2013 at 04:26

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I've tried finding this out before. There are a few agricultural vehicles with 7-cylinder engines, and planes with radial 7cyl engines, but aside from Gordon Murray considering a V14 (two I7s, of course) for the McLaren F1, I'm pretty sure there has never been a 7-pot car engine. Odd numbers of cylinders aren't as smooth as even ones. If an inline-5 feels a bit rough then an I7 would be notably rougher, whereas a straight-six is perfectly balanced and very smooth, as well as easier to fit in to a car for being shorter.

Maybe someone could try a V7, but that would be slightly unbalanced from left to right.

GhostZ > Mikeado 10/16/2013 at 04:36

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Radial or inline would be the only way to do it, unless you made the engine with varying sized pistons and intakes, so the rotating assembly on the 3 left cylinders was the same weight as the 4 on the right, but even then, you're shaking the whole thing like a paint can.

McMike > Redd, the RX-7 that could 10/16/2013 at 07:55

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I love them. I just wish someone else besides Mazda would do it.

Niquemarshall > Redd, the RX-7 that could 10/16/2013 at 08:25

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Hmmm I would imagine that for a 7, the crank would be a bit too long/heavy, and won't be able to rev high with the crank literally bowing from being too long

vdub_nut: scooter snob > Redd, the RX-7 that could 10/16/2013 at 10:29

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Define "car"

The Continental R-670 , a 7-cylinder radial aero engine which first flew in 1931, became a widely used tank powerplant, being installed in the M1 Combat Car , M2 Light Tank , M3 Stuart , M3 Lee , LVT-2 Water Buffalo .

But that's as close as it gets.