Why are there NO AUTOMOTIVE INLINE-7's? #shorts

A straight-7 is a very unique layout, possibly the largest odd number inline engine to be produced. There are several reasons why these engines are so incredibly rare. Most of those existing are large two-stroke marine power plants and only a single off-road one found its way out of a factory as a production engine: AGCO Power Sisu 9.8-liter.

There were no straight seven-cylinder engines ever made for a road car. The main reason is cost as it is difficult to engineer and balance out. Each four-stroke engine fires a cylinder after 720° of a crankshaft revolution which equals a power stroke each 240° for a 3-cylinder or 144° for a 5-cylinder. However, the 7-cylinder is different and 720°/7 equals 102.857142857rep... a repeating decimal.

It is also a very long engine besides issues with a torsional vibration of the long crankshaft. Yes, some longer inline-8's existed when the majority died in the 1950's, but a straight-8 is easier to calculate and balance out. I myself wonder what such a gasoline race car engine would sound like...

- Vlog -

- Support -
XHV: hvs1HU2yCqNFBJHCvkQk67Beo5XaiXNHb5SVkPTL1whyLhbwTdVmG1z4GProuUqVwpj5KWMU3Y3MMHSLjiYSFVka1Skr29nZPU
XMR: 4294E5emhNXVhM1odiiwLFQTq6xcK7y6Z3WYt3fEUan9UqnUTvNX23tGzdgkgksx4n23na1o2rRzS4L6xLQ6RopF6q1MLAd

- Disclaimer -
This video is fair use under U.S. copyright law because it is transformative in nature, uses no more of the original than necessary and has no negative effect on the market for the original work.

- Credits -
“SISU Diesel Engine Rotation” by Kelly Last

“Starting 25000KW Power 7 Cylinder Marine Diesel Engine 2 Stroke (HEADPHONES)” by marinersgalaxy

“ME MAN B&W 7S 50MC-C” by Ivan Klimchenko

“I7 Inline 7 engine firing order (AGCO POWER/SISU HD 98) AudioVisual demonstration 1 2 4 6 7 5 3” by William Moser

“Hudson 8 Startup” by nervecenter100

“Kawasaki Triple (?) Seven cylinder running bike” by Rick Brett

“AGCO developing 7-cylinder, 12-cylinder engines” by PentonMediaAg

[Mr.Marbles]

VR 7 would be cool tho. Wonder what it would sound like. Like a mixture of a 4 and 3 pot or like a 5 cylinder but smoother?

[Jay_Speed]

40 years ago I visited a company in France that had a straight-7 diesel for power generators and a very narrow V7 petrol for marine based, navy and so on. They still existed in the eighties but than had only V8 to V16 engines, for the same applications. Very expensive units they made. I forgot the name of the company, but they where based in the south of France.

[peterpimmelmann]

id love to hear that agco inline 7 run, sadly there is very little info online.

[FliesFLL]

1. Weight. A V8 of the same displacement will be lighter.

2. Lack of RPM capability. The long crankshaft would have to be very heavy and strong to resist failure due to torsional vibration.

Great video!

[theblackbear]

It should be noted that most (if not all) Marine in-line 7's are 2 strokes -thus its 7/360 vs 7/720, plus they are low speed engines so balancing considerations are a little different.

[Greenwithao]

Someone should make a Inline 7 just to flex on people with a straight 6. Sure you could get 8, 10, or 12 cylinder but there is something about just one upping that is the ultimate flex.

[Waanie]

Somebody should build a 3.5 litre 7 cylinder engine just to let us hear what it would sound like.

[haweater]

Several years ago I owned a John Deere tractor with a inline 5 cylinder diesel. The same engine was used in a few models of skid steer loaders.

[scottearl]

My buddy had a v7 for a while sounded mean till he put the sparkplug back in😂

[backyardrestorations]

I always wondered this. Very interesting.

[tgc_-_]

That is easy to make a Inline 7 engine. For vehicles.

[jimbenson]

I worked on a fishing boat some time last century. It had two main engines, each one had two straight nine cylinders bolted together with two turbo chargers, I think max rpm was 900rpm.

[ridezosmon]

Simpler answer: "Too expensive and not very profitable to develop."

[mrdanforth]

If you want an engine that is smooth and fires evenly it must be some multiple of 2 or 3 cylinders. 4 cylinder engines have good primary balance but a secondary vibration. A straight six has the smallest number of cylinders having perfect primary and secondary balance, and overlapping power impulses. This makes it inherently smooth which is why so many luxury cars used the "big six" concept for so long.
A straight eight, or V8 is just as smooth or smoother if it has crankshaft throws at 90 degrees.
There have even been experimental straight nine cylinder engines built, they were extremely smooth but did not offer much advantage over a straight eight, and the makers feared sales resistance until they could educate their customers so they never made them for sale.
There have been a few inline 5 cylinder engines. They were all adaptations of a 4 cylinder, where a larger engine was wanted but there was not enough room for a straight six and they did not want to spend the money to develop a whole new V6. Somehow they made them work although the layout is not ideal.
The only other cars with odd numbers of cylinders, are a few 3 cylinder economy cars. They had some of the smoothness (balance) of a six but really, you might as well make a 4 unless you have some special reason, like a 2 stroke, or wanting a smaller adaptation of a 4.
Other than that, the only engines with odd numbers of cylinders made in large numbers are radial aircraft engines.

[WilliamMoser]

I was wondering when I would make it into one of your vids, thanks for the credit in the description! :)

[fsu]

I have an in-line 6 in my Chevy trailblazer and it’s my favorite engine by far

[-Eckhart]

What you do is combine a normal 4-cylinder (with normal 180° firing intervals) with a normal 3- cylinder thus: the "four-cylinder" at cyl. Nr's 1, 3, 5 and 7; the "three-cylinder" interspaced at cyl's 2, 4 and 6. This means the engine has a dominant four-cyl. balance from the point of view of the crankshaft. Clearly the firing strokes are now overall out of phase in the manner of a 90° Vee 6, giving it the same hoarse, raspy exhaust note. I think that's what we wanted.

[lonedri]

i would love to hear a 7cyl tho, i5 and vr5 sound sound good, i wonder if it would be similar in some way

[_..-.._..-.._]

Just make it odd-fire or semi-odd where 4 cyls are evenly spaced and 3 are spaced evenly but off-phase from the other 4

[mariodouradoo]

Yes, there are 7 cyl. In line engines. They exist in ship industry at least. They are 2 and 4 strokes as well.