Why Isn’t There A 7-Cylinder Engine?

Thoughts on the sound of the inline-seven? 🤔Thanks to Bespoke Post for sponsoring today's video – New Bespoke Post subscribers get 20% off their first box of awesome — go to bespokepost.com/drivetribe20 and enter code DRIVETRIBE20 at checkout

More educational content please, Mike has a great way of explaining it while posing a genuinely interesting question.

In radial engines odd numbers are generally preferred because then on the opposite side of a cylinder (a weakspot in the block) will be a particularly strong spot where the walls of two cylinders come together. And radials with even cylinder numbers, like 14 or 28 cylinders, often tend to be built like multiple odd-numbered radial "discs" behind each other

When you're talking about Sisu Diesel engines you're incorrect. The engines they build are 3, 4, 6 and 7 cylinder engines with displacements of 3,3L for 3 cylinder engines, 4,4L/4,9L for 4 cylinder engines, 6,6L/7,4L/8,4L for 6 cylinder engines and 9,8L for 7 cylinder engines respectively. And every single one of those is turbo charged. They are indeed modular in the sense that they only use 3 and 4 cylinder heads which they then combine to make 6 or 7 cylinder engines. The new engine family they just launched is quite different though and they have a V12 engine that's no longer manufactured.

The inline 7 cylinder that he was talking about at the end was the 98AWF by Agco. It's used in grain combines.

One thing you forgot to mention with those massive ship engines is that they have a number of markings on the power setting lever. Some of those are more critical than others, but they all have one thing in common: you can run the engine(s) at that setting for only a very short time, as the vibrations will tear the engine apart and generally speaking it's better not to run the engine at those settings at all. You can actually feel it when a ferry ship is docking and at times during the docking procedure the engine(s) run(s) momentarily on one of those power settings, as the whole ferry starts to vibrate. You can imagine the severity of the vibrations needed to vibrate an entire ship.

I love the educational type of content, would like to see more of it. I'm not really into the insane physics calculations and don't expect to see a 45 minute lecture calculating forces, but showing a quick final formula that is used like the one to calculate engine overlap is very nice.

I built and ran a FrankenBriggs 7 cylinder gasoline engine about 5 years ago (vids on my channel) It is made of individual single cylinder engine blocks with the cranks fastened together, and using a common ignition distributor and 2 carburators. It does indeed have its own unique sound, and ran very well. Cheers.

There were also straight 8's. Buick and Packard were known for their straight8's.

Also note that even though the straight 6 has its cylinders moving as pairs, they are not firing as pairs. A cylinder fires every 720 degrees of crankshaft rotation. Each member of a pair is 360 degrees out of phase with the other, which means you get six individual firings instead of three pairs. It's not just a doubled inline 3.

I was expecting this to be a long intro to why you are making a 7 cylinder car.

Been wondering this for years now, always trust drive tribe to answer my dumb questions 😂

Don't forget that the radial engines almost require an odd number of cylinders per bank in order for the firing order to work out in a simple way that's relatively easy to drive mechanically. They fire every other cylinder, and going around the whole engine twice will wind up firing every cylinder as long as it's an odd number.

Really like how this was explained clearly. Love the sound of my 5cyl, even if it is a diesel

8:37 I would only like to correct on one thing, super chargers and turbo chargers have been around just as long as adding more cylinders. 1905 for turbo chargers, and 1848 for super chargers forced induction has been around just as long as the internal combustion engine.

I wonder if a VR7 would work any better? Still fairly pointless but it would sort the long crankshaft issue

This is a really well made video explaining this topic. Tbh I think a lot of people that have nerded out on exotic engine designs have thought about the idea of a 7 cylinder.

There are plenty of straight seven and straight nine Diesel engines out there. French manufacturers like Duvant and Japy made a lot of them for example. Deutz also makes inline 7 and V14 engines.

2 of the best/reliable engines I've owned were both inline 6's

Having owned cars with both straight 5 and 6 engines, I found this fascinating. The straight six that I had was in a 2ltr Triumph Vitesse. That was a great car for a 21 year old to own! Sad to see it go, especially now, after so many years.