The differences between V engines, Inline engines, and Flat engines


Why hello there, I assume that because you are here that you either A) hit this post by mistake or B) Want to know a little bit about the differences between three engine layouts. Whether you are here on purpose or not, here is a little background. V engines sit anywhere from 60 degrees to 90 degrees, they have their pistons shaped, you guessed it, in a “V” shape. Pistons in an inline engine sit…inline, meaning that they follow one another in a single plane. H engines (or flat) sit 180 degrees to each other. So with that out of the way, lets get on with it

One of the more common engine layouts, the V format is used for just about everything above 5 cylinders (except for the Lancia Fulvia’s V4, but that’s for another day). Sitting anywhere from 60-90 degrees, these engines can be smoother than their inline counterparts (not always though i.e. V6s) and can be more practical to use than a flat engine (as V engines can be mounted transversely easier). Typically found in 6, 8, 10, 12, and in super rare, only when the stars align, on the night of a blue moon, 16 cylinders. Not just that, but a V engine can make more torque at a lower rpm thanks to the fact that it has two pistons firing on each side (source).

Advantages: Can be mounted transversely or longitudinally with relative ease compared to inline and flat engines, can make more torque, shorter than an inline engine

Disadvantages: Cost can go up because it needs double the parts that an inline engine needs, taller than a flat engine

Verdict: Arguably the best setup out there

Inline engines

Found in 3, 4, 5, and 6 cylinder forms, the inline engine is starting to gain populartiy (specifically in 4 cylinder form). With the smaller 3 and 4 cylinders being able to be mounted transversally, making them ideal for compact cars, and 5 and 6 cylinders being naturally balanced and smooth. Even though it can be a hassle to mount the larger 6 cylinders sideways, it can be done, as Volvo did with the pre-facelift S60 and V60 Polestar (which is now powered by a twincharged 4 pot). One company that is obnoxiously famous for it’s inline engines, specifically it’s 6 cylinders, is BMW. In fact, over the last 20 years, there has been 10 different straight sixes ranging from the 2.0L M50 to the 3.2L S52 (used in the E34 BMW 5 series and E46 M3, respectively.). Now, the 3.0L twin turbo I6 (dubbed the S55, or N55 in the M2, which is single turbo) is used in every M3, M4, M4 convertible, M3 competition pack, M4 competition pack, M4 convertible competition pack, M3 CS, M4 CS, and M4 GTS. It makes anywhere from 365 HP to almost 500 (depending on model and tune, of course). Now let’s move on to the 5 pot. Ah yes, the V10 chopped in half. Not too many cars use this engine layout (as CT explained). Despite this, the main manufacturer of the 5 cylinder would probably be Audi, then followed super closely by Volvo (if this turns out to be flipped let me know so I can fix it). Like the straight six, the five cylinder is smooth (check CT’s video for more info). Not just that, but because it’s not used hardly at all, it gives the car a uniqueness to it, something that most people can relate (if they have driven a 5 pot car before). Moving on to the 4 cylinder: i.e. the McDonalds of the engine world. The 4 cylinder isn’t a bad thing, make no mistake, however, it’s used soooooo often that it just lacks something. To prove that 4s are used too often (mostly because fuel economy and emissions as well as power can be balanced easier), here is a list of all the hot hatches/sedans/coupes (note that these are the ones that can be had for around $50,000 USD) currently using a 4 cylinder

Honda Civic Type R

Ford Focus RS

Honda Civic Si

Ford Focus ST

Subaru WRX STI


VW Golf R

Hyundai i30N

Ford Mustang

Chevy Camaro

Audi S3

Fiat 124

Fiat 500 Abarth

Mini Cooper JCW

Ford Fiesta ST

You can see where I’m going with this. 4 pots are stupidly common, and while they aren’t all bad, they aren’t all good either. As for 3 pots, I’m not going to jump too in depth because they are so uncommon that it would be a waste of everyone’s time (I think only Ford sells them).

Pros: Smoother than V engines, less complex with less moving parts

Cons: Longer and taller than V engines, harder to mount bigger engines transversely or longitudinally without major mods going in to make it fit. Some are too common for my personal taste

Verdict: It’s like a pre-school soccer game, everybody wins!

Flat engines (H)

Last, we have the flat (or as I’m going to call it for this blogpost: H engines) engine. In this layout, the pistons lye on their sides, 180 degrees from each other, rather than in a straight line or at a 45-90 degree angle. This allows the H engine to be more balanced than a V engine because it sits so low, it’s not high enough to make it vibrate enough to cause any major shaking or unbalancedness in throughout the engine. As of right now, the only two companies that make and sell H engines are Subaru and Porsche. Subaru with their 2.5L and 3.6L H4 and H6, and Porsche with their twin turbo and N/A H6. While the inline and V engines take up more space, thus increasing the center of gravity which could effect handling, the H engine is wider than it is low, which means it’s lower to the ground, lowering the center of gravity (which you can see below)

I would go on more, but there’s not a whole lot to say, but there is someone who found more to say and you can check that out here.

Pros: According to an article done by Engineering explained, it says “Primary and secondary forces are well balanced. This allows for less weight on the crankshaft, resulting in less power lost to rotational inertia.” Not just that, but because H engines are so low, the handling of the car can change completley.

Cons: Wider than a comparable inline or V engine, fixing it can be an issue due to the fact that the heads are basically in the sides of the car

Verdict: A good idea, and a decent execution

In conclusion

All three layouts are great, with each having it’s own set of good and bad. The V engine will probably live for a little bit longer (mostly in V6 form), but even then, it will probably get replaced by the inline engine. The inline engine is probably the best here, seeing as there are so many varieties and ways to mount them, giving the makers more wiggle room than a V or H engine. Lastly there is the H engine. Not popular by any chance, but makers are still sticking with it, and hopefully they’ll stick with it for a bit longer. H engines are so uncommon now, the ones that are in production unique in the fact that they are the only ones (so please Subaru and Porsche, keep them in production).

Which one would I take? That’s a tough one for me because I love all three, but what I would take is a VR engine (plot twist intensifies) which is basically the love child of a V6 and I6. But that’s for another time. But out of those three I would have the inline engine because it can be a lot higher revving (A V6 is no match for a straight six) and it’s more compact than a V engine, and even though it’s one of the most common setups out there, there’s a good reason why, and that reason shouldn’t be too hard to see.