- Straight-six, V6, inline-six? Slant-Six? Six-cylinder engines! (quirky brief jingle) - Thanks for tuning in.
Before we talk about these Donegal engines, click
the subscribe button! Means a lot and that's what helps us continue to try to make new shows! Alright. Today we're talking about inline-6 cylinder engines
and the V6 engine. Is one superior to the other? The answer's the same as if you ask me what kind of underwear I
prefer, boxers or briefs. And I'll just tell ya, Depends. (cackling) First off, there's the inline-six engine. Dutch manufacturer,
Spiker, built the first one for their all-wheel drive
Spyker 60 horsepower race car in 1903. Sometimes we call em straight-sixes. Or when referencing old Chryslers, they're known as Slant-Sixes cause they're installed
at a 30 degree angle. Today, the Nissan RB,
(engine revving) Toyota 2JZ
(engine revving) and BMW S54 engines
(engine revving) are the best known inline-sixes around. But why are they such a big deal?
- Yeah! - Hang on and I'll get to it. For one, having all the cylinders in a row makes an inline-six inherently balanced. In a piston engine, there's
a lot of moving parts. We know this. The pistons move up and down and they have inertia. And every time they change direction they exert what are called primary forces. That translates into engine vibration. Primary means that these forces happen only once per revolution of the crankshaft. Secondary forces are also related to the pistons' up and down movement. But they're just a little bit different because of where they're exerted. If the piston starts at top dead center, then the first 90 degrees
of crankshaft rotation the piston travels a little bit further than half way through its whole stroke. That's because of the
way the connecting rod attaches the piston to the crank. From 90 to 270 degrees of crank rotation, the piston doesn't travel quite as far. Then, from 270 to 360 degrees, it goes a bit further again. Since each portion of the movement happens in the same amount of time, that means the piston is
traveling a little faster in the top half of its stroke than in the bottom half. These different speeds are the secondary forces that cause an imbalance of the engine which means more vibration. Well an inline-six operates like two inline three-cylinder engines placed end to end. The pistons move as mirror image parts. With one and six, two and
five, and three and four always moving in tandem. When one pair is at top dead center, a second pair is moving downward, and the third pair is moving upward. That cancels out the primary forces. Then, each of the crank throws is separated by 120 degrees which cancels out the secondary forces. The result is that the engine
naturally runs smoothly. Oh, and uh, it sounds pretty good too. (car engine revving) Another advantage to a straight-six is that putting all
the cylinders in a line is a really simple layout. It only needs one basic engine block, one cylinder head, one valve cover, and one set of valvetrain components. Since it's naturally balanced, there's no need to add balance shafts or anything extra to smooth it out. That makes it both a
little cheaper to produce and much easier to work on. Straight-Sixes are long and tall engines which can be both good and bad. A car's gonna need a pretty long nose to accommodate the engine. Not a bad thing if you're building a pretty good-looking sports car. Or if you're singing the Humpty Dance. ♪ The The Humpty Dance is
your chance to do the hump ♪ This shape also leaves
a lot of extra space along the sides of the engine bay for performance enhancers like turbos and exhaust headers. On the other hand, the long vertical shape of an inline-six means it's got a slightly
higher center of gravity than a V-shaped engine and a bigger, longer crankshaft
and camshafts are gonna try to flex more than shorter ones would. But there've been so many advancements in modern engine technology that that stuff really doesn't
matter too much anymore. That length also means that it's also almost
impossible to use a straight-six in a front-wheel drive car. (high rev engine motor) When a straight-six
engine's turned sideways there's almost no room left to connect the transmission in the front axle. That's why most front-wheel drive cars have more compact inline-fours or V6s. On top of that, most manufacturers are in the business of
maximizing their profit so they do cost saving things like sharing engines across multiple platforms. The engineering effort required
to adapt a straight-six into an existing chassis or develop something completely new just for one especially cool engine? It doesn't fit on that old bottom line. The fact that the inline-six is so silky smooth and is a less common engine, it makes it even more appealing. (engine revs)
(tires screech) Alright next up let's talk about the more common V6 engine. A V-layout is more complex
than an inline engine. And a V6 didn't really
appear in mass production till the Lancia Aurelia in 1950. A V6 is basically two inline three-cylinder engines sharing a crankshaft, and placed at an angle from each other. Usually 60 or 90 degrees. In this configuration the primary and secondary forces that cause engine vibrations don't all cancel each other out. So V-shaped engines tend to run a little rougher. To make a V6 run smoothly counterweights are needed to balance the unwanted inertia and reduce vibration. Weight is added to the crankshaft to counteract primary forces, and balance shafts are sometimes needed to counteract secondary forces. Plus, the larger the
engine displacement gets, the more counterweight it'll need. This adds more complexity to the development and production of V6 engines. Because the two banks of cylinders aren't laid end to end, a V-shaped engine can be way shorter than an inline. Heck, a V6 can be shorter
than an inline-four. That makes it easy to package in almost any car. And it works well for the transverse front-wheel drive platforms that are so popular in modern cars. It also means it won't cost
manufacturers much extra money to offer a punchier V6 option in addition to the typically lower power but similar length four bangers. Here in America where
people herald the phrase, "There's no replacement for displacement", V-shaped engines
(engine revs) really took off in popularity because you could squeeze in the extra cylinders making extra displacement while taking up much
less longitudinal space. However, the wider V shape of the engine leaves less room along the sides for turbos and things like that. But that doesn't stop manufacturers
from doing it, though. The Nissan GTR and the new Acura NSX are notable examples of
sweet turbocharged V6s. But they're more tightly packed
deep down in the engine bay. And that makes working on them even more of a headache. Oh, and another thing
that makes maintenance a bigger headache on a V-shaped engine is that there's gotta be a set of stuff for two banks of cylinders,
instead of just one. That's two sets of camshafts, two cam sprockets, two valve covers, two cylinder heads, and two exhaust headers. It also needs a much longer timing belt or timing chain. So that's more stuff to manufacture and more stuff to deal with in terms of maintenance. Still, the V's shorter length makes it so much easier to transplant into multiple car platforms while maximizing interior space, that it's by far the most popular six-cylinder option today. That doesn't mean the
inline-six is dead, though. In fact, Mercedes is actually replacing its V6 engines with a new turbo-charged three-liter straight-six. With efficient inline-four
cylinders starting to become the base engine of choice, well, moving to a closely related, inline-six makes sense from
a production standpoint. So, just like my favorite
movie, The Longest Yard, each engine has pros and cons. Ultimately it comes down to preference and what you're planning
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