The Misunderstood Inline 5 Cylinder Engines

Engineers have experimented with inline five-cylinder engines ever since the 1930s. However, a straight-five engine was never fully developed until Mercedes Benz introduced the OM617, one of the most reliable engines ever. Since then, most automakers have either steered far away from the inline 5, while others, such as Audi and Volvo, have sworn by it.

The five-cylinder engine has brought a lot of success to those who took the time and effort to work out all the kinks. Ford Focus Mk2 is considered to be one of the most excellent FWD performance cars ever produced, for example. Audi TT RS, a performance upgrade from Audi TT, is well known and loved by car enthusiasts everywhere.

With such vast popularity and fandom that inline five-cylinder engines have gained over the years, we have to ask why most auto manufacturers won’t even consider the straight-five. Let’s pop the hood and take an in-depth look!

Engineering Behind The 5 Cylinder Engine

The firing interval of a five-cylinder engine is 144; A power stroke happens every 144 degrees, which means that between each power stroke, there are 36 degrees of overlap. The overlap between power strokes results in smoother power delivery. For comparison, the firing interval of a four-cylinder engine is 180, which means that there will always be a power stroke occurring with no overlap.

Now, if we do the math, we’ll understand that the firing order of a 5 cylinder engine is 1-2-4-5-3. Surprisingly, the firing order will balance out the engine vertically; In other words, the engine will be stable on a vertical plane.

The problem occurs on the horizontal plane; The firing order of a five-cylinder engine, which goes from one side to the other, will rock the engine back and forth. To counter the imbalance of an inline 5 engine, an additional balancing shaft must be put in for support.

The Pros and Cons of Inline 5 Cylinder Engines

Straight-five engines are becoming increasingly rare in production, due to cost and effort. However, this engine configuration brings with itself many advantages and only a couple of disadvantages. After all, Volkswagen wanted Golf R to come with Audi’s Inline 5 for a reason.

– The most significant advantage of Inline 5 engines is that they offer a smooth power delivery compared to an Inline 4. This is due to the straight-fives 36 degrees of overlap, as well as the vertical balance of the engine.

– Inline five-cylinder engines sound like a toned-down version of a V10. While musicians play instruments to create music, car guys rev their engines. Needless to say that every car enthusiast loves the sound of a straight-five.

– Front-wheel-drive vehicles have a hard time with engine placement inside manufacturers’ compact cars. Inline 5s fit seamlessly into smaller vehicles, as they’re more narrow than V6 engines and shorter than Inline 6 engines.

– Arguably, the only disadvantage of the inline 5 cylinder engines would be the plane imbalance. With 4 cylinder engines, the outer pistons move with each other, and the inner pistons move with each other. Due to the nature of straight-fives, a balancing shaft must be mounted onto the engine.

Cars That Makes Use of The 5 Cylinder Engine

Automakers prefer even-numbered engines, inline 4s, inline 6s, v6s, etc. due to the cost and effort required to engineer a well balanced straight-five engine. However, even today, five-cylinder engines still have a place on the auto market. Here are the best cars with an Inline 5.

Mercedes Benz 300D

Mercedes Benz 300D is the pioneer of five-cylinder engines. The Benz 240D 3.0, better known as 300D, made use of the indestructible OM617 engine. The OM617 proved so reliable that Mercedes continued production for 17 years! Although the diesel 3.0 liter OM617 delivered only 80 horsepower, the Mercedes Benz 300D more than made up for it with a stylish look and unmatched reliability.

Audi TT RS

Audi TT RS was a high-performance version of the Audi TT. With 394 horsepower under the hood, from the 2.5-liter turbocharged inline-five engine, Audi TT RS can achieve 0-60mph in under 4 seconds. The performance wasn’t the only thing that set the Audi TT RS apart from the crowd, though; The raspy sound, resembling a “baby” V10, was the music to every car enthusiast ears.

Ford Focus RS Mk2

Mark 2 Ford Focus RS was produced from 2005 to 2010, and even today, this Europe-only beast is considered to be one of the most exceptional FWD vehicles ever. The Focus RS Mk2 came with a 2.5-liter Duratec inline-five engine that was augmented to withstand 20 psi of boost, resulting in 296 horsepower. With its compact design, and the astonishing Duratec inline 5, The Ford Focus RS Mk2 accelerates to 60mph in under 6 seconds.

Summary

Automakers must sell a certain number of vehicles in order to profit, and in today’s highly competitive automotive market, that’s not easy to accomplish. Covering the expenses of developing an inline five-cylinder engine would cut into auto manufacturers’ earnings.

The inline five-cylinder engines have brought success to those automakers that were willing to take the risk; However, the demand for such an engine isn’t high. The straight-five offers more displacement than a straight-four, and it’s more compact than a straight-six or a v6. No matter how much we love the purring Inline fives, there is only a small portion of the market for such a narrow use.

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