AUTONEWS

This is what a car engine looks like without a timing belt or chain. Are they indestructible? We analyze it.

We live in a time when, above all, timing belts have become a major player, and not precisely for the purpose for which they were designed. Many users have found oil-immersed timing belts have caused major breakdowns in their cars, the most famous example being the Stellantis Group, although other brands have also used this solution at some point.

At the same time, the timing chains used in other engines also have the potential to fail, which can seriously dent your savings. While these parts alone cost between €50 and €200, depending on the model, the labor involved in repairing or replacing them in hours can mean the final bill can reach up to €3,000.

Given this situation, we wanted to review examples of engines that have been marketed without using either belts or chains. Specifically, they have been installed by brands such as Volkswagen, Ford, and Toyota. Instead, the camshafts were driven by the crankshaft through a set of gears. This, as is often the case, has a series of advantages and disadvantages, which we will review below.

This is what engines without a timing belt or chain look like...As our colleagues at Auto Motor und Sport explain, at first, doing away with the timing belt may seem like a great advantage. This rubber part actually contrasts slightly with the rest of the block, which is metallic. Its function is to precisely control the camshaft and valves at both low and high rpm. And for this task, a set of metal gears can do it better, hence its use in many Formula 1 cars and cars that participate in the 24 Hours of Le Mans.

As we mentioned on Autonews, in some modern engines, the timing belt passes through an oil bath, something that the rubber or plastic in this element doesn't like at all. This material is subjected to a corresponding amount of stress, which can cause serious engine damage, as has already been proven. Faced with this situation, many opted to use an iron timing chain, which offers advantages in terms of durability and precision. However, there are also examples of chain elongation or disintegration of the guide rails.

Considering these aspects, from a mechanical point of view, everything speaks in favor of using spur gears, which are usually helical on parallel shafts, so they can be designed with any imaginable ratio, right down to the camshafts. Beyond racing engines, it has also been used in large-displacement diesel engines that operate at low speeds.

Even all auxiliary units, such as the water or oil pumps, the compressor used by the air conditioning, or the power steering, could be driven by a common gear. However, modern engines, which are subject to strict emission regulations, now require that these components be decoupled from the engine while driving. This is intended to reduce fuel consumption, but increases production costs.

Advantages of engines with spur gear transmissions...What is clear is that spur gear drives are primarily found in gearboxes and rarely in engines. They offer both technical and economic advantages. Among the most important are their simple design and more robust construction, allowing them to enjoy a long service life. These components ensure very precise power transmission, which can have a positive effect on smooth operation.

Disadvantages of engines with spur gear transmissions...There are a number of other factors that make using spur gear drives impractical in certain situations. First, they produce a lot of noise, compared to a rubber timing belt. They can also cause annoying vibrations, especially at high speeds. And we must also keep in mind that the gears are not indestructible, as they are subjected to heavy loads on their flanks. Not to mention that changing them is complex and expensive. And the last detail is that they require a large space in front of the engine, given how tight their current situation is in this regard.

Examples of engines with spur gear transmissions...If you're curious to know the models that have used this type of system. One of the brands that used it was Volkswagen, specifically in the 2.5 TDI codenamed EA 153, which was sold between 2003 and 2009 for both the T5 and many Touaregs. This five-cylinder engine didn't have any major breakdown problems, and was considered a reliable engine.

Another example is Toyota. When the Japanese brand still had diesel engines in its range, it has been a long time since they were removed from its passenger cars, they used it. Specifically in the so-called B engines, with four cylinders and displacements between 3.0 and 4.1 liters. Added to this is Ford, which also experimented with this technology, but its gears weren't made of metal and broke over time.

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