Sofia Martinez
Plastic timing chain tensioners are components in automotive engines that help to maintain the tension in the timing chain, preventing it from flopping or fluttering. They are made from highly engineered resins and structural fibers, designed to withstand high temperatures, forces inside the engine, engine oil, and harmful vapors. While some may refer to these tensioners as simply plastic, this term undermines the advanced engineering of the materials used. These plastic tensioners are favored over metal alternatives due to their ability to dampen noise transmission from the engine to the vehicle. They also require a shorter range of adjustment compared to sprockets, as they can deflect more of the chain's slack. However, plastic tensioners are not without their drawbacks, as they can fail and cause other engine problems.
| Characteristics | Values |
|---|---|
| Composition | Highly engineered resins and structural fibers |
| Purpose | Dampens chain harmonics, prevents whiplash, and keeps the chain in tension |
| Benefits | Requires shorter range of adjustment than a sprocket, quieter than metal, designed to withstand high temperatures, forces inside the engine, engine oil, and harmful vapors |
| Drawbacks | Susceptible to premature aging due to old oil, can fail and cause engine problems |
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What You'll Learn
Plastic tensioners are used to keep the chain from fluttering
While the term "plastic" may not be entirely accurate, timing chain tensioners made from highly engineered resins and structural fibres are commonly used in engines and bicycles. These materials are designed to withstand high temperatures, forces inside the engine, engine oil, and harmful vapours created by blow-by within the combustion chamber. They are also engineered to endure thousands of heat cycles without the need for lubrication.
In engines, timing chain tensioners are crucial for maintaining system stability and accurate timing. The majority of these tensioners use oil pressure to take up slack in the chain. However, old oil can cause premature ageing as it degrades the seals and clogs the oil passages. This can lead to timing chain stretch, which is not the stretching of the chain itself, but rather an elongation caused by wear to the chain's components.
In bicycles, plastic tensioners are used to adjust the tension on the chain to accommodate different chainring sizes. For example, the Brompton tensioner is a popular option, but some users have reported issues with its reliability and accommodating fluctuations in chain tension.
Overall, plastic tensioners play a vital role in keeping the chain from fluttering by maintaining the correct tension through their durable and heat-resistant properties.
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They are made from highly engineered resins and structural fibres
While some timing chain guides are referred to as "plastic", this is not entirely accurate. They are, in fact, made from highly engineered resins and structural fibres. These materials are designed to withstand the high temperatures and forces inside the engine, as well as engine oil and harmful vapours created by blowby inside the combustion chamber. They can also endure thousands of heat cycles without failing.
The use of plastics in timing systems, such as the chain tensioner, is becoming more common as automotive engineers strive to meet demands for lower weights, costs, and noise. For example, the Porsche Cayenne SUV uses a two-part tensioner made from two grades of Stanyl from DSM Engineering Plastics. The top layer, made from Stanyl TW314, a PA46 with good wear characteristics and oil resistance, comes into contact with the timing chain. Its non-abrasive nature reduces friction and prolongs the life of the chain. The base of the tensioner is made from Stanyl TW241f10, a 50% glass-filled PA46 that provides strength and resists oil, fatigue, and high temperatures.
Other plastics, such as HDPE, have been considered for use in timing chain tensioners, but their suitability is questionable due to their potential degradation by oil-based products. Nylon, on the other hand, is commonly used in chain guides, often with solid lubricants embedded to reduce friction and wear.
The choice of materials for timing chain tensioners and guides is critical to the performance and longevity of the engine. While plastics offer advantages in terms of weight, cost, and noise reduction, certain types of plastics may not be suitable for the demanding environment of the engine. Therefore, highly engineered resins and structural fibres are specifically formulated to withstand the unique challenges of this application.
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They are designed to withstand high temperatures, engine oil, and harmful vapours
While some timing chain guides are referred to as "plastic", they are actually made of highly engineered resins and structural fibres. These materials are designed to withstand high temperatures, engine oil, and harmful vapours created by blowby inside the combustion chamber. They are also built to endure thousands of heat cycles.
Timing chain guides are designed to keep the chain in tension, preventing it from fluttering when the engine speed changes. They are often the best indicators of the health of the timing chain, sprockets, and the entire engine. Abnormal wear patterns on the guides can indicate a problem with the chain system or improper tensioner and oil pressure operation.
The use of plastic in timing chain tensioners offers several advantages, including reduced weight, cost, and noise. For example, the Porsche Cayenne SUV employs a two-part tensioner made from two grades of Stanyl, an engineering plastic from DSM. The top layer, made of Stanyl TW314, resists wear and oil, and can withstand engine temperatures of up to 140°C. Its non-abrasive properties reduce friction and prolong chain life. The base of the tensioner is made from Stanyl TW241f10, which is 50% glass-filled PA46, providing strength, oil and fatigue resistance, high modulus and stiffness, and low creep at elevated temperatures.
However, the use of plastic in timing chain tensioners is not without its challenges. Some vehicle owners have expressed concerns about the durability of plastic components, noting that timing chain issues are common in certain models. In some cases, plastic parts may be more susceptible to failure due to under-dimensioning or the effects of compression and stretching cycles. It is important to select the appropriate plastic material to minimise noise, damping issues, friction, and wear.
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They are quieter than metal tensioners
While it may not be entirely accurate to refer to some timing chain guides as plastic, manufacturers do use highly engineered resins and structural fibres in their construction. These materials are designed to withstand high temperatures, engine oil, and harmful vapours within the combustion chamber. They are also designed to endure thousands of heat cycles.
The use of plastic in timing chain tensioners offers several advantages over metal alternatives. Firstly, they are much quieter than metal tensioners. If a guide were made of stamped or cast metal, there is a risk that sound would be transmitted from the engine to the vehicle. Even cast metal guides often feature plastic inserts that contact the chain.
The gliding of metal over plastic in a large, flat area, as seen in modern plastic arm-type tensioners, is another reason why plastic is preferred. Additionally, plastic guides require a shorter range of adjustment than a sprocket. When pushing at a single point, a sprocket would need a longer adjustment range as the chain stretches over time.
Plastic timing chain guides are designed to last the engine's life, but abnormal wear patterns can indicate a chain system problem. Premature wear can be caused by issues with the path of the chain, lubricants, or tensioners.
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They require less adjustment than sprockets
Plastic timing chain tensioners are made of highly engineered resins and structural fibres. They are designed to withstand high temperatures, engine oil, and harmful vapours in the combustion chamber. They also endure thousands of heat cycles.
Plastic timing chain tensioners are preferred over sprockets because they require less adjustment. Sprockets require the chain to wrap around them at a minimum angle, whereas a roller can contact as much or as little of the chain as needed. This means that when the chain stretches over time, a sprocket will need to be adjusted over a longer distance compared to a guide that deflects more of the chain.
Additionally, a sprocket would be noisier and wear out more quickly. It could also break teeth and damage the engine. Sprockets would also stretch the chain faster because they would have to apply more pressure.
The tensioner also damps chain harmonics when running and takes up any whiplash, especially during the most violent rotation action, such as shutdown. This helps to obtain the maximum life out of the chain and lowers harmonics and oscillations.
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Frequently asked questions
A timing chain tensioner is a component that works to keep the timing chain in tension, preventing it from fluttering or flopping when the engine speed changes.
Timing chain guides are components designed to keep the timing chain in place and prevent it from fluttering or slapping. They are typically made of highly engineered resins and structural fibres, sometimes referred to as plastic.
Metal timing chain guides can transmit sound from the engine to the vehicle, causing unwanted noise. Plastic guides and tensioners reduce noise and are designed to withstand high temperatures, forces inside the engine, engine oil, and harmful vapours.
Abnormal noises or correlation codes can indicate issues with the timing chain tensioner. Additionally, if the timing chain guide breaks or cracks prematurely, it may be due to a failed tensioner, lack of maintenance, or high mileage.
Failure to replace a worn timing chain tensioner can lead to a significant loss of engine power due to a lack of compression. The engine may also skip time or experience catastrophic failure if the tensioner is not replaced in time.
