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Car Care: Chains cranking up in popularity
AA Motoring discusses the engine cambelt v chain debate
Basic principles of the internal combustion engine haven’t changed over the years — it’s still the typical suck, squeeze, bang and blow.
We’ve seen advancements in technology to improve the efficiency of engines, such as the increased accuracy of fuel injection systems and the common rail diesel injection, but underlying principles have always been the same. The crankshaft still drives the camshaft through a chain or cambelt to keep the engine components in time while running.
Until the 1970s, it was common for cars to have a chain-driven camshaft, but in the 90s the cambelt was adopted to help reduce the noise of engines. Since around 2005, most manufacturers have chosen to revert back to the chain system as consumers wanted lower maintenance costs, but they’ve spent a considerable amount of time and effort introducing improvements that eliminate many of the drawbacks of the older systems.
Cambelts, or timing belts, are made of rubber and high-tensile fibre, so they’re usually quieter than chain-driven vehicles.
Typically, they’ll need to be replaced between 60,000 and 100,000km, but it can also depend on the age of the cambelt — and the manufacturer’s specifications should be taken into consideration as well. Most systems will also include other components that may need to be periodically replaced, such as the idler, tensioner and water pump.
Cambelt replacement is one of the most common and costly maintenance jobs for a vehicle, so it’s important to budget for it. The most thorough way to replace a cambelt is to replace all the components at the same time and since the engine needs to be stripped during replacement, there is the perfect opportunity to easily access other components.
If you don’t replace components and they later fail, it can result in catastrophic engine failures.
Chains, or timing chains, are back in fashion, and cambelts are becoming few and far between. Even though chains lasted longer and were stronger, the older systems used to rattle and tended to generally emit more noise, particularly as the engine became more worn down.
Chain systems have improved dramatically though, with manufacturers introducing innovative ways to reduce noise.
As well as changing the material used, they have improved the tensioning system through the introduction of oil pressure and spring-loaded tensioners, which helps to keep the chain taut and quiet. Modern engines also employ large chain guides to silence the chain and minimise vibrations. Although chains don’t tend to break, they can stretch over time due to wear and tear. Look out for signals of a stretched chain such as rattling noises from the chain cover, and engines that are slow or hard to start.
Some vehicles even have an engine management sensor which alerts you with a warning sign on the dashboard if the camshaft and crank shaft are not synchronised.
Chains are designed to require less maintenance, which means that servicing costs will be less — but if a chain does become worn, the cost of replacement can be significantly higher than that of a regular cambelt replacement.
It’s important to note though that this is a rare occurrence, and so the general maintenance of a chain-driven vehicle is likely to be less than that of a car with a cambelt.
Developments for alternative valve train systems have been tested by a Swedish company called FreeValve.
Since the early 2000s, they have been developing and testing systems with no camshafts.
Although there may be many advantages of these engines, there are clearly still hurdles that need to be overcome because we haven’t seen many vehicles produced that are using this type of technology.
Both chain and cambelts do the same thing, but consumer desire for low maintenance costs has seen the increased popularity of chain systems in cars.