Timing chains and timing belts (also known as a cambelt) serve the same function of synchronising the crankshaft and camshaft. Each has its own benefits and drawbacks, as explained in this article.
A timing belt or timing chain is an integral part of an internal combustion engine which synchronizes the crankshaft rotation and the camshaft to open and close the intake and exhaust valves at the correct time during each cylinder stroke.
What Do They Do?
The timing belt or chain's job is to keep the engine's timing accurate. Timing refers to the relationship between the camshaft, crankshaft, valves, and pistons.
The intervals between these crucial parts of an engine must always remain the same.
A belt or chain physically connects the crankshaft to the camshaft, and this connection drives pulleys or sprockets.
A chain drives sprockets, while a belt drives pulleys. Sprockets and pulleys work in tandem with a belt or chain to accomplish the same task.
The number of teeth on a camshaft pulley or sprocket will always be double that of a crankshaft pulley or sprocket.
The camshaft will turn once for every two crankshaft spins because to the varied number of teeth.
What's the Difference?
Timing chains and belts provide the same function. One is made of metal, while the other is a firm, rubber-like substance.
The architecture of the engine is affected by whether a timing belt or chain is used, aside from the fact that they are made of different materials.
It also has an impact on how often it needs maintenance and how long it lasts.
A metal timing chain is stronger and more resilient than a rubber timing belt because metal is more robust than rubber.
An engine will turn more than a million times in a normal day of operation, which translates to more than 30 million times in a month of operation.
Timing chains and timing belts resist wear and tear at different rates.
Metal resists wear and tear better than rubber. However, only when it is lubricated in oil does metal outlast rubber in terms of wear resistance.
This takes us to our first significant distinction between timing chains and belts; timing chains need oil lubrication to keep them from prematurely wearing out.
Oil leaks must be stopped by sealing a chain away from the environment.
You can quickly determine whether your engine has a timing chain or belt by looking in the engine compartment.
If the engine has plastic covers, it probably has a belt, but if the front of the engine has metal covers, it probably has a timing chain.
In comparison to an engine with a timing belt, an engine with a chain often needs a bit more space in the engine compartment and may be slightly heavier.
Timing chains have a substantially longer service life than belts because they are more robust.
Some timing chains are designed to endure the lifetime of the engine and don't require periodic maintenance.
There isn't a timing belt on the market that can endure the entire engine's lifetime.
Depending on the vehicle and engine, you must change your belt every 4 to 10 years, even if you don't run the engine.
Timing belts must be replaced because rubber naturally ages over time, even if it is not in motion.
Additionally, rubber belts perform poorly in hot environments and are also prone to damage from oil and coolant exposure.
As we all know, ambient temperatures may rise significantly in an engine compartment, which accelerates the wear of rubber.
The normal timing belt service period for a contemporary engine is between 60,000 and 80,000 miles.
However, the majority of vehicles produced in the mid to late 1990s used much improved timing belt materials.
Timing belts typically consist of rubber with fibre reinforcing materials such as kevlar or fibreglass fibres, which boost the belt's tensile strength.
The rubber itself is often made of neoprene, welded urethane, or moulded urethane.
However, rubber timing belts began utilising a substance known as HSN in the middle to late 1990s.
Highly saturated nitrile (HSN) is a substance that has increased tolerance for high temperatures.
Timing belt servicing intervals were greatly extended using HSN, whereas older engines generally have a service period of 15,000 to 35,000 miles.
While timing chains do have a service period of 80,000-120,000 miles, they are often noisier and generate more friction.
Because rubber is softer and lighter than metal, it operates more quietly and with less friction than chains.
Additionally, timing belts use less force to spin because they have less inertia, which lowers parasitic horsepower losses.
Rubber is also good at absorbing engine vibrations and harmonics, making an engine feel and sound smoother.
Types of Timing Belts & Chains
Timing belts usually have a very similar design and don't differ much from each other, there are two types of chains.
Silent type chains
Roller type chains
Silent Type Chain
As implied by its name, the silent chain is quiet. The chain and sprocket assembly's noise level is decreased by this type of chain.
Silent timing chains are rather common among manufacturers because they are easy and inexpensive to produce and more comfortable for the occupants of the vehicle.
A silent chain is made up of several links that are connected by pins.
The chain is turned by the sprockets, which have teeth shaped to match the profile of the links.
Roller Type Chain
The roller type chain employs rollers on these pins, and the rollers revolve on the sprocket's teeth as the chain turns the sprocket.
Less friction results in less parasitic horsepower losses, this kind of chain minimises friction, reducing power loss. It lessens the chain's localised wear as well.
Compared to quiet type chains, roller type chains are more costly and are also noisier.
There are two types:
Single roller chain
Dual roller chain
The dual roller type is more reliable, long-lasting, and difficult to break.
However it has a larger surface area and more friction, which results in increased parasitic horsepower losses.
Roller chains are more vulnerable to impurities in engine oil.
Timing chains are lubricated by oil but the lubrication is only as effective as the oil.
One of the following causes is nearly always to blame for premature chain stretch and failure.
The oil was not replaced promptly.
The oil had the incorrect viscosity.
The oil was of poor quality.
Any one of these three can considerably reduce the timing chain's lifespan and increase the likelihood of chain breakdown.
Oil that has been in the engine for too long is prone to harming roller chains. More pollutants will be present in engine oil that has been sitting for a long time without being changed.
These impurities may become lodged between the rollers and the chain's pins, speeding up its deterioration.
Timing chains are preferable as long as the correct oil is utilised and changed on schedule.
In contrast to a rubber belt, a metal chain is stronger and less prone to break.
All car engines were chain-driven in the 1950s and 1960s since belts weren't invented yet.
Chains then lasted as long as the vehicle, due to two factors.
Earlier cars did not go as far.
Engine power wasn't as high.
It was very rare to see a car with over 200,000 miles.
A unusual racing engine created by Bill Devin in the early 1950s was the first engine to ever employ a rubber tube belt.
It had horizontally opposed motorcycle cylinders and an overhead cam design.
With the technology at the time, utilising a chain was not practical because of the engine design.
As a result a rubber toothed belt was used instead, and the 1956 Sports Car Club of America championship was won by this car and engine.
The 1962 release of the West German Glas 1004 marked the introduction of the rubber timing belt powered engine in a mass-produced vehicle.
Its engine produced 42 horsepower at 5000 rpm.
It's interesting to note that BMW acquired Glas in 1966 for access to the timing belt patents rather than for the vehicles or the brand.
Timing belts saw significant growth of usage in 1966. The first rubber timing belt-driven twin-cam engine was unveiled by Fiat in 1966.
The Pontiac overhead-cam inline-six engine was the country's first belt-driven engine that same year.