When experts start considering the tradeoffs in the construction of a car's engine, one As we will discover in this article, there are pros and cons to both.
To begin, we'll look at what these two automotive parts do, how they're different and how they are the same.
What Are Timing Belts and Timing Chains?
What does a timing belt vs timing chain do? Both parts perform the same function: they synchronize the rotation of your engine's camshaft with the rotation of your engine's crankshaft.
Not a Serpentine Belt
The timing chain or timing belt should not be confused with the serpentine belt. Earlier automobile engines used several belts connected to crankshaft pulleys to power various automobile accessories, such as the cooling fan, alternator and air conditioning compressor.
In later model automobiles, the manufacturers replaced this multiple-belt configuration with a single belt that powers all these accessories.
That belt is called the serpentine belt. If the serpentine belt breaks, the engine still runs but the accessories stop working. If the timing belt or chain breaks, the engine stops.
Timing Belt vs Timing Chain's Operation
In your car's engine, the camshaft is precision engineered to maximize your engine's power, reduce its emissions and provide excellent fuel efficiency.
To ensure you get the maximum benefit of the camshaft's engineering, your timing belt or timing chain needs to be precisely timed with the movement of your pistons through the four strokes of your engine: intake, compression, power and exhaust.
Each valve must open and close exactly in synch with the intake and exhaust strokes for proper engine operation.
What Drives What?
The crankshaft receives the power from the power strokes of the pistons. This rotates the crankshaft and, through the timing belt or chain, rotates the camshaft.
What Is the Difference Between the Timing Belt vs Timing Chain?
Until the 1960s, almost all automobile engines had timing chains to synchronize crankshaft motion with the camshaft rotation.
When rubber composites reached the point where belts made of these composites could stand up to the heavy-duty heat and power requirements of a car's engine, auto manufacturers began the transition away from timing chains to timing belts.
However, some manufacturers are returning to timing chains, with mixed results as we'll discuss further on in this article discussing timing belt vs timing chain.
Cons of Timing Chains
Why did car manufacturers switch from timing chains to timing belts? There are a few drawbacks to the timing chain, which we'll discuss here.
Timing chains cost more to manufacture than do timing belts. This cost of manufacture reduction makes automobile manufacturers able to produce engines at a lower cost, which results in a lower cost car for the consumer.
This reduction in initial cost to the consumer gets pushed out in time, as we'll discuss later on.
Oil Pressure and Lubrication
For a timing chain to operate properly, the chain has to be kept at a certain tension. Too loose and the chain can slip.
Too tight and the chain can break. As with any moving part, a timing chain needs lubrication.
Timing chains are held at the proper tension by oil pressure pressing on the tensioners. If the oil pressure drops significantly, the tensioners can loosen, resulting in possible chain slippage.
Timing chains are metal, as are the gears they drive. They make a clattering noise when in operation, which increases overall engine noise.
Reduced EFI Power
Engines that use electronic fuel injection (EFI) have computers that listen for the sound of engine knocking. Engine knocking occurs when the air-gas mixture prematurely ignites because of hot spots in the cylinder or cylinder head.
When the computer hears knocking, it backs off the engine timing to fire the spark plug earlier. This reduces the power the engine produces.
Timing chain noise can mimic the sound of engine knocking, resulting in an unnecessary reduction in engine power and fuel efficiency.
Weight and Complexity
Timing chains are heavier than timing belts, and their tensioning and lubrication needs increase the complexity of timing chain driven engines.
Manufacturers saw the advantages of the timing belt vs timing chain in their manufacturing cost and reduced complexity. There are some drawbacks to a timing belt, as we'll discuss here.
Pros of Timing Belts
As we discussed with timing chains, timing belts have some significant advantages. Two come immediately to mind: reduced noise and complexity.
Timing belts are much quieter than timing chains. This reduces engine noise and lowers the sound level inside the passenger compartment.
Timing belts are simpler in function than timing chains. They don't require any lubrication and have manual tensioners rather than oil-pressure driven ones.
Timing belts are better at absorbing shocks. In certain high-revving engines, such as those found in NASCAR, that shock-absorbing quality can help with engine life.
Cons of Timing Belts
The biggest con of timing belts is their longevity, or lack thereof. Manufacturers recommend replacing your timing belt every 60,000 to 100,000 miles, or every five to seven years, whichever comes first.
A timing belt replacement can run $1,000 or more. What the consumer saved on the front end by buying a less expensive automobile comes due on the back end when it's time to replace the timing belt.
Most car manufacturers recommend changing your water pump at the same time you change your timing belt.
The timing belt powers the water pump, and the water pump's useable life is about the same as the timing belt.
Symptoms of a Bad Timing Belt or Chain
How do you know if your timing chain or timing belt needs replacement ahead of the manufacturer's recommended mileage or time? We'll discuss that, but first, we should talk about the differences between types of engines.
Interference vs Non-Interference Engines
So, you're tempted to push your manufacturer's recommended timing belt replacement limit. What's the worst that could happen, you think?
The engine stops, you coast to the side of the road, and you call roadside assistance to give you a tow to your mechanic's shop. Not that big a deal if it allows you to push out a $1,000-plus repair bill.
Not necessarily. Before taking that step, you'd better find out if you have an interference or non-interference engine.
Picture your car's engine running along happily. The camshaft is timing the valves' opening and closing like, well, clockwork. But now the timing chain or belt breaks, and the camshaft stops rotating. Chances are good that some valves will be open when this happens.
Interference engines are so-called because the valves, when fully open, occupy the same space as the piston does when it reaches the top, or near the top, of its stroke.
If you have an interference engine, then your timing belt or chain breaking may very well result in your piston slamming into one of your open valves.
In that case, it's not just a timing belt replacement, it's an engine rebuild.
How do you know if you have an interference engine? Contact your automobile dealer or mechanic and ask them.
If they tell you you have a non-interference engine, you should be all right. If they say you have an interference engine, it's not a bad idea to check with another source.
How Do You Know It's Going Bad?
Your timing belt can stretch, and ultimately may slip a little. How do you know? Here are a few warning signs that can help you self-diagnose a timing belt problem:
If you notice an increase in engine noise, it could be a symptom that your timing belt is stretching.
Check Engine Light
Your automobile engine has a sophisticated computer system that is monitoring hundreds of functions during your engine's operation. If the computer senses that something is amiss, it will turn on the check engine light.
The check engine light may come on for something as innocuous as a gasoline filler cap that is too loose, or something as potentially damaging as a slipping timing belt.
Because it's monitoring so many things, it's impractical to have a panel light for each of them. Instead, your car's engine monitoring system stores a code that your auto mechanic or dealer can read using a special device.
If the monitoring system senses a problem with a slipping timing belt, it will turn on the check engine light and store the appropriate code.
Misfiring or Backfiring
Today's computerized ignition and fuel systems make a properly running engine almost impervious to backfiring.
If you hear a backfire, particularly if it is coupled with a check engine light, get to your dealer or mechanic as soon as you can, particularly if you have an interference engine.
Back to the Future
We mentioned earlier that manufacturers are slowly moving back to timing chains. Why is that?
When we purchased our shiny new automobile, one thing the salesperson didn't bring up was the cost of long-term maintenance.
We all know that, during our car's first 100,000 miles, something out of warranty may occur. But we also think of scheduled maintenance as a $50 oil change, or $300 major service.
What consumers didn't expect was that a single scheduled maintenance procedure will cost well north of $1,000. Gosh, our salesperson never mentioned that!
He or she also never told you that avoiding that expensive procedure could end up in you having to pay for a new engine.
Consumer dissatisfaction with this very expensive scheduled maintenance procedure is forcing manufacturers back to the long-lasting timing chain, particularly in higher-performance engines.
Problems With Timing Chains
Some auto manufacturers report that, with today's higher-powered engines operating at hotter temperatures, some timing chains are becoming prone to failure.
Make sure to review articles in auto magazines about this issue if you're looking to buy one of these cars.
So now you know the differences between timing belt vs timing chain. Armed with this knowledge you'll be able to make a better, more informed decision the next time you are in the market for an automobile.