Timing chain vs. timing belt

In my previous post I simply illustrate the importance of change the timing belt. It is such a pain in the neck that we need to pay over one grand to change timing belt because it is critical. It cost time and money. Certainly you can absolute do it yourself, however miss-timing will caused a catastrophically failure. Many of us would thing why we did not “invent” a non- maintenance timing belt or some equivalent thing so we can save some bucks. Actually before timing belt become popular in 70’s-80’s, most car manufacture use timing chain instead.

Timing chains have been widely used before timing belts popularity explosion in 70’s-80’s.Timing chains look just like the chain on a bicycle, but much greaser. The beauty of the timing chain is that they typically last a very long time. A few car manufacturers recommend replacing them at certain mileage or time intervals, while others claim that the chain is good for the life of the automobile. It really depends on the make and model of the car or truck. The downfall of timing chains is that they are heavier, generally known to be noisier, and if they do break, it is usually catastrophic to all of the surrounding engine parts.

Much like automotive timing belts, timing chains also have tensioners that keep the chain from flopping around. The difference is that timing chain tensioners are nearly always controlled with engine oil pressure. As you can imagine, if the engine oil pressure becomes low for whatever reason, the oil driven timing chain tensioners will lose pressure, and the mechanical engine timing becomes extremely erratic. This will cause poor engine performance and give the chain the opportunity to fail in grand fashion. The other benefit to timing chains is that they rarely have anything to do with the water pump. So replacing them at the same time isn’t nearly as necessary as it is with a timing belt.

Facts of timing belt and chain

– Timing chain requires a quieting shoe. In many cases one of them may serve both roles and two tensioner/quieter shoes could be used.

– Chain is usually heavier per inch length than belt and therefore require stronger infrastructure to hold it in place. In case chain get stretched over time and go above tensioner’s adjustment capability things could go hairy fast. Engine’s timing may become erratic.

– Timing chain in general is very reliable and requires only every so often check-ups.

– Timing chain usually enclosed within an engine case and constantly lubricated.

– Timing belt drive usually quieter than a chain drive. Since belt is lighter it requires lighter support structures and does not need a calming shoe.

– As a result SOHC/DOHC engines could have higher RPMs without worry of an added chain momentum.

– Timing belt must be changed every 50-75 thousand miles along with the tensioner and a water pump if one driven by the timing belt.

It is hard to say which one has the absolute advantage than the other. We know the in 2009 model year trend of car manufacturers moving back to timing chain engine design. Many of them rely on a service data and price/performance evaluation for the size of the vehicle. It is unlikely that general public will know exact figures on timing belt/chain price/performance comparison but we all have our own preferences and that may become a driving force for the future engine models.

Source:

http://www.crxsi.com/articles/read/what-s-best-timing-belt-or-timing-chain-february-2009.htm

http://mechanics.stackexchange.com/questions/2711/timing-chain-vs-timing-belt

http://www.1aauto.com/content/articles/timing-belts-chains

http://ezinearticles.com/?Timing-Belt-Vs-Timing-Chain&id=6463259

http://en.wikipedia.org/wiki/Timing_belt