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Old 28th February 2007, 17:47   #1
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Exclamation Timing (cam) belt vs chain

What is the advantage of belt over chain (or vice versa)?

I heard that if a timing belt snaps, the piston can just knock the valves causing severe (and expensive) engine damage. While faulty timing chain won't allow the engine to run.

I wonder why more cars are using belt instead of chains? Is it just to save money? In most cars belts need to be changed at 60,000 km where as chains usually last over 150,000 km (often the lifetime of the engine).

Any thought?

PS: if you wonder, cam belt/chain controls the precise opening timings of valves in the cylinders.
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Old 28th February 2007, 17:57   #2
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Belt has very less noise compared to chains. But snapped belt can lead to catastrophic damage in the engine. Most modern cars have belts.
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Old 28th February 2007, 18:41   #3
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Chain has longer life, but replacement is expensive. Many modern engines have timing chains now instead of belts
Timing belt - Wikipedia, the free encyclopedia
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Old 28th February 2007, 18:51   #4
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This link has a good explanation of timing belt
Timing Chains, Gears & Belts

but it described two different types of engines, in one (free wheel) no damage is caused if timing belt snaps and in other, pistons may smash valves...

I don't think owner's manual provide enough info to know what type of engine you got :(
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Old 28th February 2007, 19:00   #5
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Nice links.

At the rate they work and pressure they have to sustain, chains will loosen or stretch at least after a period of time. That can change the timing altogether and slowly cause damage to the engine. In that case, your mileage will suffer too.

Belts are a better option. But someone who doesn't know head or tail about Timing Belts has to suffer, right?! Since it may eventually snap, and cause damage.

Last edited by Gordon : 28th February 2007 at 19:07.
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Old 28th February 2007, 19:12   #6
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I recently heard about the catastrophe when a Sumo engine's timing belt snapped.
The valves broke,piston chipped ,Disconnected Conrod moved horizontally instead of moving vertically and broke the engine block into two.
And so,they picked up a used engine for 8000 bucks at Pudupet(Gujri).
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Old 28th February 2007, 19:50   #7
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Most petrol engines run chains, whereas diesels run belts.

Although I believe belts are taking over chains as the preferred drive, since belts are lighter, do not require lubrication, and provide lesser load on the cam gears to run efficiently. On the flipside, belts have a shorter service life. Nevertheless, you can extract more performance from an engine if the cams are belt driven- theoretically.

Just an indication as to what happens if you don't pay attention to manufacturer's recommendations regarding service intervals. I witnessed this particular incident personally...



Any guesses as to which engine this is?
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Old 28th February 2007, 21:55   #8
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Main differences in their failure:

Timing chain: Engine power loss, valve clatter, rough running

Timing belt: Engine might stop running or valves might crash into pistons.


Adv/Disadv:

Timing chain's + point: Typically lasts an engine lifetime

Timing chain's -ves : Less efficient, noisier, more expensive than a timing belt.

Advatnages of timing belt: Less flexing resulting in better camshaft timing/efficiency.

Timing belt's disadvantages: Needs to be replaced at specified intervals.

Last edited by theMAG : 28th February 2007 at 22:01.
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Old 28th February 2007, 22:29   #9
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Quote:
Originally Posted by Gordon View Post
Nice links.

At the rate they work and pressure they have to sustain, chains will loosen or stretch at least after a period of time. That can change the timing altogether and slowly cause damage to the engine. In that case, your mileage will suffer too.
Both belts and chains will stretch over time. Both need a tensioner to maintain the tension.

Chains are also narrower than belts and in todays tight engine compartments, it can help a lot.

If its an interference engine, chains are the way to go, but I dont think they are lubricated with oil.
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Old 1st March 2007, 01:43   #10
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i also remember seeing somewhere that belt/chain needs to be advanced at high RPM, to keep the burnt fuel (wavefront) in sync with the piston.

I am guessing belt will cooperate well in such scenario, rather than chain which has fixed length links.
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Old 1st March 2007, 02:21   #11
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Quote:
Originally Posted by veyron1 View Post
Any guesses as to which engine this is?
Looks like TATA Indica or sumo
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Old 1st March 2007, 03:38   #12
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Or you could just run gear-driven cams.
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Old 1st March 2007, 04:02   #13
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Like the Enfield Bullet. The noise will drive you nuts.
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Old 1st March 2007, 10:15   #14
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There's another type of gear driven cams present on the Ducati's, they're called bevel heads. The cams are run by a bevel gear shaft which travels up to the cylinder case through a tube which looks like a pushrod tube.

Gear driven cams suffer the same drawbacks as a chain and shares the same pros plus another it never stretches and timing never changes under any engine condition. Lubrication is very important in gear driven types, moreso than the chain drive types.
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Old 1st March 2007, 14:49   #15
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Quote:
Originally Posted by Mpower View Post
Like the Enfield Bullet. The noise will drive you nuts.
Or the RC45. That'll drive your nuts.

Quote:
Originally Posted by veyron1 View Post
Most petrol engines run chains, whereas diesels run belts.
Eh? Are you sure?
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