Timing belt or chain?

[redpoint5]

The 1998 Camry I now drive has 240,000 miles on it, and my parents have had the timing belt break on it twice within the 120,000 miles or so they have owned it. Fortunately the engine is non-interference, and the car runs perfectly after replacing the belt.

Recently they purchased a 2002 Camry, and it has a timing chain.

Looking at this chart, it seems half of Toyota's cars use a belt, and half a chain. This got me to wondering why a manufacturer would choose one over another?

To my knowledge, a timing chain lasts much longer, requires no service, and is slightly more energy efficient at transferring power to the cams. What would be the reason for choosing a belt? Having to replace it every 90k miles makes any car with a belt less appealing.

[oldtamiyaphile]

Belts are quieter and cheaper to produce, lighter and more compact.

Chains can still break and camshafts can break from automatic tensioners over tensioning (eg Mercedes M111 engine).

At one point every car seemed to come with a belt, but now favour is swinging back to chains it would seem. Only my Skyline has a belt, and I just bought a VW with a gear driven cam.

Replacement intervals are normally ~60k for belts.

[cRiPpLe_rOoStEr]

Originally Posted by oldtamiyaphile

Only my Skyline has a belt, and I just bought a VW with a gear driven cam.

Gear-driven cams are good. Working on the tensioners is not so pleasant. We probably don't see newer engines featuring gear-driven cams since it doesn't seem to support VVT - at least I can't remember a single engine with both VVT and gear-driven cams...

[theicecreamman]

I'll take a chain over a belt anyday in a light duty engine, hate changing timing belts, but Gates has really stepped up their offerings with higher strength belts.

[niky]

You can implement VVT with gear-driven cams. The mechanism for variable timing is in the gear on the camshaft, anyway, and doesn't care whether it's belt, chain or gear driven.

But those systems are complex and noisy. Almost completely maintenance free, though.

Chains are lovely. Have hardly ever had one break or heard of one breaking, except as a freak accident. If I recall right, manufacturers started going back to belts for reasons of noise, as chains are a bit noisier than belts... but given direct injection is so clattery that they've resorted to using more insulation around the engine, I don't think the extra noise is much of a problem, anymore.

[redpoint5]

I don't recall ever hearing the distinct noise of a cam chain, and didn't even know that was a reason that belts were used instead.

I'm sure most people would prefer to have the most quiet ride they can get, but I'm among those that have removed the turbo silencer ring so that I can hear the music of the compressor spool. I guess that's a more satisfying sound than chain and gear noise.

[niky]

From owning years of Sentras with chain, I can tell you there's a distinct whine, but there should be no clatter, not unless the tensioners wear out (and they do).

But put beside the whine of the AC compressor, alternator, the accessory belts in general and the general underhood clatter, it's not really something that matters. At least, the only manufacturer I ever heard to claim a switch to belts was for noise was Nissan, with their Navara diesel (which ain't a quiet engine, anyway, not by far).

[some_other_dave]

Belts are quieter, and I think may actually take less power from the engine than a well-lubricated chain? They're also cheaper when manufacturing the engine, which I think is a pretty big concern for the car companies.

Chains, unless very short (e.g., old pushrod V8 timing chains) will need some sort of tensioning mechanism. These mechanisms can be finicky, and if and when they fail the chains can jam or break or simply jump time. In an interference engine, this tends to lead to very expensive damage, just like a broken timing belt would. Older Porsche 911s and 2007-2010 (or so) MINI Cooper S models seem to be relatively prone to such things. (Look up "death rattle" on a MINI board, or "chain tens" on a Porsche board to see what I mean.)

Both chains and belts have their upsides and downsides. I've been paranoid enough about the chain in my own MINI that I'm missing the belt in my old Honda. I replaced the belt every 60,000 miles--but some MINI owners are winding up replacing the chains short of that mark!

-soD

[Miller88]

I have posted this before (maybe not here) but I strongly dislike belts. They are a completely unacceptable cost cutting measure. The manufacturer saves $20 making the vehicle, only to cost the owners multiple thousands of dollars in maintenance over the course of the car's lifetime. If the maintenance is not performed, it's a few thousand for a replacement engine (assuming interference).

I will not own a car with a belt.

[cbaber]

My timing belt with only about 60k miles snapped on the freeway and left me stranded in 10 degree weather waiting on a tow truck for 45 mins. (I hate timing belts)

They aren't that bad, but when things go wrong, things go wrong. Luckily I didn't suffer engine damage, but most people need their heads rebuilt after something like that. I think Honda recommends timing belts every 90k? They aren't hard to change out yourself, but it's still a pain if you drive 30-40k miles a year and you have to worry about the belt. Actually for me the tensioner was the culprit that lead to the belt breaking, so that's a common problem between chains and belts.