why a timing belt over a chain?

[mjhandy]

I've always wondered why not a chain driven system rather than a belt? Wouldn't a chain last longer?

 

[tditom]

the chain would last longer than a belt, but both wear and stretch. the belt tension is easily adjusted as the belt stretches. Chain (and other components) would still need to be changed eventually (maybe by 500K km?). the chain would need to be lubed. chain is noisier.

look at it this way: the complete path of wear parts is being renewed every 160K km using a belt for a cost of approx 265 km/$.

 

[HopefulFred]

Many chains last longer, but don't (as I understand it) perform to the same standards or, generally, deal with as high loads as vw requires.

The question is, why not a serviceble system which maintains very precise control of timing? The answer is the timing belt.

Consider the BMW is saw in the shop this week - less than 200K and a broken timing chain tensioner - 32 hours labor to remove the engine and replace the chain and tensioner. Or the Ford I saw two weeks ago - over-revved and broken - no start.

The belts, on the other hand, don't stretch, don't rattle (like old Altimas and plenty of other old engines), and require regular service.

I'm happy with this compromise.

 

[grizzlydiesel]

also might have something to do with diesel operation, diesels have much higher... not sure of the right term here, "shock loading" perhaps? than a gasoline engine. The resulting noise and vibrations from a chain driven system are fine for a semi truck with a detroit diesel, but in a passenger car, comfort and such things are priority. Im sure the belt was a better choice based on those standards.

keep in mind, that for 2009, all gasoline engines from VW are timing chains, but the 2.0L TDI is still a timing belt. im sure there is a reason.

 

[i_dont_golf]

what about the indestructible old mercedes diesels? they all have timing chains. and just noise is no excuse.... you drive a diesel car. would you really hear the timing chain much?

 

[TDICADDGUY]

Ahh crap not this again.

This has been discussed before, many times. Do you know very much about timing chains and their issues on OHC engines? I see that the low-revving and overbuilt MB diesel has already been brought up. You can't compare it to a small high-revving Volkswagen diesel....apples and oranges.

Chains do wear out and it is much harder to make a chain perform reliably in an OHC application. Look at the difference in length between an OHC and an OHV engine. Chains and all the tensioner getup would be much more expensive to replace as well.

The VW belt system (with 100k components) gives reliable, noise-free and maintenance-free service for 100,000 miles. $300 in parts if you replace it yourself. ~$800 to have a TDI guru do it. That is pretty cheap for a 100k mile interval.

 

[Lug_Nut]

Chains last 2 to 3 times longer and then cost 4 times as much to replace.

 

[mjhandy]

thanks guys. didn't mean to rehash something, but it was something i'd always wondered about.

Cheers

 

[Matthew_S]

In most cases a chain wil last the life of the car. In many cases the chain will be the thing that ends the life of the car.

 

[Velocity1896]

I wouldn't take either, I prefer gear drive. Even though its would never happen in TDIs. I have done tons of work on Detroit Diesel Series 60 engines and the old 6V92s. They both use a "Bull Gear" in place of a timing belt or chain. Granted this is a whole realm, but I have seen gear drive on some older muscle cars, it is a bit noisy but you never have to replace it. Granted you will get some metal in the oil due to gear backlash, but it has never been an issue. As long as it doesn't get too much play its good to go. OK i'll shut up now

 

[Lug_Nut]

Gears are heavy and their rotational inertia adds to the same apparent power loss as a heavy flywheel or larger brakes or larger tire and wheel sets.
Yeah, I have a geared cam drive on my 1.5 liter V4 Saab. A big slow revving class 8 OTR truck won't mind the extra spinning mass, but a 2 liter definitely does.

 

[oldiesel]

Actually the chain in my 300d 2.5 Mercedes was much easier to replace and also less expensive than the belt and related hardware on my Jetta and the Jetta is the easiest of the TDIs as it is an AHU.The Mercedes had over 240,000 miles when i did it just as a precaution as it was showing more than 5deg of wear.Sort of comparing apples and watermelon as there is such a great difference in the price these cars were built to, i guess MB could afford to build a longer lasting system. Don

 

[weedeater]

I always ask myself this question whenever I see a Harley go by with a belt rather than a chain.

 

[mrGutWrench]

Actually the chain in my 300d 2.5 Mercedes was much easier to replace and also less expensive than the belt and related hardware on my Jetta and the Jetta is the easiest of the TDIs as it is an AHU.The Mercedes had over 240,000 miles when i did it just as a precaution as it was showing more than 5deg of wear.Sort of comparing apples and watermelon as there is such a great difference in the price these cars were built to, i guess MB could afford to build a longer lasting system. Don

__. Talk about comparing apples to oranges! The old MB's are big, slow-turning engines with compact timng system layouts. Chains are imprecise and don't like revs. A chain on a TDI would be whipped to a frazzle. A chain would be a bad choice for a TDI, as much as for the imprecision of the timing as anything else. A few degrees on a TDI and valves are intimately associated with pistons and that means a head rebuild 99% of the time. Chains "stretch" and have imprecise tensioning systems. Chains would not be good on a TDI. The belt is about as good a system as you'll get.

 

[mrGutWrench]

Ahh crap not this again.

This has been discussed before, many times. (snip)

__. But don't you unnerstann? Mah gran-daddy had a flathead Ford peekup truck - changed the awl ever 1000 mahls with 99 cent a quart awl fum the Wawmott and thet truck ran over 200,000 mahls. An it hed a tahmin chain. Whutt's gudd enuff fer that truck oughtta be gudd enuff fer them flimsy little furrin thangs!

 

[Nico3d3]

I had a Nissan Sentra before my Golf and I never had any troubles with the timing chain. It was a recent car though (90 000km). By the way, I fail to see why we can't get timing chain in our small TDI engine like the 2.0 CR-TDI while VW is already using it on the V12 TDI?

See image (image was too big to include here and I'm too lazy to reduce its size and reupload)

 

[tditom]

I wouldn't take either, I prefer gear drive. Even though its would never happen in TDIs. ...

really? ever hear of the v10tdi?

 

[roadhard1960]

My Toyota 22REC has an overhead cam, a timing chain and interference valves. I think the first chain lasted over 250,000 plus miles. Chain was ok but tensioner goofed up. I can assure you it was no $300 in parts to RR the chain. Gas engine does not have the violent explosions the TDI has.

 

[TDIJetta99]

I always ask myself this question whenever I see a Harley go by with a belt rather than a chain.

You talking about the primary drive or the drive to the back wheel?

Open belt primary is ALL flash. It's the "cool" thing to have. Damn expensive too..

Rear wheel belt drives are nice.. less maintenance, last longer (usually), less noise, smoother..

My road bike has a gear driven primary setup, belt drive to the wheel..

 

[need4speed]

belt, chain, I don't care. Just engineer the damn thing so it doesn't take all day, special tools, and a computer timing job to replace it. Pain in the keister.

 

[TDIJetta99]

belt, chain, I don't care. Just engineer the damn thing so it doesn't take all day, special tools, and a computer timing job to replace it. Pain in the keister.

You must not work on cars for a living.... TDI timing belts are EASY compared to a number of cars out there... Ever mess with the chains on a ford OHC explorer? THAT takes all day.. How about a "simple" valve cover gasket on a 4.2 trailblazer? hehe.. give me the TDI's.. they are simple and easy..

 

[tditom]

belt, chain, I don't care. Just engineer the damn thing so it doesn't take all day, special tools, and a computer timing job to replace it. Pain in the keister.

what is your point of reference for simplicity? i guess it is complex next to a carburated push-rod engine.

 

[Keith_J]

Chains require lubrication. Which would make the front covers much more complex as well as have a drain back to the crankcase. Another point for oil leaks? And that would be a difficult job to fit it all in. And then the water pump? That weep hole would now communicate with the crankcase so instead of a coolant leak, you would have to flush the oil system. If caught early enough.

 

[Keith_J]

belt, chain, I don't care. Just engineer the damn thing so it doesn't take all day, special tools, and a computer timing job to replace it. Pain in the keister.

All day? It can be done in 3 hours if you have the proper tools. And if you are good, no need to mess with the fine tune on the IP.

 

[ahardy4]

Haven't done a TB on my Jetta yet, but after reading some threads it does sound a bit more complicated than the gasser TB's I've done (88 Prelude, 98 Volvo S70) which were both OHC engines. For the gassers no special lock down tools were required (well actually the prelude required two drill bits to hold the cams in place...), and there certainly wasn't any need for a computer to set timing. So from my perspective it does seem a bit more complicated, but so far I've found the Jetta easier to work on than some cars of wrenched on.

 

[ahardy4]

Chains require lubrication. Which would make the front covers much more complex as well as have a drain back to the crankcase. Another point for oil leaks? And that would be a difficult job to fit it all in. And then the water pump? That weep hole would now communicate with the crankcase so instead of a coolant leak, you would have to flush the oil system. If caught early enough.

I agree. I had a 93 MB 300E and that cover was a pain to keep leak free. The timing belt system is much easier to deal with IMO.

 

[DPM]

It's worth noting that some very modern diesels have reverted to chains. My father's Yaris and my Subaru are both chain driven.

 

[nortones2]

Indeed. Honda use a chain on their diesels, as well as their car engines that reach 8000 rpm. The timing precision does not seem to be affected by choosing a chain drive.

 

[TurbinePower]

Gears are heavy and their rotational inertia adds to the same apparent power loss as a heavy flywheel or larger brakes or larger tire and wheel sets.
Yeah, I have a geared cam drive on my 1.5 liter V4 Saab. A big slow revving class 8 OTR truck won't mind the extra spinning mass, but a 2 liter definitely does.

Sorry, I have to jump in... V4 Saab engine? What year? Model? Availability of parts?

I lust after a V4, even if it's just as a conversation piece... a sub-two-liter V4 is even better...

 

[GoFaster]

Saabs at the very beginning used two-stroke engines. When it became necessary to go to 4-strokes in the early 1970's, they bought a V4 engine from Ford of Europe at the time. I don't know what Fords it was originally used in.