Why timing belts?

MrMetal

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I'm trying to figure out why our TDIs have timing belts and not timing chains. What are the pros/cons of each?

Just eager to learn
 

BawlsyTDI

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Mar 21, 2001
TDI
jetta, someday a getta, 2001, baltic green
chain's tend to be noisy. Though with diesel clatter, who know's why the TDi doesn't have a chain. It sure would make life easier...
 

RiceEater

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gray 2k2 Jetta GLS
Thousands and thousands of years ago Jaguar (I think ~1950?)was among the first overhead camshaft pioneers. This got rid of the pushrods, rocker arms, quadruple valve springs, etc. Unfortunately this ran on something a little smaller, maybe larger, but I forget>>I remember, than a bicycle chain. If the chain held together it was sweet and smooth. If it didn't, it was kinda like me and my severe Alzheimer's. Anyway, ChemE's got better and better and so did the belts. This offered cheap dependable belts that were quiet versus more expensive noisy chains. Gear drive would mean huge expense. There are other options available to engineers but I forget.
The vast majority out there at the time was pushrod V-8s with valve trains running on nylon gear teeth and short multilink chains. To offer a OHC like the Jag or better would mean more noise or more valve train friction. During the 70's Bear you could only get 5 gallons and only if your license plate ended in an odd number. This environment established the reinforced rubber belt as the small OHC tradition.
 

MOGolf

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Chains require constant lubrication. This makes the engine more expensive to manufacture. That would push the price of the car above what the targeted market is willing to pay.
 

tdibugman

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Forked River, NJ
Chains require constant lubrication. This makes the engine more expensive to manufacture. That would push the price of the car above what the targeted market is willing to pay.
While I understand the thinking, it makes no sense.
We all paid MORE money for a TDI to begin with; if it costs them 100 bucks more for a chain, charge me 300 more: if it means I don't have to change a belt, the better off I am.

OTOH, I still have the Bug, but have bought 2 new Saabs: a 9-5 and
9-3SS. Both have, to my delight, surprise and joy, proper timing chains, to never be replaced or messed with.
 

Frank M

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Chains rob horse power
Belts don't (not as much)

As far as costs go, a Ferrari Testarossa $200,000 has a timing belt that has to be replaced every 15,000 miles or 3 years.
Engine has to be removed and the average cost for the job is $5-6000

You would think if money were no object as in the above example they would put a chain in. However power is the more important. All 475 HP
 

tdibugman

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Forked River, NJ
I still don't buy that reasoning.

A family friend happens to be an F355 F1 driver. His t-belt gets changed every 30K miles - almost the 40K my New Beetle requires (he has 135K on it now). Its a 3500 dollar operation. But, I would also suggest that to this guy, 3500 bucks is probably what he lost in AC last weekend. So, form an economic standpoint, if you can swing the payment, you can swing the maintenance. BTW - for 3500, they do A LOT of other service while its in. (12 qts Mobil 1, pads/rotors, etc)

What TDI owners are forced to spend (most of them anyway) is downright ridiculous based on the cost of the car. My dealer quotes about 700 dollars for a change. The last time I checked, VW is still a peoples car, and is driven by folks who work hard for their money and to pay off their car. the least VW could do is put in a damn chain!!!
 

banzai

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My mother now drives a 1994 Nissan Sentra- the little one.

It has a twin-cam chain driven valvetrain. Not a big deal or a selling point to them but something I noticed.

My 1970 Toyota truck had a nice OHC (18R-U) driven by chain, as does my brother's 1972 MBz 220
 

nortones2

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Formerly Passat 1.9 110hp
Toyota Yaris (Echo in some markets?) diesel 1.4, petrol Yaris's, Honda 2.0, Ford (some) all have chain cam drives. Can't cost too much! We on the other hand have (but not for much longer) a VW 1.6 gas engine Vento (Jetta) which mangled its valves when the belt broke at 72k. A chain cam car will soon arrive:)
 

RiceEater

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There are a huge number of incompetent mechanics out there breaking timing chains. Timing chains do need to be replaced, albeit at a lesser frequency than belts. A lot of mechanics would check ignition timing but failed to check the spark advance mechanism throughout its rpm range. A characteristic of a timing chain well beyond its time is timing fluctuations as rpms decrease. There is an established history of pushrod engines mysteriously failing shortly after being tuned by a "good mechanic." Anyway, just wanted to remind everyone that the timing chain does not eliminate but only extends the change interval.
 

GoFaster

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2006 Jetta TDI
Timing chains usually (note: USUALLY!!!) don't fail catastrophically, at least not on OHC engines that have long timing chains with plastic guides and spring-loaded tensioners (this is the way practically every motorcycle engine is, and it's the way a Toyota 22R or 2TZ is, and it's the way most other OHC auto engines that have timing chains are). Usually if something goes wrong, they start making a helluva racket which prompts the owner to investigate. Timing belts just go bang, bye-bye engine ...

I had the timing chain done on my '94 Kawasaki at 88,000 km because it was making a racket. I never touched the timing chain in either my Toyota 22R or the 2TZ.

None of these chains have any lubrication specifically for them. They run in the lubricated portion of the engine and get splash lubrication from everything else - there's no oil feed explicitly for the timing chain - lubrication is not a big deal, it just has to be on the oily side of the engine covers instead of the dry side.

I don't buy the power-loss thing. Motorcycle engine manufacturers work very hard to get maximum power output and everyone except Ducati uses chains!

I'd rather have a chain in there ... in fact, with the TDI's lack of need for high revs, I'd be fine with pushrods and a gear driven cam low on the side of the block ... a Cummins is like this ...
 

RiceEater

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GoFaster,
All good points. I just want to say that in this environment you would be asked about the noise coming from your OHC chain. I contend that most of your workarounds would involve more friction which leads to some power loss. But of course this is not an engineering forum though a few members are so open minded and eager to learn.
 

nortones2

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High Peak, UK
TDI
Formerly Passat 1.9 110hp
The missing word is "greatly"
Belt drives have no lube, and maybe they don't need it- but they do fail early, and require changing at say 40k to 60 k. What is the life of a single chain drive - 150,000 at a guess? Guess which method cuts out the incompetent meddler until the second or third owner? BTW Jags used to use a duplex drive for their old inline 6. I suspect that lasted until the tin-worm had done their worst.
 

POWERSTROKE

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2002 Golf
Timing chains usually (note: USUALLY!!!) don't fail catastrophically, at least not on OHC engines that have long timing chains with plastic guides and spring-loaded tensioners (
I had a 70 Nova with a 400 Big Block. The chain doesn't break. It can loosen and stretch, you may not notice either. One day I had trouble starting it. It finally started, ran a little crappy. Drove around the block, came to the stop sign and smoke was billowing from under the hood after it stalled. Chain skipped teeth and engine went out of time. Blew large amounts of gas through the carburetor and went on fire. Done. Car sole, motor junk. No difference. 110k on the car. Ran like a top right before then.
 

BawlsyTDI

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TDI
jetta, someday a getta, 2001, baltic green
Some models of Harley's use belts for the final drive, no?
yes, quieter, cleaner, longer lasting, lighter
Too bad the rest of the bike isn't quieter, cleaner, longer lasting, lighter, etc, etc, etc...
 

POWERSTROKE

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HAHA...Harleys are just like VW's. They require an owner that needs to pay extra special care to them. If not, the bike is not for you. They last a long time and hold their value. They are not as reliable as a Honda or say Kawasaki, but are much cooler. They are supposed to be loud. I think the V-rod may be the answer to Harleys problems. Designed by Porsche.
 

Frank M

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yes, quieter, cleaner, longer lasting, lighter
Too bad the rest of the bike isn't quieter, cleaner, longer lasting, lighter, etc, etc, etc...
I bought a new evolution Harley in '87. I put 72,000 miles on it in 5 years. Original everything except a few minor to be expected items. Burned no oil. And leaked no oil.

When I was a kid I had a '47 and it was a real undependable bike. I went English and they were no better. I was one of the first in my crowd to go Japanese in '64. When Harley got their act together in '80s, they started building a good bike.
 

Jetter_Sprinta

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I don't buy for a second the "noise" argument. It's got to be the money. The savings go in the auto makers pocket for sure. Lets not forget "job security" for dealerships with their "service specials".
Belt or chain I thought the only reason you would lunch a motor due to belt failure was because of valve clearance. That whole piston banging into the valve thing. Some motors do it, some don't. I jumped time on a Dodge 318 once. No big deal. Car ran fine after replacement.

Sprinter Van: 2.7 CDI chain driven cams.
 

Drivbiwire

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2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
Work with me here and think long term ownership and maintenance costs:

How many wearable parts are in a timing belt set up?
-Belt
-Tensioner

How many wear able parts in a timing chain set up?
-Chain
-Crank gear
-Cam gear
-Injection pump gear
-Nylon Guides
-Tensioner

I see the arguement already...I never replaced the sprockets on any of my other vehicles...CORRECT! Try running a TDI with 1 tooth of slop on the cam because you did not replace all the chain sprockets and guides...BOOOM you just bought a head.

A timing chain is simply not viable in a TDI application. My father just had to buy a new Mercedes diesel engine because his timing chain ate itself for lunch YES I said TIMING CHAIN! engine grenaded at 170,000 miles due to a timing chain failure. I have news for you in order to do a proper timing chain on a Benz you MUST pull the motor. Otherwise you get to run 2 chains before the engine has to be rebuilt and the second chain never runs as well as the first one did. I am sure folks are running more than 2 chains but the amount of error this puts into the cam and injection pump circuit is quite large making the engine harder and harder to get into proper timing.

A timing belt does not wear out the sprockets it rides on. They are quiter, lighter, dont require lubrication and are every bit as strong as a chain sometimes stronger. They apply a uniform pressure accross the face of the pulley reducing the likelyhood of a skipped tooth due to a larger contact area with the pulley.

Of course belts dont stretch out like chains do, again allowing the engine to run properly and in nearly perfect time or within spec over the full life of the belt. Some stretch does occur but no where near as much as a chain.

Owner costs of a belt are extremely low and require minimal time to replace compared to a properly done timing chain install.

Motor cycles have always used chains and work very well. How many FZR's or other sport bike make it to 150,000 miles or long enough to stretch out the chain? not many. Usually the bikes fail long before the chain either through owner abuse or the high probability that a car wipes it out. Of course the chain is only driving a single shaft i.e. the camshaft. The length of a chain required to drive a TDI setup would induce a very large amount of error in a short period of time of operation RELATIVE to a TDI, or 100,000 miles. This would require the owner to undertake a very expensive chain replacement to get the car running right again.

For me the belt is the hands down winner and a superior option over a sloppy chain set up.

DB
 

Drivbiwire

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2013 Passat TDI, Newmar Ventana 8.3L ISC 3945, 2016 E250 BT, 2000 Jetta TDI
I don't buy for a second the "noise" argument. It's got to be the money. The savings go in the auto makers pocket for sure. Lets not forget "job security" for dealerships with their "service specials".
Belt or chain I thought the only reason you would lunch a motor due to belt failure was because of valve clearance. That whole piston banging into the valve thing. Some motors do it, some don't. I jumped time on a Dodge 318 once. No big deal. Car ran fine after replacement.

Sprinter Van: 2.7 CDI chain driven cams.
Note the key word "CHAIN DRIVEN CAMS" there is no injection pump to be driven off the timing chain. The length of that chain would prevent any reasonable life out of the chain set up.

The money saved goes directly into the consumers pocket in terms of cost savings...not VW's. To be honest I want nothing to do with any motor that requires a minor overhaul every 150,000 miles diesel or not.

By the way whats the service life on the VR6 timing chain...120,000 miles? Merceds CDI 150,000 miles? Sorry I just cant see the cost savings.

DB
 

Frank M

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Work with me here and think long term ownership and maintenance costs:

How many wearable parts are in a timing belt set up?
-Belt
-Tensioner

How many wear able parts in a timing chain set up?
-Chain
-Crank gear
-Cam gear
-Injection pump gear
-Nylon Guides
-Tensioner

I see the arguement already...I never replaced the sprockets on any of my other vehicles...CORRECT! Try running a TDI with 1 tooth of slop on the cam because you did not replace all the chain sprockets and guides...BOOOM you just bought a head.
Okay you sold me on the TB. Now I am going out to get that Ferrari....
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
I have never heard of sprockets getting worn out on any engine with OHC's and timing chains. It MIGHT happen if the engine gets neglected after the chain has been making so much noise for so long that the owner cannot possibly ignore it except if they are deaf along with everyone else who rides in the vehicle!

You can't really compare timing chains for pushrod V8's with the arrangements used on OHC engines. Usually the chains are so short on pushrod V8's that there are no guides and there is no tensioner - hence the chain doesn't always make a lot of noise prior to failure. The OHC setup with the chains guided all the way around doesn't normally make much noise at all ... but it sure will if the chain goes sloppy!

Chain guides can wear out, especially if made of the wrong material, Toyota 22R's were known for this but not until at least 300,000 or 400,000 km ... I've never had to replace one on a bike engine, and the Toyota 2TZ's (later design) didn't have this issue.

An improperly engineered timing chain drive could have a failure, as could an improperly engineered timing belt drive. But a PROPERLY engineered timing chain drive should be good for the life of the engine.

Mercedes and BMW use timing chains for their current diesel engines. It works for them ...

Harleys do indeed use timing belts for the final drive. Check out how wide the belt is and how big the sprocket is compared to a chain on something else, and then compare the power output of a stock H-D pushrod engine to that of a GSXR1000 ...
 

Jetter_Sprinta

Veteran Member - TDIClub Contributor
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Drivbiwire, I have read your response and you make some very good points. I do, however, have some questions and comments.

Drivbiwire wrote:
"Of course belts don't stretch out like chains do, again allowing the engine to run properly and in nearly perfect time or within spec over the full life of the belt."

With modern day computer controls, would the motor be "allowed" to go out of time due to a stretched chain?

I do not understand what you mean by getting to do two chains. What part in a Benz motor cannot be replaced during a normal timing belt change?
Does this apply to ALL Benz engines? I get to contemplate pulling the motor out of my van? EEK!


Drivbiwire wrote:
"Owner costs of a belt are extremely low and require minimal time to replace compared to a properly done timing chain install."

Timing chain or belt, aren't they a similar amount of work? (My timing chain replacement experience is limited to older American iron.It probably shows) The labor is most always the clincher. What's cheaper two belts or one chain?

Drivbiwire wrote:
"By the way what's the service life on the VR6 timing chain...120,000 miles? Mercedes CDI 150,000 miles? Sorry I just can't see the cost savings."

If the life of the chain is 150K that means for all of those miles there is zero maintenance. If you can get away with two, that's 300K miles? That is quite a distance and usually a fair amount of time as well.

Was the chain failure on your fathers' car due to an improper install? Was it the first chain?
I have no big preference. They both have their pros and cons it seems. The main reason I like the chain is because a lot can happen in the amount of miles before a chain is due. Replacement could be a non- issue. When you shop for a "belt" car you always have to ask when was it done last or when is it due.
 

tdibugman

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Mar 16, 2001
Location
Forked River, NJ
well, since mercedes has been brought up..
this weekend, I'm getting an 83 300SD with 280K miles. Engine has never been opened. Timing chains are as quiet as anything. Properly engineered, and done with quality parts, I could see the chain outlasting the rest of the vehicle.
As far as costs, even if I was to replace the chain (it has no service interval) its about 1K bucks at the local Benz dealer. So, even if changed at, say 150K, I am almost three changes into my Beetle's belt replacemet - at a dealerships 695 dollar rate. So, I would have spent 2100 bucks for the Beetles belt. Now I see the cost savings....

and honestly, I LIKE having an engine that doesn't need an overhaul for over 150K miles. The 5 cylinder Benz is generally good for 500K before an overhaul. I'l go through two trannys before that.

And I still dont buy the noise thing... as I said both of our NEW, 4 cylinder Saabs have chains, and emit no noise.
 

T5TDI

Veteran Member
Joined
May 25, 1999
Location
Cornwall England
TDI
T5 Transporter 2.5
The new T5 Transporter/Eurovan (2.5 PD 174hp
) has no timing belt or chain. In fact it has no belts at all. No A/C belt, no PAS belt, no water pump or alternator belts. It's all done by gears. In fact, I've just ruined a perfectly good pair of trousers just talking about it.......

I want one now


P.S. It's not out here in the UK until July. Starting with the Multivan.
 

bowlerman

Veteran Member
Joined
Jul 31, 2001
Location
medford, NJ
TDI
2001 jetta tdi black
all this talk about timing belts and chains, what about gears!!! i have a 79 mack with gears and never touched timing, runs great. couple tractors with timing gears and never touched them either. timing gears i think are the best.
 
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