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What About A Timing Belt?
- Thread starter ReycleBill
- Start date
Hi RecycleBill / All:
This is a very interesting thread - thanks for raising it Bill. If I may, I'd like to contribute a few thoughts....
Actually, many modern vehicles are moving away from timing belts and to timing chains (several have been named by others but I know that my 1994 NA Miata had a belt but my 2006 NC Miata has a chain - ahhhh....no worries and no servicing beyond oil changes.
Having said that, some OEMs are having major headaches with very complex timing chain drives (Ford 3.5 litre ecoboost, BMW N20 four cylinder, and many Audi models) - so chains ain't perfect. The problems seem to come when the chain has to drive more than just a couple of camshafts - the thing gets too long with too many wraps around chainwheels and positive and negative tension conditions around the mechanical circuit.
Yes - the typical service interval on older belt drives was 100,000 km, at least here in Canada, and not 100,000 miles (that would be about 162,000 km - and you'd be well into very risky territory at that milage).
Many older lower-compression engines are "non-interference" designs and so a broken timing belt or chain means a tow and a fairly simple installation of a new belt/chain, but some engines (generally the higher performance models) are what is known as "interference engines" which means that the valves will collide with the piston crown - or with each other - if the camshaft timing gets too far out of whack.
I must admit that I hadn't heard of the belt-in-oil design. As first blush, it sounds OK but I'd want to see some long-term durability data on the belts with different grades of oil.
Finally, I agree with Gary: there is little difference in efficiency between a well lubed chain running at the correct tension and a properly tensioned belt. I do recall when Harley went to toothed final drive belts, they claimed some milage bonus but I have never seen any data to back that up.
Pete
This is a very interesting thread - thanks for raising it Bill. If I may, I'd like to contribute a few thoughts....
Actually, many modern vehicles are moving away from timing belts and to timing chains (several have been named by others but I know that my 1994 NA Miata had a belt but my 2006 NC Miata has a chain - ahhhh....no worries and no servicing beyond oil changes.
Having said that, some OEMs are having major headaches with very complex timing chain drives (Ford 3.5 litre ecoboost, BMW N20 four cylinder, and many Audi models) - so chains ain't perfect. The problems seem to come when the chain has to drive more than just a couple of camshafts - the thing gets too long with too many wraps around chainwheels and positive and negative tension conditions around the mechanical circuit.
Yes - the typical service interval on older belt drives was 100,000 km, at least here in Canada, and not 100,000 miles (that would be about 162,000 km - and you'd be well into very risky territory at that milage).
Many older lower-compression engines are "non-interference" designs and so a broken timing belt or chain means a tow and a fairly simple installation of a new belt/chain, but some engines (generally the higher performance models) are what is known as "interference engines" which means that the valves will collide with the piston crown - or with each other - if the camshaft timing gets too far out of whack.
I must admit that I hadn't heard of the belt-in-oil design. As first blush, it sounds OK but I'd want to see some long-term durability data on the belts with different grades of oil.
Finally, I agree with Gary: there is little difference in efficiency between a well lubed chain running at the correct tension and a properly tensioned belt. I do recall when Harley went to toothed final drive belts, they claimed some milage bonus but I have never seen any data to back that up.
Pete
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And cutting out a few cheese burgers or beers might save a bit too!Running with 1 gallin in a 3 gallon tank saves 14 pounds.
Well, I guess the no speed limit Autobahn may have influenced the decisions regarding service intervals. And generally, BMW engines had higher output per liter than most other cars. Like the 150 hp 2.3 liter and the 170 hp 2.5 liter inline 6 engines. And they were definitely interference engines AS well. And a belt replacement could be considered a cheap and quick insurance against a wrecked engine.
Dont know much of automobiles but it was not long ago I heard of BMW cars having problems with tensioners being of a poor design
Those service intervals ..some people skipped Or did not have time do it .. .since it is a well know fact or was that if you want to drive cheap don't go BMW
Would not be surprised if a service is into the 4 digits US $ or close
And then the rattle from the tensioner was there .. And these were fairly new cars .. Again I Dont know much but this was an fairly new BMW that the story teller had bought cheap to do the repair.
I am skeptical of the service intervals and designs .. Demanding shop service ..that is at times more expensive than I ever have bought a motorcycle for
The lesser Rubber or Polymer or Plastic there is in a mechanical design it is all in all -- better in my View.
Some places one have to have it and costs is a factor ( Walnut wood dashboard not seen anymore ) Seals .and so .But if you ask me the design with a cam belt is to build in a risk in an engine
Sure lawyer madam Nice Wont.. even change a tire and do all the service according to the book having the grease monkey do it.
Just picking up the bill
Its the same with electronics also a risk .that manifests itself after some years that the first lady buyer dont know or care about
But there are cars being scrapped because electrical faults .And in the context of Sustainability it does not sound right to me.
We have Motorcycles that is 40 years old sure thee are Camchain problems but not close to what I have heard about belts
One of my friends that got a broken belt rem smashed engine got it in his face after pointing at the service intervals
was it second at 180 000 km
Yes but there is some spread it is not exactly so
He was far from 18000 Km when the belt broke and he ended up with the bill
" IS the car serviced at the makers Shop " Skoda in this case No off course not
And then he pretty much Heard ------------------- PPPppppppprr.....tttttttttttttttt
Those service intervals ..some people skipped Or did not have time do it .. .since it is a well know fact or was that if you want to drive cheap don't go BMW
Would not be surprised if a service is into the 4 digits US $ or close
And then the rattle from the tensioner was there .. And these were fairly new cars .. Again I Dont know much but this was an fairly new BMW that the story teller had bought cheap to do the repair.
I am skeptical of the service intervals and designs .. Demanding shop service ..that is at times more expensive than I ever have bought a motorcycle for
The lesser Rubber or Polymer or Plastic there is in a mechanical design it is all in all -- better in my View.
Some places one have to have it and costs is a factor ( Walnut wood dashboard not seen anymore ) Seals .and so .But if you ask me the design with a cam belt is to build in a risk in an engine
Sure lawyer madam Nice Wont.. even change a tire and do all the service according to the book having the grease monkey do it.
Just picking up the bill
Its the same with electronics also a risk .that manifests itself after some years that the first lady buyer dont know or care about
But there are cars being scrapped because electrical faults .And in the context of Sustainability it does not sound right to me.
We have Motorcycles that is 40 years old sure thee are Camchain problems but not close to what I have heard about belts
One of my friends that got a broken belt rem smashed engine got it in his face after pointing at the service intervals
was it second at 180 000 km
Yes but there is some spread it is not exactly so
He was far from 18000 Km when the belt broke and he ended up with the bill
" IS the car serviced at the makers Shop " Skoda in this case No off course not
And then he pretty much Heard ------------------- PPPppppppprr.....tttttttttttttttt
Dave Raynor in Oz
There is on thing to which I can definitely testify:
1) the XS650 timing chain drive system is a very fault tolerant design.
My ‘76 XS650C (the horrifying Lucille
) suffered a total failure of the front timing chain tensioner (the entire plastic guide fell off the aluminium shoe) and I rode her home nearly 60 miles from Lakeview’s country estate at 55 MPH - with nothing more than a rhythmic rapping of the chain on the aluminium shoe. She started and ran fine w/o any problems.
2) the timing chain is extremely unlikely to ever actually break.
So, for all her faults, this old gal will get ya home.
Pete
1) the XS650 timing chain drive system is a very fault tolerant design.
My ‘76 XS650C (the horrifying Lucille
) suffered a total failure of the front timing chain tensioner (the entire plastic guide fell off the aluminium shoe) and I rode her home nearly 60 miles from Lakeview’s country estate at 55 MPH - with nothing more than a rhythmic rapping of the chain on the aluminium shoe. She started and ran fine w/o any problems.2) the timing chain is extremely unlikely to ever actually break.
So, for all her faults, this old gal will get ya home.
Pete
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Some people do stuff because they can. I can't and I won't. So there.There is on thing to which I can definitely testify:
1) the XS650 timing chain drive system is a very fault tolerant design.
My ‘76 XS650C (the horrifying Lucille
2) the timing chain is extremely unlikely to ever actually break.
So, for all her faults, this old gal will get ya home.
Pete
Pete, I agree and trust this old machine probably better than I trust a new one.
To be fair the failures on front guides are most likely age related. Would anyone think ill of a 40+ year old tire failing? It's rutine to need to replace a lot of the rubber parts on a bike when when bringing 1 back from the grave. Were front guides a problem back in the bikes day? 70s-80s. The chain stretching is a product of wear and/or lack of maintenance. Could the design be better? By today's standards yes! But all in all it has stood the test of time. If you research this forum I think you will only find 1 instance of a cam chain breaking. If I remember right he had 70+ thousands of miles on it.
Yup, but I didn’t have a trailer and frankly, the rapping noise really wasn’t that bad.
It seems you have some mixed up info on BMW cars, and potential issues. I have owned BMW cars of 3 different generations.
1981 518 (E12) M10 engine, inline 4, sohc, duplex chain. No issues for 300 000km
1986 320i (E30) M20 engine, inline 6, sohc, timing belt, manual tensioner. Replaced every 60 000 km. No issues whatsoever fir 285 000 km.
2003 316i (E46) N42 engine, inline 4, dohc, 16 valve, dual vanos, valvetronic, 2 balancer shafts for secondary imbalance. Single row camchain with springloaded/ hydraulic tensioner. Stopped running at around 230 000 km due to stretched timing chain (ECU received camshaft and crankshaft position data outside of the tolerance) 2 different shops quoted a bit over $2000 in labor+$600 in parts. In the end I fitted new chain, crankshaft sprocket, chain sliders, chain tensioner myself. And learned my way around a modern car engine at the same time.
Point of my story is, the M20 engine with a timing belt was more reliable, cheaper to maintain, and durable. As long as the belts were replaced at the set intervals.
