Timing Belt vs Timing Chain.

Theshedog

CJhaughey wrote: »

Chains don't stretch they wear out of tolerance, same with motorcycle drive chains they wear and get loose on the sprockets, they don't stretch.
Measure the side plates on a chain new and at replacement, is the side plate longer? answer is no it is not. The wear occurs in the pins and bushings.

+1

A mistake alot of people make. The wear causes people to think the chain is streching.

"The effect of wear on a roller chain is to increase the spacing of the links, causing the chain to grow longer. Note that this is not from any actual stretching of any metal, as too many engineers and mechanics intuitively believe, but is due to the effect of wear at the pivoting parts. It could be said that the roller chain loosens with wear"

Check this out (I know its bicycle chains but same principle applies)

http://www.sheldonbrown.com/chains.html

Slidey

I will say this.

According to Mercedes if the high pressure fuel pump on the CDI engine locks up it can stretch the chain.

However, I have seen several of these lock solid and the chains were all perfect afterwards.

CJhaughey

Theshedog wrote: »

+1

A mistake alot of people make. The wear causes people to think the chain is streching.

"The effect of wear on a roller chain is to increase the spacing of the links, causing the chain to grow longer. Note that this is not from any actual stretching of any metal, as too many engineers and mechanics intuitively believe, but is due to the effect of wear at the pivoting parts. It could be said that the roller chain loosens with wear"

Check this out (I know its bicycle chains but same principle applies)

http://www.sheldonbrown.com/chains.html

Its the exact point I have been making for the last half hour.
Chains wear out of tolerance, commonly known as stretching, but they don't actually stretch, if they did the sideplates would elongate, the amount of force it would take to stretch a chains sideplate is far beyond what a camshaft or crankshaft could provide without pulling the engine to bits.
But you can't make people understand that seemingly.:D

Mycroft H

CJhaughey wrote: »

Its the exact point I have been making for the last half hour.
Chains wear out of tolerance, commonly known as stretching, but they don't actually stretch, if they did the sideplates would elongate, the amount of force it would take to stretch a chains sideplate is far beyond what a camshaft or crankshaft could provide without pulling the engine to bits.
But you can't make people understand that seemingly.:D

Ahh i see, so they do stretch?

vw4life

chains and belts shoud be checked and replaced according to manufacturers recommendations and I've replaced as many chains as I've done belts

congo_90

mindless arguing aside. Lets see some evidence.
First poster to change a chain and measure it between a set of rivets on it compared to the same amount on a new one will be the best answer to this stretching v's non stretching.

Imo chains wear out and eventually fail. I'm not saying they will but can.

Slidey

The problem with that is measuring between the exact centres is not going to very easy.

It could be very easy to be one side of the top of the rivet.

If I get a chance I will get someone to find me the specs for the Mercedes chain which they ask you to measure when the high pressure pump seizes

alias no.9

Theshedog wrote: »

+1

A mistake alot of people make. The wear causes people to think the chain is streching.

"The effect of wear on a roller chain is to increase the spacing of the links, causing the chain to grow longer. Note that this is not from any actual stretching of any metal, as too many engineers and mechanics intuitively believe, but is due to the effect of wear at the pivoting parts. It could be said that the roller chain loosens with wear"

Check this out (I know its bicycle chains but same principle applies)

http://www.sheldonbrown.com/chains.html

It's the fact that the chain has extended or stretched that means that it can no longer fulfil its function because the timing willl be out. If you take a worn chain, pull it to the point of tension, measure the length, it will be longer than it was when new. If the overall length of the chain assembly increases, it has stretched, regardless of where the extension has come from. It's the basic difference between parts and assemblies, tolerances stack up on assemblies.

vw4life

Slidey wrote: »

The problem with that is measuring between the exact centres is not going to very easy.

It could be very easy to be one side of the top of the rivet.

If I get a chance I will get someone to find me the specs for the Mercedes chain which they ask you to measure when the high pressure pump seizes

I'll get you a new chain and a worn one t'moro from a '03 E200 if you want

Slidey

alias no.9 wrote: »

If the overall length of the chain assembly increases, it has stretched, regardless of where the extension has come from.

Trying not to be pedantic here, but it has rather lengthened than stretched.

As already said, the reason it has gotten longer is because the pins and bushes have worn in the links.

If the links themselves have become elongated from their original shape, then IMO, it would be correct to say it had stretched.

peasant

alias no.9 wrote: »

It's the fact that the chain has extended or stretched that means that it can no longer fulfil its function because the timing willl be out.

Close ...but still wrong

The chain in total may be longer, but the timing is still correct.
This is due to the fact that the individual links in the chain still slide into/onto the teeth of the sprocket in precicesly the same sequence as they did when the chain was shorter. (only with added rattle)

Only when the chain becomes so loose that the gaps and the teeth won't match up anymore will your timing go out (or rather the chain will break a tooth off, the chain will tear or jump off the sprocket)

PS: ... and I was trying to be pedantic

vw4life

peasant wrote: »

Close ...but still wrong

The chain in total may be longer, but the timing is still correct.

not on any ones I've done,timing is always off,sometimes the eng. mil comes on and stores a camshaft position sensor fault because the timing is that far out

peasant

vw4life wrote: »

not on any ones I've done,timing is always off,sometimes the eng. mil comes on and stores a camshaft position sensor fault because the timing is that far out

Every day is a school day, or so it seems ...

Wouldn't have thought that that would be the case

maidhc

both chains and belts are imperfect.

Timing gears FTW.

beachlife

peasant wrote: »

Close ...but still wrong

The chain in total may be longer, but the timing is still correct.
This is due to the fact that the individual links in the chain still slide into/onto the teeth of the sprocket in precicesly the same sequence as they did when the chain was shorter. (only with added rattle)

Only when the chain becomes so loose that the gaps and the teeth won't match up anymore will your timing go out (or rather the chain will break a tooth off, the chain will tear or jump off the sprocket)

PS: ... and I was trying to be pedantic

Wrong!!!! The chain will be longer,why? because of the wear/stretch(what ever you want to call it,basically a "worn" chain IS longer than a new chain)and how will it be longer? the distance on each and every pin will be slightly longer so the camshaft/crankshaft WILL be off. Think if a camshaft has it's timing mark at 12 o'clock and the crank shaft has it's timing mark at 12 also and the tight side(no the tensioner side) of the chain has 80 links between them if the chain get's longer now when you have the same 80 links between them the marks won't line up.
I've seen it many times.OLd honda 50's used to be half a link out all the time and still run(badly)

Slidey

vw4life wrote: »

not on any ones I've done,timing is always off,sometimes the eng. mil comes on and stores a camshaft position sensor fault because the timing is that far out

Sorry P, I gotta side with vw4life.

If the pins are worn the chain will have gotten longer.

Now if the distance between pin a and pin b 25 links away is normally 200mm and all the links are worn then the distance will have increased.

The result of this is that the chain length between the crank pulley and the cam has increased and now the cam timing will be slightly retarded.

alias no.9

peasant wrote: »

Close ...but still wrong

The chain in total may be longer, but the timing is still correct.
This is due to the fact that the individual links in the chain still slide into/onto the teeth of the sprocket in precicesly the same sequence as they did when the chain was shorter. (only with added rattle)

Only when the chain becomes so loose that the gaps and the teeth won't match up anymore will your timing go out (or rather the chain will break a tooth off, the chain will tear or jump off the sprocket)

PS: ... and I was trying to be pedantic

Yes, you're correct. It's late in the day, first day back in work after a long break.

beachlife

I also feel that newer car/bikes have less of a tolerance for mis-timing than the older machines.actually I know that they have her's the proof of worn/strected timing chain affecting timing.
Enjoy.

alias no.9

beachlife wrote: »

I also feel that newer car/bikes have less of a tolerance for mis-timing than the older machines.actually I know that they have her's the proof of worn/strected timing chain affecting timing.
Enjoy.

That's a good illustration of what's happening. A lot of us, me included, have been thinking about this one too simplistically, the system is limited both by the ratio of teeth on the sprockets as well as the length of the chain / pitch of the links.
On average, the crankshaft and camshaft have to stay in in synch, two revs of the crankshaft to every rev of the cam shaft until it skips a tooth which I think was Pesants point.
With a stretched/worn chain, you get a tooth by tooth retardation of the camshaft but as long as each link of the chain is mating with the correct tooth on each sprocket it will eventually be forced to catch up or reset after a given number of teeth in order for the chain to continue to mesh with the sprocket.
As the wear/stretching gets worse, the number of teeth between resets will increase in theroy until it would eventually skip a tooth.

beachlife

Sorry Alias there is no catch up or reset. the tooth on the gear/sprocket simply meshes with the roller of the chain until such time that the tooth the hits a point on the roller that is over centre and jump forward(skips a tooth)or snaps (forces the chain away to sit on the tooth)the chain. the point I am making is that the timing on any modern car would be so far off at this stage that the car will not be running.

Slidey

beachlife wrote: »

Sorry Alias there is no catch up or reset. the tooth on the gear/sprocket simply meshes with the roller of the chain until such time that the tooth the hits a point on the roller that is over centre and jump forward(skips a tooth)or snaps (forces the chain away to sit on the tooth)the chain. the point I am making is that the timing on any modern car would be so far off at this stage that the car will not be running.

Exactly. If there is an oil fed tensioner, this will do its best to keep the chain tight and avoid the chain jumping a tooth.

However, once there is wear in the chain it will retard the timing. This will progressively get worse 'til either the engine won't start due to timing issues or the chain breaks/skips a tooth

unkel

beachlife wrote: »

skips a tooth

So that's key then? The lengthening of the chain (because of wear) causes the skip, slowing the sprocket and thus retarding the timing?

I know from experience that skipping is exactly what happens when the chain is worn...





...on a pushbike

peasant

beachlife wrote: »

the point I am making is that the timing on any modern car would be so far off at this stage that the car will not be running.

so chains aren't really the ideal solution for newer engines either...certainly not as lifetime-maintenance-free as folklore has it.

Slidey

unkel wrote: »

So that's key then? The lengthening of the chain (because of wear) causes the skip, slowing the sprocket and thus retarding the timing?

TBH, once a chain skips a tooth it is FUBAR'd and if it did it once it will probably do it enough times til the piston finally does the durty deed with a valve (or 3)

beachlife

No timing belts are much better for modern engines.The folklore came about because in the "old" day's the timing chain on the fiesta would keep going till it came thru the housing!!! why?? because it was points and would run with the timing a mile off and no emissions test to speak of!!
But on modern car the belt is the way to go,ford got it right with the focus 100,000 mile or ten years!! now thats a good interval.good strong belt too for the size of the engine(1.4/1.6),just compare it with a punto belt(1.2)

Slidey

peasant wrote: »

so chains aren't really the ideal solution for newer engines either...certainly not as lifetime-maintenance-free as folklore has it.

Well, that is a debate that could rage on for a long time.

I have seen many old Sprinter (412's, same engine that is in the Korando and old SSangyongs) engines on 400k with original chains and very little rattle in them.

As said earlier the Nissan in the Almera is a disaster in comparison.

If the Sprinter above had a belt it would have been changed probably 5/6 times at that stage along with tensioners and idlers.

If it cost effective - well thats the debate really...

Personally I would prefer the belt, especially if it was easy to access and didn't run the water pump. That in my mind is not a great idea.

congo_90

Slidey wrote: »

Well, that is a debate that could rage on for a long time.

I have seen many old Sprinter (412's, same engine that is in the Korando and old SSangyongs) engines on 400k with original chains and very little rattle in them.

As said earlier the Nissan in the Almera is a disaster in comparison.

If the Sprinter above had a belt it would have been changed probably 5/6 times at that stage along with tensioners and idlers.

If it cost effective - well thats the debate really...

Personally I would prefer the belt, especially if it was easy to access and didn't run the water pump. That in my mind is not a great idea.

She drives an Almera and I do from time to time. Is it across the entire range or specific year?

vw4life

Slidey wrote: »

Well, that is a debate that could rage on for a long time.

I have seen many old Sprinter (412's, same engine that is in the Korando and old SSangyongs) engines on 400k with original chains and very little rattle in them.

As said earlier the Nissan in the Almera is a disaster in comparison.

If the Sprinter above had a belt it would have been changed probably 5/6 times at that stage along with tensioners and idlers.

If it cost effective - well thats the debate really...

Personally I would prefer the belt, especially if it was easy to access and didn't run the water pump. That in my mind is not a great idea.

in general the Merc double roller chain lasts a long time 'cause it was over engineered,but unfortunatly the single roller chain has made a major comeback in the 1.8 petrol engine and its pure crap on the early ones

beachlife

you just said it yourself there old sprinter.The new common rail diesels wouldn't run with a worn chain because there set up more like the petrols with the cam/crank sensors and there synch problems

Slidey

congo_90 wrote: »

She drives an Almera and I do from time to time. Is it across the entire range or specific year?

That I don't know. It was something I was told but only retained some of the info!