OVERKILL
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If shortening the OCI length reduces chain wear (which appears to be GM's bandaid), doesn't that throw the whole theory of long OCI's having lower wear out the window?
Oil Choice for Lowest Wear On Engine Timing Chain?
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Originally Posted By: OVERKILL
If shortening the OCI length reduces chain wear (which appears to be GM's bandaid), doesn't that throw the whole theory of long OCI's having lower wear out the window?
If you trust GM's judgement it does. I no trust them. Keep in mind some of the worst rates of failures have occurred in model years of this GM HFV6 that did not have direction injection DI. GM says long OCI with DI is bad, yet failures were often most frequent in their non-DI versions of this same engine.
Granted, fuel dilution issues exist with DI engines, and that must be watched.
More to your point though, there are some pretty good wear studies that show that fresh oil actually causes higher wear rates. See original first post in this thread for references.
If shortening the OCI length reduces chain wear (which appears to be GM's bandaid), doesn't that throw the whole theory of long OCI's having lower wear out the window?
If you trust GM's judgement it does. I no trust them. Keep in mind some of the worst rates of failures have occurred in model years of this GM HFV6 that did not have direction injection DI. GM says long OCI with DI is bad, yet failures were often most frequent in their non-DI versions of this same engine.
Granted, fuel dilution issues exist with DI engines, and that must be watched.
More to your point though, there are some pretty good wear studies that show that fresh oil actually causes higher wear rates. See original first post in this thread for references.
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OVERKILL
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Originally Posted By: FetchFar
More to your point though, there are some pretty good wear studies that show that fresh oil actually causes higher wear rates. See original first post in this thread for references.
That's exactly what I'm digging at. There are a number of studies that have been posted on here that point to that, yet GM appears to be trying to argue the opposite
Which either means the topic has a few different angles that we haven't looked at (IE wear in CERTAIN AREAS decreases as the oil ages... but this does not apply to every component.... like say the timing chain....) or GM is completely out to lunch. Which then begs the question as to why they'd bother and not just recall the engines with the defective chains?
More to your point though, there are some pretty good wear studies that show that fresh oil actually causes higher wear rates. See original first post in this thread for references.
That's exactly what I'm digging at. There are a number of studies that have been posted on here that point to that, yet GM appears to be trying to argue the opposite
Which either means the topic has a few different angles that we haven't looked at (IE wear in CERTAIN AREAS decreases as the oil ages... but this does not apply to every component.... like say the timing chain....) or GM is completely out to lunch. Which then begs the question as to why they'd bother and not just recall the engines with the defective chains?
Originally Posted By: OVERKILL
Which either means the topic has a few different angles that we haven't looked at (IE wear in CERTAIN AREAS decreases as the oil ages... but this does not apply to every component.... like say the timing chain....) or GM is completely out to lunch. Which then begs the question as to why they'd bother and not just recall the engines with the defective chains?
Agreed, and its why my eyes opened wide when another poster cited that GF-6 will add a test for chain wear. Up to now its been assumed that whats good for the cam is good for the chain (goose-gander thing i guess LOL).
Which either means the topic has a few different angles that we haven't looked at (IE wear in CERTAIN AREAS decreases as the oil ages... but this does not apply to every component.... like say the timing chain....) or GM is completely out to lunch. Which then begs the question as to why they'd bother and not just recall the engines with the defective chains?
Agreed, and its why my eyes opened wide when another poster cited that GF-6 will add a test for chain wear. Up to now its been assumed that whats good for the cam is good for the chain (goose-gander thing i guess LOL).
OVERKILL
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Originally Posted By: FetchFar
Originally Posted By: OVERKILL
Which either means the topic has a few different angles that we haven't looked at (IE wear in CERTAIN AREAS decreases as the oil ages... but this does not apply to every component.... like say the timing chain....) or GM is completely out to lunch. Which then begs the question as to why they'd bother and not just recall the engines with the defective chains?
Agreed, and its why my eyes opened wide when another poster cited that GF-6 will add a test for chain wear. Up to now its been assumed that whats good for the cam is good for the chain (goose-gander thing i guess LOL).
Yup, I noticed that too (and replied to it). I was also quite intrigued. I wonder if that's currently part of certain OEM's testing and approval regimes? Like perhaps Mercedes?
Originally Posted By: OVERKILL
Which either means the topic has a few different angles that we haven't looked at (IE wear in CERTAIN AREAS decreases as the oil ages... but this does not apply to every component.... like say the timing chain....) or GM is completely out to lunch. Which then begs the question as to why they'd bother and not just recall the engines with the defective chains?
Agreed, and its why my eyes opened wide when another poster cited that GF-6 will add a test for chain wear. Up to now its been assumed that whats good for the cam is good for the chain (goose-gander thing i guess LOL).
Yup, I noticed that too (and replied to it). I was also quite intrigued. I wonder if that's currently part of certain OEM's testing and approval regimes? Like perhaps Mercedes?
I know one thing, this thread had given me a whole new appreciation for zinc, boron, moly, calcium and the task oil formulators face when trying for dexos1 and/or VW 502/505 wear standards. Not easy. I guess it can't be as easy as just dumping in Lubro Moly MoS2 additive anyway, darn it.
If we had access to UOAs of several engines that had failed timing chains, I wonder if they would show a high silica (hard tiny particles) count. Oil and air filters don't get rid of tiny boulders in the 0.1 to 20 micron range after all. Operating in dusty environments has generally been bad for wear.
The new oil wear as pointed out to me in another thread by friendly jacek, plus MoS2 being the end result of soluble moly, have me "preconditioning" my oil for want of a better word with a small amount of liquimoly at oil changes these days...A tine serves two cars, 12L combined change...makes me feel better about new oil.
Originally Posted By: Shannow
The new oil wear as pointed out to me in another thread by friendly jacek, plus MoS2 being the end result of soluble moly, have me "preconditioning" my oil for want of a better word with a small amount of liquimoly at oil changes these days...A tine serves two cars, 12L combined change...makes me feel better about new oil.
How much are you pre-conditioning each litre, or how much would you add to a quart for us USA members? Thanks
The new oil wear as pointed out to me in another thread by friendly jacek, plus MoS2 being the end result of soluble moly, have me "preconditioning" my oil for want of a better word with a small amount of liquimoly at oil changes these days...A tine serves two cars, 12L combined change...makes me feel better about new oil.
How much are you pre-conditioning each litre, or how much would you add to a quart for us USA members? Thanks
Note, "preconditioning" is only my halfRsed concept of getting some disulfide in the system rather than waiting for heat and pressure to get it happening...no warranty implied or given, nor any actual science.
Nissan takes about 7 litres and gets a "large" half bottle. Caprice holds about 4.5 and gets the smaller "half". The mower gets what hasn't drained out of the bottle, with it's oil change used to rinse the bottle.
Nissan takes about 7 litres and gets a "large" half bottle. Caprice holds about 4.5 and gets the smaller "half". The mower gets what hasn't drained out of the bottle, with it's oil change used to rinse the bottle.
Originally Posted By: Shannow
The new oil wear as pointed out to me in another thread by friendly jacek, plus MoS2 being the end result of soluble moly, have me "preconditioning" my oil for want of a better word with a small amount of liquimoly at oil changes these days...
Now, combine that with two quarts of TGMO (or would that be 20w-50 in Australia), and we have a Shannow blend.
@OVERKILL: I'm not sure what Chevy's reason for shortening the OCI would be. Is it actually accomplishing something, or does it make it look like they're trying? Timing chain wear notably was near the bottom of the list of worries in the taxi fleet with small block Chevy motors, and those weren't short OCIs. Fuel dilution or tiny little abrasives have been suggested in the thread, and those are as good an explanation as any, aside from manufacturing defect in the first place.
After all, nothing did more to propagate the notion of cam wear with low ZDDP oils than did the Chevy small block years back.
Thanks to Chevy's contribution, that whole matter took on a life all its own.
The new oil wear as pointed out to me in another thread by friendly jacek, plus MoS2 being the end result of soluble moly, have me "preconditioning" my oil for want of a better word with a small amount of liquimoly at oil changes these days...
Now, combine that with two quarts of TGMO (or would that be 20w-50 in Australia), and we have a Shannow blend.
@OVERKILL: I'm not sure what Chevy's reason for shortening the OCI would be. Is it actually accomplishing something, or does it make it look like they're trying? Timing chain wear notably was near the bottom of the list of worries in the taxi fleet with small block Chevy motors, and those weren't short OCIs. Fuel dilution or tiny little abrasives have been suggested in the thread, and those are as good an explanation as any, aside from manufacturing defect in the first place.
After all, nothing did more to propagate the notion of cam wear with low ZDDP oils than did the Chevy small block years back.
Originally Posted By: Shannow
Note, "preconditioning" is only my halfRsed concept of getting some disulfide in the system rather than waiting for heat and pressure to get it happening...no warranty implied or given, nor any actual science.
Nissan takes about 7 litres and gets a "large" half bottle. Caprice holds about 4.5 and gets the smaller "half". The mower gets what hasn't drained out of the bottle, with it's oil change used to rinse the bottle.
That's about what I'm doing, after an initial treatment of a whole bottle. The same disclaimers apply.
Note, "preconditioning" is only my halfRsed concept of getting some disulfide in the system rather than waiting for heat and pressure to get it happening...no warranty implied or given, nor any actual science.
Nissan takes about 7 litres and gets a "large" half bottle. Caprice holds about 4.5 and gets the smaller "half". The mower gets what hasn't drained out of the bottle, with it's oil change used to rinse the bottle.
That's about what I'm doing, after an initial treatment of a whole bottle. The same disclaimers apply.
"Up to now its been assumed that whats good for the cam is good for the chain"
Nope...ILSAC GF-5 doesn't give a goose-gander about wear performance. This is probably why automakers are bringing out their own oils...And the GM Dexos spec. See here.....
http://origin-qps.onstreammedia.com/orig...p/pc/index.html
Nope...ILSAC GF-5 doesn't give a goose-gander about wear performance. This is probably why automakers are bringing out their own oils...And the GM Dexos spec. See here.....
http://origin-qps.onstreammedia.com/orig...p/pc/index.html
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Originally Posted By: martinq
ILSAC to Add Timing Chain Wear Test to GF-6
http://www.pceo.com/node/262
"The one component that suffers the most from accelerated wear in GDI and GDI-T engines is the metal timing chain, which drives the camshaft(s) off of the crankshaft. Excessive wear can cause the check engine light to illuminate and could result in very expensive internal engine hardware repairs. Excess wear is evident in chain elongation which can disturb valve timing leading to degraded performance and higher engine out emissions. Researchers are not yet sure about the exact wear mechanism—it could be abrasive wear from carbon particles suspended in the lube oil or an interaction between carbon particles and the lubricant or both."
This point is very interesting in that (if true) it sheds some light on exactly why this problem is more prone to D.I. engines with timing chains as opposed to standard port injected engines.
So in appears that the increased "soot" loading of the oil in a D.I. engine affects the wear rate on the timing chain (could be almost similar to diesel). So if that's true, then GM's new shortened change intervals should help ad they remove the hard carbon particles causing the wear more frequently.
If they wanted to keep the longer change intervals, then it looks like they would have had to design a beefier chain, increase oil capacity, spec a more diesel-like oil, and keep temps / fuel dilution in check throughout the oci. Also, oil level likely plays a big role because as oil gets burned off, the concentration of hard carbon soot particles greatly increases per unit volume of oil.
Very interesting discussion!
ILSAC to Add Timing Chain Wear Test to GF-6
http://www.pceo.com/node/262
"The one component that suffers the most from accelerated wear in GDI and GDI-T engines is the metal timing chain, which drives the camshaft(s) off of the crankshaft. Excessive wear can cause the check engine light to illuminate and could result in very expensive internal engine hardware repairs. Excess wear is evident in chain elongation which can disturb valve timing leading to degraded performance and higher engine out emissions. Researchers are not yet sure about the exact wear mechanism—it could be abrasive wear from carbon particles suspended in the lube oil or an interaction between carbon particles and the lubricant or both."
This point is very interesting in that (if true) it sheds some light on exactly why this problem is more prone to D.I. engines with timing chains as opposed to standard port injected engines.
So in appears that the increased "soot" loading of the oil in a D.I. engine affects the wear rate on the timing chain (could be almost similar to diesel). So if that's true, then GM's new shortened change intervals should help ad they remove the hard carbon particles causing the wear more frequently.
If they wanted to keep the longer change intervals, then it looks like they would have had to design a beefier chain, increase oil capacity, spec a more diesel-like oil, and keep temps / fuel dilution in check throughout the oci. Also, oil level likely plays a big role because as oil gets burned off, the concentration of hard carbon soot particles greatly increases per unit volume of oil.
Very interesting discussion!
Originally Posted By: Lex94
"Up to now its been assumed that whats good for the cam is good for the chain"
Nope...ILSAC GF-5 doesn't give a goose-gander about wear performance. This is probably why automakers are bringing out their own oils...And the GM Dexos spec. See here.....
http://origin-qps.onstreammedia.com/orig...p/pc/index.html
The good-for-cam, good-for-chain-assumption comment was actually simply in reference to the fact that the cams get their own test in SN/GF-5, but no chain test....yet, as GF-6 might add this test(not finalized). Anybody know if MB 229.5 or VW 505 or Porsche C30 has a current timing chain wear test?
"Up to now its been assumed that whats good for the cam is good for the chain"
Nope...ILSAC GF-5 doesn't give a goose-gander about wear performance. This is probably why automakers are bringing out their own oils...And the GM Dexos spec. See here.....
http://origin-qps.onstreammedia.com/orig...p/pc/index.html
The good-for-cam, good-for-chain-assumption comment was actually simply in reference to the fact that the cams get their own test in SN/GF-5, but no chain test....yet, as GF-6 might add this test(not finalized). Anybody know if MB 229.5 or VW 505 or Porsche C30 has a current timing chain wear test?
Originally Posted By: FetchFar
Anybody know if MB 229.5 or VW 505 or Porsche C30 has a current timing chain wear test?
I have some older documentation that does not list any kind of chain wear test for MB 229.5 or VW 505... There are lots of other tests and limits, but nothing that I can directly attribute to the chain. VW lists "valvetrain wear", but I'd tend to think that involves cams / buckets / etc and not necessarily the chain.
Things may have changed since those specifications were originally introduced, but I don't have any more recent information. Also, I don't have anything on the Porsche A30 / C30 testing.
Anybody know if MB 229.5 or VW 505 or Porsche C30 has a current timing chain wear test?
I have some older documentation that does not list any kind of chain wear test for MB 229.5 or VW 505... There are lots of other tests and limits, but nothing that I can directly attribute to the chain. VW lists "valvetrain wear", but I'd tend to think that involves cams / buckets / etc and not necessarily the chain.
Things may have changed since those specifications were originally introduced, but I don't have any more recent information. Also, I don't have anything on the Porsche A30 / C30 testing.
Originally Posted By: FetchFar
Wow, fantastic tech discussion. I can't thank enough. OK, based on jrustles comments above, does that make one think a higher-viscosity or a lower visc oil will improve things, as GM currently specifies a 30. ? Does a pure PAO synthetic strengthen boundary, which would mean I'd go for Amsoil signature or German Castrol me supposes.
I still think if I could just get a little moly into those pin/bushing/link interfaces then abrading goes down..... Wish I had proof that would work.
Well, there are two types of chain failures, excessive guide wear and actual chain stretching, sometimes both!
Moly could be great for treating "EP" wear resulting from the link-pin interface. Here's my brutal illustration of my understanding of chain stretching:
The 'EP' zones that must withstand repeated hammering are in the red areas which represent the increased clearance from wear
The culprits in my view:
a failure of lubrication - insufficient viscosity, additive chemistry due to any number of reasons
and/or
design - chain links too narrow accelerating pin hole wear, too light of a chain matched to too sprung a valvetrain etc
and/or
aftertreatment - improper nitriding or other hardening process (common)
and/or
metallurgy - improper alloy (rare)
Which chain do you think will wear quicker?
Originally Posted By: Shannow
Originally Posted By: jrustles
Boundary lubrication may not be sufficient for chains, especially against non-metallic (nylon) guides where additives don't quite work as they do on metal.
Wondering how the impregnability of polymers goes at creating (for want of a better word) sandpaper in either guide, or pulley.
White metal bearings were chosen to allow small particles to be pressed into the material, and then be clear of the hydrodynamically lubricated parts...impregnation and boundary lubes probably not the bet idea, even if nylon is a good bearing material on it's own.
That's a good point, so wear from abrasives against the polymer guide really shouldn't be an issue as the impregnability helps it in that regard, or would abrasives not fully bed into the polymer guide creating the effect you describe?.
Wow, fantastic tech discussion. I can't thank enough. OK, based on jrustles comments above, does that make one think a higher-viscosity or a lower visc oil will improve things, as GM currently specifies a 30. ? Does a pure PAO synthetic strengthen boundary, which would mean I'd go for Amsoil signature or German Castrol me supposes.
I still think if I could just get a little moly into those pin/bushing/link interfaces then abrading goes down..... Wish I had proof that would work.
Well, there are two types of chain failures, excessive guide wear and actual chain stretching, sometimes both!
Moly could be great for treating "EP" wear resulting from the link-pin interface. Here's my brutal illustration of my understanding of chain stretching:
The 'EP' zones that must withstand repeated hammering are in the red areas which represent the increased clearance from wear
The culprits in my view:
a failure of lubrication - insufficient viscosity, additive chemistry due to any number of reasons
and/or
design - chain links too narrow accelerating pin hole wear, too light of a chain matched to too sprung a valvetrain etc
and/or
aftertreatment - improper nitriding or other hardening process (common)
and/or
metallurgy - improper alloy (rare)
Which chain do you think will wear quicker?
Originally Posted By: Shannow
Originally Posted By: jrustles
Boundary lubrication may not be sufficient for chains, especially against non-metallic (nylon) guides where additives don't quite work as they do on metal.
Wondering how the impregnability of polymers goes at creating (for want of a better word) sandpaper in either guide, or pulley.
White metal bearings were chosen to allow small particles to be pressed into the material, and then be clear of the hydrodynamically lubricated parts...impregnation and boundary lubes probably not the bet idea, even if nylon is a good bearing material on it's own.
That's a good point, so wear from abrasives against the polymer guide really shouldn't be an issue as the impregnability helps it in that regard, or would abrasives not fully bed into the polymer guide creating the effect you describe?.
One possible problem could be inadequate flow to the chain. Might explain why the GM High Feature V6 chains have had higher failure rates. .... Does anybody know how these chains are oiled? I think I see a squirt nozzle next to the chain in the picture at this link: LLT v6 engine cutaway, zoom in to see possible oil nozzle...
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Originally Posted By: Garak
@OVERKILL: I'm not sure what Chevy's reason for shortening the OCI would be. Is it actually accomplishing something, or does it make it look like they're trying? Timing chain wear notably was near the bottom of the list of worries in the taxi fleet with small block Chevy motors, and those weren't short OCIs. Fuel dilution or tiny little abrasives have been suggested in the thread, and those are as good an explanation as any, aside from manufacturing defect in the first place.
SBC timing chains are a totally different animal, way shorter, way beefier, far fewer links to cumulatively add length from wear, which they were again more resistant to. In an already somewhat challenging aspect of modern engine design (the longest, lightest, lowest friction chain game), it doesn't help that OHC is not a GM specialty.
Originally Posted By: FetchFar
One possible problem could be inadequate flow to the chain. Might explain why the GM High Feature V6 chains have had higher failure rates. .... Does anybody know how these chains are oiled? I think I see a squirt nozzle next to the chain in the picture at this link:
That would be a huge oversight of a most basic and critical design aspect, I would be shocked to think any automaker could develop a new engine series and overlook that!
@OVERKILL: I'm not sure what Chevy's reason for shortening the OCI would be. Is it actually accomplishing something, or does it make it look like they're trying? Timing chain wear notably was near the bottom of the list of worries in the taxi fleet with small block Chevy motors, and those weren't short OCIs. Fuel dilution or tiny little abrasives have been suggested in the thread, and those are as good an explanation as any, aside from manufacturing defect in the first place.
SBC timing chains are a totally different animal, way shorter, way beefier, far fewer links to cumulatively add length from wear, which they were again more resistant to. In an already somewhat challenging aspect of modern engine design (the longest, lightest, lowest friction chain game), it doesn't help that OHC is not a GM specialty.
Originally Posted By: FetchFar
One possible problem could be inadequate flow to the chain. Might explain why the GM High Feature V6 chains have had higher failure rates. .... Does anybody know how these chains are oiled? I think I see a squirt nozzle next to the chain in the picture at this link:
That would be a huge oversight of a most basic and critical design aspect, I would be shocked to think any automaker could develop a new engine series and overlook that!
Shocked yes, yet it could be more oil flow would make the difference. Someone sized those nozzle diameters and passages.
If its nozzle-fed, one hopes all nozzles are pointing consitently at the chain, or some robustness there.
If its nozzle-fed, one hopes all nozzles are pointing consitently at the chain, or some robustness there.
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