changed belt last week ,97 nsx 107000 miles ,13 yrs22k miles , since last changed (5/08 85000). the original belt looked like new this one was even better .After i let it warm i checked the engine vacuum === 21 inches steady gauge , same as is was in 08 . My son is an engineer that has test equipment in his lab to test these belts . just for shits and giggles i will buy a new belt , stress all all three of them to failure , waste of money ,yea , but it will be interesting !
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Timing Belt just changed
- Thread starter ralph cerbone
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I look forward to the results.
I remember my best friend telling me about the lawsuit against Honda for a belt snapping, and Honda’s answer was to establish an interval for replacement.
Will be very interested to see how they go!
Interesting experiment. Is the stress test going to determine the ultimate tensile strength of the belt - just before it fails by snapping? That may or may not provide some useful guidance on how ageing affects the UTS; however, I expect that these belts operate well below their UTS. Harley Davidson's use gilmer belts that are not that much different in size than the NSX timing belt. They operate at much lower RPMs; but, much higher tensions and the more common mode of failure is not tensile failure; but, tooth damage. Gates offers some interesting observations on what they call premature belt failures, most of which are not outright 'snapping' of the belt.
Timing belt failure symptoms, causes and corrective actions | Gates Europe (gatestechzone.com)
On a Harley, loss of a teeth is typically non catastrophic. On an NSX, its catastrophic if the lost teeth result in the belt hopping teeth leading to a valve bending episode. Years ago I had a neighbor who had a Fiat 128 that had a timing belt failure; but, it was caused by the belt slipping / hopping, not outright separation of the belt.
The Gates website does site tension and misalignment as the causes of tooth failure. Perhaps the most important preventative factor in doing the timing belt change is that most people change out the tensioner at the same time. I can see that a tensioner problem or tensioner bearing failure could lead to belt failure pretty quickly. In terms of premature complete breaking failures Gates sites careless handling of the belt during installation and foreign objects getting in between the teeth and the cogs. Along with the oil contamination issue, good cause for keeping those timing belt covers in good condition. I use to have a Volvo with a B230 turbo motor. It was trendy for owners of the B2xx engines to dress them up with an anodized adjustable timing gear and then remove the plastic timing cover to show it off. I figured that was a recipe for failure.
Timing belt failure symptoms, causes and corrective actions | Gates Europe (gatestechzone.com)
On a Harley, loss of a teeth is typically non catastrophic. On an NSX, its catastrophic if the lost teeth result in the belt hopping teeth leading to a valve bending episode. Years ago I had a neighbor who had a Fiat 128 that had a timing belt failure; but, it was caused by the belt slipping / hopping, not outright separation of the belt.
The Gates website does site tension and misalignment as the causes of tooth failure. Perhaps the most important preventative factor in doing the timing belt change is that most people change out the tensioner at the same time. I can see that a tensioner problem or tensioner bearing failure could lead to belt failure pretty quickly. In terms of premature complete breaking failures Gates sites careless handling of the belt during installation and foreign objects getting in between the teeth and the cogs. Along with the oil contamination issue, good cause for keeping those timing belt covers in good condition. I use to have a Volvo with a B230 turbo motor. It was trendy for owners of the B2xx engines to dress them up with an anodized adjustable timing gear and then remove the plastic timing cover to show it off. I figured that was a recipe for failure.
belt test
yes the UTS of the belt , my son looked at the belt and new what is was made of , said "you want me to pull till it snaps and record the data " "yes". i want you to test 2 old belts (one with 85k miles 11 years old ,one with 22k miles 13 years ) and one brand new 0miles on it ." You want me to destroy a brand NEW belt ,whats it cost " ?. 175.00 , "OK ,.. Pops if thats what you want I can do it ,this will be an interesting project .he told me their lab is very busy at this time ,he will get together with their machinist and figured out the tooling that will be needed . stay tuned.
yes the UTS of the belt , my son looked at the belt and new what is was made of , said "you want me to pull till it snaps and record the data " "yes". i want you to test 2 old belts (one with 85k miles 11 years old ,one with 22k miles 13 years ) and one brand new 0miles on it ." You want me to destroy a brand NEW belt ,whats it cost " ?. 175.00 , "OK ,.. Pops if thats what you want I can do it ,this will be an interesting project .he told me their lab is very busy at this time ,he will get together with their machinist and figured out the tooling that will be needed . stay tuned.
The stock TB does indeed stretch over time, the worst one I've seen was visibly longer when laid up against a brand new one.
That would be an interesting thing to check. However, it may be hard to validate. Differences in length could be due to production differences. A data set of three belts has a pretty poor statistical confidence level; but, if the old belts are longer than the new belt that would be consistent with a stretch hypothesis.
couldnt this experiment be done with segments of the belt instead of destroying the whole belt? Ive never seen how long a TB actually is but if say its around 2 - 3 feet of TB material, the test could be done 2-3 times with 1 foot sections.
haven't heard much about the failure of the tensioner. what is the symptoms and if it is mileage related?
my mechanic mentioned that the original water bump was seeping a little when we replaced it long ago. (59k miles/12 years old).
my mechanic mentioned that the original water bump was seeping a little when we replaced it long ago. (59k miles/12 years old).
Possibly a good (and meaningful) test would be to see how the belt would react if one cog is restrained and a second cog attached to a lever, with no slack in the belt and see what happens? Would the belt stretch enough for the cogs to jump a tooth? Or would the teeth fail?
Thats exactly what my son suggested because it would be easier for him to test . Although when we inspected my original belt (85k miles ) i showed him the drive side cog of the belt and how it was worn in comparison to the coast side cog . That's where the slack issue comes into play but you have to have a keen eye to see it . The wear is minimal until you multiply by 241 (number of cogs ) .
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You're right about the tensioner. The WP is more likely to fail.
is there a way to test how much torque in a short period of time it would take to make the worn belt jump a tooth on the cog? Im not sure if the NSX is a interference engine or not but i'd expect one skipped tooth on the TB would not do good things internally.
Definitely an interference engine.
> Im not sure if the NSX is an interference engine
It is, with super long skinny valves.
>i'd expect one skipped tooth on the TB would not do good things internally.
When I got my NSX the previous installer had the belt off by TWO teeth on the rear exhaust cam...drove just fine for 9 years. The same mechanic also installed a new snap ring as a preventative measure for the infamous "Snap Ring Failure".
Based on that...three teeth off would probably be just fine too.
BTW: The car ran much better when *I* installed the timing belt and made the geometry correct. And, later, I had to install a new transmission case housing when the "new snap ring" broke and I went ahead with a full transmission rebuild. Honesty, I find I'm one of the best mechanics I know and I'm not very good at it.
It is, with super long skinny valves.
>i'd expect one skipped tooth on the TB would not do good things internally.
When I got my NSX the previous installer had the belt off by TWO teeth on the rear exhaust cam...drove just fine for 9 years. The same mechanic also installed a new snap ring as a preventative measure for the infamous "Snap Ring Failure".
Based on that...three teeth off would probably be just fine too.
BTW: The car ran much better when *I* installed the timing belt and made the geometry correct. And, later, I had to install a new transmission case housing when the "new snap ring" broke and I went ahead with a full transmission rebuild. Honesty, I find I'm one of the best mechanics I know and I'm not very good at it.
Spoke to my son about progress on belt testing , "Dad we are working 14 hr. days developing new products is this some kind of emergency or are you just having fun" ." Oh no this is total mental masturbation ,you know i love to experiment " ok cool your jets and i will get to it " . This means it will be a while before he can test the belts .
Wow- great concept! Another interesting test would be to cut a very used/old belt and a brand new one, lay them flat and measure any stretch that has occurred. The factory tensioner is designed to take up belt stretch up to the designed replacement interval of the belt- which is why Kaz often mentions to carefully set the belt tensioner during replacement, since you will rely on the takeup throughout the entire service interval of your engine. But, whatever is acceptable stretch is a value Honda determined internally- likely though a lot of severe testing to determine where the danger zone is on the NSX belt. I've seen some old NSX belts (like 20+ year original belts) looking pretty floppy and those cars were still running ok. That said, it would be neat to get some data points on how much the belt is stretching under different conditions. A track rat running hard every weekend in Phoenix or SoCal likely will exhibit different stretch compared to a garage queen that hits the back roads for 3 months a year in Calgary. I wonder what the delta is...
One interesting point is the only Acura timing belt failure I know of personally is on my brother's 94 Integra. It had 200K miles on the original belt and it snapped while cruising on the highway in Phoenix. I have seen a few NSXs skip a tooth (or two) but never fail.
One interesting point is the only Acura timing belt failure I know of personally is on my brother's 94 Integra. It had 200K miles on the original belt and it snapped while cruising on the highway in Phoenix. I have seen a few NSXs skip a tooth (or two) but never fail.
WTH. Inquiring minds are waiting!
IIRC the engine builder for our turbo NSX said the worst case he ever saw of a stretched TB resulted in the rear bank exhaust cam being retarded in the 1-1.5 degree range.
What that means in terms of measured belt length increase, I don't know...
What that means in terms of measured belt length increase, I don't know...
Yea right , whats he doing side jobs take preference , oh i forgot he doesn't work a civil service job . He's a sr. project engineer for a large company with seven people under him in the testing lab . So we have to wait ! stay tuned
It’s all good. I was just funning.
Me too ,I just love breaking his stones ,payback for all my grey hair or what's left of it , lol
Dad i didnt forget , were working on new products ,a lot of stress , I'll play with this when i get time , tell your friends to chill out !
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