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Too much "tension." Funny if that was intensional ;)
BTW, I use a stock tensioner, belt too. Does that put me back in your "cool club?" 8400 rpm with the 280's and no instantly broken belt or tensioner. Not sure where anyone was saying stock components are crap.
Hey, before hitting the track or dyno today, maybe you can bounce over to the thread stating you are 800hp uncorrected now and post your chart.
I would take SOHC out of the equation since the tensioner is a basically a solid tensioner which is comprised of a tensioner pulley tensioned once and then secured in place with tensioner pulley bolts with a spring attached to it as safety mechanism.Quote:
Originally Posted by j2k4
The belts do stretch, the fiberglass cords do not stretch. The OEM belts from the dealerships are not the same as any newer Gates belts that are manufactured for the 3/S even in OEM form are far different from OEM belts seen from the factory.
And we should believe this:
After seeing this:Quote:
Originally Posted by Boost4VR4
:rolleyes:Quote:
Originally Posted by aaronatstate
Explain why timing belts break without any outside interference causing the break if they don't stretch?
I have never seen a belt fail that didn't come from one of the pulleys locking up or foreign object damage.
I suppose you're right something always tends to get in the timing area and touch the belt while moving causing it to start to wear faster.Quote:
Originally Posted by Forest Gump
I mean, what about when a belt is subjected to hot/cold spells, does the belt expand/contract at all?
Coefficient of expansion for regular nitrile (not highly saturated as is used in most timing belts) is 235e-6 C.
For 1 meter of regular nitrile with no reinforcement, that's a total of about 2cm to go from 0C to 100C.
Considering HSN is bonded tighter and the belt has fiberglass cords, I would expect it to likely be smaller.
Again, speculation and just basic physics knowledge, but would seem unlikely to be a large change.
HSNs operating range is from -30F to about 300F
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This is why the SOHC tensioners were even brought up. What is it about the DOHC that requires it have the hydraulic system that the SOHC doesn't? Does the DOHC see that much more load on the belt? Does some kind of thermal expansion of the heads push the cams apart and dynamically change the tension or something? Or is it just related to the way that the belt can relax depending on cam position when the motor is shut off? Knowing exactly why the SOHC can get away with a fixed tensioner and the DOHC can't could help provide light into the decision that plays into a new hydraulic or a solid.Quote:
Originally Posted by Boost4VR4
Ok in that respect, if you want to know why, I think it's pretty simple. The load would be greater because the DOHC heads have double the components compared to SOHC. For better flowing heads with more intake and exhaust ports, the sacrifice is additional intake ports and exhaust ports, smaller piston to valve distance and longer belt.
I haven't messed with SOHC much, but I did do a waterpump and timing belt on my dad's old Chrysler New Yorker, sohc 6g72. No need for cam lockers. You put the gears at the marks and they stay, perfectly. I'm sure someone can explain, but I assume it has to do with the intake and exhaust springs acting on the cam in exact opposite forces? No idea if that has anything to do with the lack of hydraulic tensioner, but it was an observation based on my only experience with it.
It's been awhile since I had my timing belt off, but I recall the cam gears on my Stealth not staying exactly put. Then again the SOHC in the Chryslers wasn't exactly the same as the ones in the 3s's.
Double the cams, double (not exactly I'm sure) the length, half the clearance and double the horsepower.
Idk what sohc's rev to but I would think its less than 7k from factory. Even if it isn't, there is significantly less load due to a lot less horsepower (especially compared to tt's). All of these things stack on each other and create a significantly different system
DOHC NA isn't double the HP. It's like, realistically, 30 more HP.
Also the SOHC revs to 6k.
I think, given the SOHC's greater utility/reliability - I mean, ALL those fucking vans and other passenger-hauling sedans - it didn't require fancy valve-train hardware for those uses, beyond it's being overhead/lightweight relative to that little bastard 3.3, the fact the engine made a cameo appearance in the base models of the 3S wasn't reason-enough to warrant a different tensioner for one quasi-'performance' app in a Stealth.
If a hydraulic had ever been developed for it, there's no real reason to expect it to act differently, except to what extent you see belt deflection
I really doubt the belts stretch by any measurable amount... I'm pretty confident any perceived stretch is simply the belt teeth taking a firmer set into pulley teeth. They do wear though, so over time they will appear to get longer. As I posted before, It only takes a thousandth or so of length difference to cause a visible movement of the tensioner.
There is nothing wrong with a solid tensioner provided the belt is properly adjusted. (loose enough to provide proper tension at operating temperature.) The primary advantage to the hydraulic tensioner and it's active operation is extended belt and component life. Many of the motors I've seen do a running change from a solid to a hydraulic have simultaneously increased the service interval by about 50%. (I.E. from 60K to 90K) If you're prepared to check the adjustment periodically, and replace the belt more often, then a solid tensioner would do just fine. In my personal opinion, it's step backwards, and I would only consider it on a motor with big cams and heavy springs, and the primary reason I would do it would be to facilitate getting rid of the eccentric adjuster pulley.
I've ripped my 280 cam, double spring (at the time) up to 8400 on multiple occasions on stock components. Hit 8600 a few;) times in 1st and second but decided to drop down rev limiter since I have zero restraint with the right foot. No ill effects noted on timing components but time spent at those rpms were limited. Actually still running that belt and tensioner after changing up the setup down to stock cams and will be running both again on 280's again:D
Somebody send him a kevlar belt! I want to see if there is a difference.
The belt and tensioner are both already on their way to him. Believe me, I am anxious to see the results.
For me, the solid is peace of mind as the car will be driven very sporadically and I've managed to have quite a few things go wrong with the car, I've gotten less than 3000 miles out of it in 3 years and that includes a round trip up and back to NY (1600 miles.) So I'd rather just trust that the tensioner will hold and then adjust tensioner before taking the car out on a drive or something instead of having something else go wrong.
cool anxious to see. I wonder what the effect of beefed up valve springs would be at certain RPM ranges.
According to the tracking, belt and tensioner should get to Maddog on Monday.
As far as the springs, I've often wondered that myself. I recall that there used to be a lot of speculation that higher strength springs tended to overpower the tensioner when it sat, but I have no idea where that ended up. I'd guess that it would put an increased strain and vibrations into the belt as it goes through the RPM ranges, but I may be wrong. Don't think we can test that unless someone wants to build a rig to test their own motor with upgraded springs. I'd love to build a test stand of some sorts, would be awesome to be able to test out a motor before installing it and know for sure everything is good. But that's a lot of wiring and I'm a lot of lazy.
I thought Jack T. determined the cause of his infamous motors demise was from way to beefy of springs collapsing the tensioner.
First off, awesome vid Dan! Love to see videos of things like this!
In belt design there is always a slack side of the belt, and this is where the tensioner pulley is located. As the slack in the belt changes, the tensioner is there to take up the varying slack. As my earlier quoted post said, timing belts with fiberglass cords do not stretch. The reason the belts appear to get longer as the motor is running at higher rpms is because the force on the belt is higher. As the force goes up, the teeth begin to compress and the belt starts to get more slack, and the tensioner is there to make up for that.
The stock Mitsubishi belt is the basic design as the Gate aftermarket belt, the Gates racing belt, and any other aftermarket belt. Synchronous belts all have three basic elements, a nylon jacket that is on the face of the teeth, tensile cord members, and rubber. It is there to prevent wear, and to reduce noise.
The tensile cords, which can be made of many different materials. We make belts with fiberglass cords, polyester cords, aramid (kevlar) cords, carbon fiber cords, and even belts with steel tensile cords. All cam timing belts have fiberglass cords, because fiberglass does not change in length. Polyester cord shrinks as it sits over time, aramid soaks up water and grows, and steel just wont break first.
The last component is the rubber. There are many different rubbers we use from EPDM to neoprene, to nitrile, and chloroprene rubbers. The HSN rubber used in cam timing belts has a very high temperature range that it works over, and temperature does not effect the length of the belt. Our racing belt uses nitrile rubber that is reinforced with aramid fibers to make the teeth stronger and less prone to sheering off and compressing at high loads.
Now in production when we build the belts, we actually use a large mold that is up to 48 inches wide, and we basically build a belt that is 48" wide and then grind it to the correct thickness, and cut it to the correct width. After the belt is in its finished state, a certain number of belts are taken and measured for the pertinent dimensions. One of those is length. There is a specified length for every belt we make, and we verify that the belt meets this specification before it leave the facility. The calculation to figure out that length (with two equally toothed pulleys) is:
((#teeth of the belt - #teeth of one pulley)/2) * Pitch of the belt
Just to prove that timing belts do not stretch over time, I measured the timing belts out of my dad's 1980 Honda Goldwing at work after he replaced them. The belts on his bike were probably made in 1979. Even after 40,000 miles and 32 years on his bike, they were still within the specifications!
Lastly, I will try to answer why timing belts seem to break unexpectedly. By far the most common reason we see a timing belt break, is due to mis-installation. There is a minimum bend radius for the belt, and if it is bent beyond this, it can crimp the tensile cord and severely weaken it. Fiberglass is great in tension, but not in compression. Believe it or not, but you could lift a stock AWD 3/S off the ground with the timing belt, it takes that much force to break one. When the cord is crimped, it can reduce this force by over 50%! I will look up at work on Monday what the minimum bend radius is for an 8mm pitch timing belt.
I can measure the belts if you want to send them to me Dan.
If anyone else has any other questions feel free to ask, and if I cannot answer them, I will find the answer out from some of the design and application engineers at work.
Oh and PS just a fun fact, the stock Mitsubishi belt from the dealer is a Gates belt, made on the same line as the racing belts (in Japan). There is no difference in the dimensions of the belts between stock and aftermarket whether its a Gates belt or not. The only difference between them is the materials that go into the belts.
Whew long post...
Been waiting for you to show up. :)
Tooth compression, eh?
Given that the kevlar reinforced teeth shouldn't compress (or compress at much) wouldn't that mean that the belt wouldn't get as much (or any) slack and therefore a hydraulic tensioner would be unnecessary (or less necessary)?Quote:
Originally Posted by aaronatstate
I don't see a downside listed for CF, curious what (if any) it may have aside from likely being expensive as hell. Is it actual CF cords in place of fiberglass, or is it similar to the way that the kevlar is used in the kevlar belts? While not related to the topic explicitly at hand since there is no CF belt for our car (and likely no need for one) I am incredibly interested as I can't imagine the kind of environment that you've got where you would even need a CF belt..Or an application off hand come to think of it. Except maybe some kind of massive supercharger belt drive or a timing belt for a 2000+ hp engine of some sorts.Quote:
Originally Posted by aaronatstate
What separates the type of nitrile used in the kevlar with the aramid fibers from highly saturated nitrile? Is it just the aramid fibers and it's still otherwise identical to HSN?Quote:
Originally Posted by aaronatstate
This would then provide something to look out for when ordering a t-belt from a vendor to make sure that it's not super bent when you open the packing I would assume. Is there any kind of visual way to verify before installation? I would be curious what the bend radius is all the same.Quote:
Originally Posted by aaronatstate
If Dan wants to send the Kevlar (and I guess keep it packaged with the tensioner) to you after he's done with it, I'm fine with that. Just so long as it makes its way back here by May.Quote:
Originally Posted by aaronatstate
Yup, take a caliper and measure the thickness of the belt. Then push harder, it gives ;)Quote:
Originally Posted by j2k4
I will always, always recommend a hydraulic tensioner. The drive was designed with a hydraulic tensioner for a reason. Kevlar reinforced belts will still give some, and the engine will expand as it heats up. All these things change the effective length of the belt, and that is why a tensioner is needed.Quote:
Originally Posted by sergechronos
Carbon Fiber's biggest downside in a drive like this is that it is too strong, just like the steel. Look up our Polychain GT2 belts with carbon cord. They are used to drive machinery mostly, where you need something very strong, and efficient. We run all of our machinery with them. There are some of our Polychain Carbon belts that take almost 100,000lbs of force to break! Another interesting fact is that most of the Top Fuel drag racers use Gates Polychain belts (with Kevlar cord) to run their superchargers.Quote:
Originally Posted by sergechronos
They are all HSN rubber. The racing belts just have aramid (Kevlar is Dupont's brand name for aramid) fibers to make the teeth stronger, mostly to resist sheering off in high torque/load situations.Quote:
Originally Posted by sergechronos
It won't be crimped being put into the box. All of our employees are trained to not crimp belts to prevent them from breaking prematurely.Quote:
Originally Posted by sergechronos
OK. I'm good either way!Quote:
Originally Posted by sergechronos
Would you see any reason why the kevlar with hydraulic tensioner would cause failure? After the thorough analysis and information you've provided I doubt it since the overall length of the belts should still not experience drastic change, although I'm unsure if the OEM tensioner would see any premature failure from perhaps not being worked much.Quote:
Originally Posted by aaronatstate
Would the kevlar be a better choice for higher load applications due to upgraded valve springs? Or is it likely still complete overkill? I guess in short for this, why produce a kevlar belt if the OEM should still be satisfactory (and has been proven to be satisfactory) for builds up to and over 1000awhp? I would assume money (or rather, just because there's a market for them), although I'm not sure what kind of difference in profit you guys see for the kevlar belt vs the original.
Well, I can't lie, I wouldn't mind having you (or Gates in general) examine the belt after the demonstration video..Or once I'm done with it at 60k miles, I think it would make for a fascinating video to have belts at 60k (or as close to it as possible) of the "OEM", the Gates sold under their name, the Kevlar with a hydraulic and a Kevlar with a solid just to see if there is any kind of discernible difference amongst them. Although, Gates probably already did such testing before (excluding the solid perhaps) and my intuition says that there would likely be little difference, but I'd be curious if at the 60k mile point the Kevlar with hydraulic or the kevlar with solid showed any different signs of wear a wear pattern to teeth or something. Slightly more random question: Why the blue paint on the belts? Seems like it just always comes off and makes a mess of pulleys and such. Couldn't they sell it without that backing? Does it serve any purpose?
I don't believe they are hydraulic tensioners. They are hydraulically dampened spring tensioners. Like a coil over suspension piece. The spring provides the tension, and the oil dampens the movement.
Well I can give 1 instance where the kevlar belt is superior. A friend had a garage fire, car was a complete loss. He ended up saving the kevlar belt and re-using it for thousands of miles without issue. And the blue paint, that has to be just a marketing gimmick. With that said I always use oem belts and tensioners, I doubt you will see a difference with the kevlar belt as I believe its just the slack being moved around like described and the tooth compression is very interesting concept.Quote:
Originally Posted by sergechronos
With upgraded springs and other valve train components I would recommend the race belt. It can handle more for longer. The racing belt is superior to the OEM belt. I would be willing to bet on a stock motor the racing belt would last well beyond the 60k mark.Quote:
Originally Posted by sergechronos
The blue paint is for marketing. That being said only the race belts made in japan are painted. The racing belts we make here in Arkansas actually use blue rubber! If you look at a DSM race belt, both timing and balance shaft, a Supra race belt, or any other race belt made in the US it will be blue rubber.
Interesting fact we make belts in many colors, black, white, red, blue, gray, yellow, and green are a few! If you ever buy any Jesel timing belts for a pushrod motor, it's a Gates belt too. Most pro stock guys run them!
Yes there is a spring in the tensioner, but the force is held by the hydraulic fluid. Without the fluid the spring can't hold any amount of forceable tension. I did a t-belt job for a guy and his new out of the box (although non OEM) tensioner failed when I turned the engine over by hand to line up the marks. I pulled it back out and the hydraulic fluid had pushed past the seal. I could easily compress the plunger with my thumb. I grabbed the tensioner we took off and with all my might couldn't close the plunger on it by hand.Quote:
Originally Posted by donniekak
The spring provides the static force, the fluid dampens any movement. I have a couple I should cut apart and look at, I've always been curious how the damper is set up. I doubt it's a stack, probably just a pinhole in a piston.
I went solid due to the new oem tensioner collapsed after sitting 2 week. I had to use a screw driver to get it to return to the pin position. Skerd!
If it is just a spring how can they go bad?
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Sounds normal.... Did you turn the motor over before trying to pry it back? Over time the valve springs overcome the tensioner and allow the cams to turn slightly, putting all the slack around the water pump. if you turn the motor over it will recover. Prying the tensioner out just takes up the slack and turns the cams back where they were...Quote:
Originally Posted by CoopKill
It's a hydraulic dampened spring... If you blow a shock, your car still sits level, but the suspension sure doesn't work very well. The viscous fluid in the tensioner keeps it from compressing rapidly. Without it the tensioner will just bounce around, make a bunch of noise, and probably allow the belt to jump.Quote:
Originally Posted by Forest Gump
Not sure if this will link here.Quote:
Originally Posted by RealMcCoy
http://www.stealth316.com/images/stim/tim_09-07.gif
Thanks for the belt Bryan. It showed up today and I should have it on later this week.
Parts of this thread have been a good discussion. I'm interested if there will be a difference.
Aaron I did notice this belt was painted and made in Japan. I was hoping I could blame you for the poor paint job ;)
Nothing says you can't blame Aaron for the poor paint job..This is the internet after all :D
After all this discussion I'm not expecting to see much of a visible difference but never know.
Which belt did you buy, the Gates?
Yeah. Gates kevlar belt, Ninja solid tensioner.
Will have to check mine to see if paint or rubber. :( I got the paint/squeal like a pig one last time.
I would imagine it'll come off unfortunately and eventually start the whine. Pity we can't get Gates to just offer it without that paint.Quote:
Originally Posted by CoopKill
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