Anyone installed the new Centerline Staybelt tensioner? - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 30 (permalink) Old 03-19-2019, 07:47 PM
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Originally Posted by MALDI View Post
Isn't it true that the fixed mechanical tensioner is either too loose at low temperatures or too tight at high temperatures?

Most people set it tight a low temps and, therefore, it is too tight at high temps.

The lore was that if you go to a fixed tensioner you need to change the timing belt more frequently because you are putting it under more stress than it was designed for.

Variable tension was the logic of the original design. https://www.alfabb.com/bb/forums/alf...tml#post237620
Good point, Maldi, but let's remember that all technology advances, and this certainly includes power transmission systems like toothed synchronous drive belts. Drive belts today are far better and more forgiving than they were in the 1970's and 1980's, for sure. We also have to remember that Ing. Busso did not have a lot of timing belt drive history or collective experience (on automotive applications) to draw upon when he designed that beautiful V6 engine. I seem to recall that Pontiac introduced a SOHC inline six in the mid 1960's, with a belt driven camshaft. But prior to that, how many other manufacturers tried this technology? Not many, if any. Busso was plowing new ground, and he might tell us today, that he had concerns over maintaining the ideal tension. Indeed, he makes this very point in his patent description of operation, if you read it through.

I don't believe that timing belts today require such critical tension parameters.. they are more durable and more forgiving. Whether you buy a Pirelli, Dayco, or Continental belt for Alfa's V6, you're getting a modern improved product. And let's take some credit as Alfa owners, also-- I feel that those who do belt changes are doing a better job on tensioner setup and rebuild, either hydraulic or thermo-mechanical. Thank this forum for that.

I hear your logic about over tensioning with a fixed tensioner, but how can we doubt the success of this product when everyone here who has used a fixed tensioner, reports that they never have any belt failures? It's hard to argue with success. For this reason, I feel like the belts are more forgiving than we think.

Great discussion! I really appreciate everyone's feedback.

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post #17 of 30 (permalink) Old 03-20-2019, 03:18 AM
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I agree. Good quality modern belts should be less prone to breaking or streching.
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post #18 of 30 (permalink) Old 03-20-2019, 10:51 AM
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Originally Posted by cda951 View Post
I might be missing something, but I am not sure how this would be an issue. The Busso de-tensioner design keeps the belt fully tensioned for the first few seconds while cranking a cold engine, which is good because that is when most timing belt failures happen. If the ambient temperature is below freezing and it takes a bit longer for sufficient oil pressure to build for de-tensioning, how would that be a problem?

As a Porsche mechanic with a lot of experience with 944 and 928 timing belt systems, I must say the early 944 with mechanical timing belt tensioner works quite well as long as the factory instructions and replacement intervals are followed. At my shop we re-tension any new 944 timing belt (mechanical or later spring-loaded style) after 1,000 miles to account for belt stretch. This would be a wise idea with any mechanical belt tensioner.

Anyway, thanks to Centerline for continuing to support these cars!
I will take a stab at this, just from a theory standpoint, I wonder if the change from no oil pressure to sudden high oil pressure in very cold temps is the cause of the issue, I believe the oil pressure detensions the belt, so you would go from max tension to max detension very quickly, and this could cause a belt skip.

I also have 944 t-belt experience, not as much as you, but I do have one of the little belt tension measuring tools at home, plus while I was recovering from a motorcycle wreck last year, my GF (soon to be wife) asked my buddy to drag drag in a bunch of spare V6 parts into the house so I could build a spare engine inside the house while I was recovering. It has a new T-belt and an old mechanical tensioner I had, so when my order comes in for the new Centerline tensioner, I will measure the current tension then swap in the fixed tension tensioner and set it to the same tension. I think that would be a good reference for anyone who wants a little more precision than belt deflection. Although when I was home last, the 75-90 degrees was pretty accurate.
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post #19 of 30 (permalink) Old 03-21-2019, 09:27 PM
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Assuming all new mechanical spring tensioner are now aftermarket reproductions, this tensioner is likely a safer bet.
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post #20 of 30 (permalink) Old 03-31-2019, 05:38 PM
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I was home over the weekend and I had a chance to play with the new tensioner, first off it is heavy as in lots of metal and good quality. I started off with the old tensioner which was not quite lined up right, but pretty close.

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The tool I used is one I bought for the GF's 944 when we got it back on the road, below is the tool name and the tensin setting for the 944.

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The best place to take the measurement is on the long end of the driver's side, but the tool does not fit well here, so I had to flex the belt a little and it changes the measurement some, but I could also measure at the top between the cam gears and the tool fit well here, and the measurement was not far off. Sorry the pictures are not the best quality.

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post #21 of 30 (permalink) Old 03-31-2019, 05:51 PM
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There are two issues I ran into. One, the top of the tensioner gets hung up on the bottom of the water pump when installing, and the only way to get it to clear the water pump is to put in the 3/8" extension and put some pressure on the belt and then to turns enough to clear the water pump and it fits flush against the block. The second issue is that you have to have the adjuster bolt at least half way backed out to be able to get the 3/8" extension in the square hole, the adjuster arm is so long that if pushed down to much it will partially cover the hole. But the adjuster bolt is well worth it if you plan on using the tension measuring tool, I was able to go from about .95 on the tool to about .90 with three turns of the bolt. When you loosen it, you need to pull the arm up to get it against the bolt.

I did not get this measured quite right at the time, I was running out of time to play with it, but here is what I ended up with.

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Over all I really like it and will be using it on my engines going forward. I think both issues would be easy to fix with a dremel tool if you did not mind cutting through the coating on the steel.
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post #22 of 30 (permalink) Old 04-02-2019, 06:46 AM
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Originally Posted by SamW View Post
I was home over the weekend and I had a chance to play with the new tensioner, first off it is heavy as in lots of metal and good quality. I started off with the old tensioner which was not quite lined up right, but pretty close.

Attachment 1558938

The tool I used is one I bought for the GF's 944 when we got it back on the road, below is the tool name and the tensin setting for the 944.

Attachment 1558940
Attachment 1558942

The best place to take the measurement is on the long end of the driver's side, but the tool does not fit well here, so I had to flex the belt a little and it changes the measurement some, but I could also measure at the top between the cam gears and the tool fit well here, and the measurement was not far off. Sorry the pictures are not the best quality.

Attachment 1558944
Attachment 1558946
Cool, I had been toying with the idea of buying that tool, though I have the uber-expensive factory 944 belt tension tool at my shop----I have no less than three cars with fiddly timing belt setups (see signature below), but the ArnWorx tool seemed specialized to the 944 so I held off . . . also both tools use some arbitrary unit of tension measurement instead of something universal like lbs per inch.

But kudos for getting it to work with the GTV6; I have this tensioner on the shelf and will be installing it during the next major service/valve adjustment.
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post #23 of 30 (permalink) Old 04-02-2019, 10:05 AM
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Thanks, I was new to the 944 world and after a lot of research went with it, Stephanie paid for it, I just had to use it.

Before you do that, you should contact the company and see if they could modify one for the Alfa. I feel that the best place to measure is is between the driver's (US) side cam pulley and the crank shaft, this is the longest stretch and if the wood (I think the new ones are metal) tab(s) were fitted to the center arm, and the outer arms were just round parts, you could use it on that section of the timing belt without having to twist the belt outward which I am sure changes the measure, at least a little. The one thing that would need to be tested (I guess I could look at it next time I am home) is if the spacing on the outer arms is correct since both arms would have to fit into the cogs of the timing belt.

I am heading down to a friend's house in Ga for the Walter Mitty at Road Atlanta at the end of April, I am going to bring this tool and another Centerline/Zat tensioner to install on his Milano engine while it is out of the car, so I will play with looking at the difference between the tension on the long stretch and between the cams and report back.

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post #24 of 30 (permalink) Old 04-16-2019, 06:26 AM
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I have played with this a little more and was able to remove the temp sensor and fit the tension tool on the long side of the timing belt and the measures there are very close to between the cams, between the cams is slightly looser, but not by much. I also rotated the engine every 180 degrees of the crank on both compression and exhaust stroke and found only 180 before TDC Compression stroke the valve spring tension on the cams gives the measure between the cams a bad reading, it measures loose. So I had the side measure per the tool at .95, between the cams is .96, but at that particular crank/cam position between the cams measured at 1.0 while the side still measured at .95. According to the tool maker, .90-.97 is proper tension for a new belt, so I think I am safe to measure between the cams as long as the crank is on P.
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post #25 of 30 (permalink) Old 04-17-2019, 04:25 PM
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I have played with this a little more and was able to remove the temp sensor and fit the tension tool on the long side of the timing belt and the measures there are very close to between the cams, between the cams is slightly looser, but not by much. I also rotated the engine every 180 degrees of the crank on both compression and exhaust stroke and found only 180 before TDC Compression stroke the valve spring tension on the cams gives the measure between the cams a bad reading, it measures loose. So I had the side measure per the tool at .95, between the cams is .96, but at that particular crank/cam position between the cams measured at 1.0 while the side still measured at .95. According to the tool maker, .90-.97 is proper tension for a new belt, so I think I am safe to measure between the cams as long as the crank is on P.
Cool, thanks for sharing. I think you are OK measuring in either place as both are "downstream" of the tensioner in the direction of engine rotation. Remember the factory Porsche 944 manual's instruction to turn the engine backward from TDC by 1.5 cam gear teeth? This is to relax the tension on the accessible span of the belt used for tension measurement (this span is just "upstream" of the tensioner pulley and is quite tight after the engine is turned in the normal direction of rotation).

And yes, timing belt tension on the same span may vary in different engine positions depending on the load from the valve springs/cam lobes. So it is wise to always measure the belt tension in the TDC #1/"P" position. It would also be interesting to compare the values when stone cold and at full operating temperature, new belt vs worn-in belt, etc.

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post #26 of 30 (permalink) Old 04-18-2019, 03:40 AM
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And yes, timing belt tension on the same span may vary in different engine positions depending on the load from the valve springs/cam lobes. So it is wise to always measure the belt tension in the TDC #1/"P" position. It would also be interesting to compare the values when stone cold and at full operating temperature, new belt vs worn-in belt, etc.
That is why I wanted to check with engine rotation and the different location, and you are correct, "P" is the correct engine position to check. And I am curious about hot engine and used belt also, I am in the process of replacing the belt and water pump on my GTV6 and will install this style tensioner, but I use the can covers on mine and trying to get the passenger's side cover off and not draining the cooling system is not practical. But my buddy with the Milano runs his without covers, so we should be able to check his hot and used. I will help him install it, record the tension, then check it again after some time.

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post #27 of 30 (permalink) Old 04-25-2019, 05:15 AM
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I put this on my GTV6 last night, I am still in the process of putting everything back together. Before i took the belt off I gave it a measure, .97 between the cams, which is the loose end of a new belt and this belt had about 5k miles on it and several years, so I think that is a pretty good reading. Putting the tensioner on the engine in the car is a little more tricky. I backed the adjusting bolt about 2/3 or 3/4 of the way out and I was just able to get it in without too much effort. Centerline supplies a little sleeve that goes over the stud and inside the tensioner hole to remove any slack between the stud and tensioner. I put the sleeve in the hole first and then slide it onto the top stud, I tried putting it on the stud, then put the tensioner on, just could not get it to work. Having it loose on the engine, I could not get the heavy washer on the lower stud, I had to use the 3/8 wrench with an extension to put tension on the tensioner before I could get the washer and nut on, but after that it was fine. I put a fair amount on tension on the tensioner with the 3/8 wrench with extension and that gave me a tension reading of about 0./1.0, so I used the adjuster bolt to get that up to .97/.96 between the cams, turned the engine a complete 360 (cams) and measured again and it was about the same. I am going to try and get the reading to .95 between the cams this evening before I button everything up. I plan to spin the engine over several more times and measure a few more times before calling it complete.

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post #28 of 30 (permalink) Old 04-25-2019, 07:37 AM
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SamW, once you get everything back together, would you be able to make this measurement on the engine when it is hot?
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post #29 of 30 (permalink) Old 04-25-2019, 08:42 AM
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SamW, once you get everything back together, would you be able to make this measurement on the engine when it is hot?
Not on my GTV6, I like to keep the t-belt covers on it, but I am heading down to a buddy's house this weekend to put this style tensioner on his Milano and he runs his without the t-belt covers, so we can measure on his car. Of course his engine is out right now, so I am not sure when we will get the measurements.

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post #30 of 30 (permalink) Old 04-26-2019, 11:37 AM
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Thanks! I am curious to see how great the thermal expansion effect actually is.
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