M62TU timing chain tensioner - which is best?

[Squiggy]

Hmm. Found this video. I admit I'm a little confused as to whether the spring does any meaningful work after startup. The video says, "as the chain slackens the tensioner is indexed forward by the spring" but I'm not sure what would cause the chain to slacken, other than turning off the motor.

https://www.youtube.com/watch?v=g8ZiLrOibwI

[andrewwynn]

Spring is only for pre-start. Once running oil pressure takes over. Strong logic behind stiffer spring to reduce chain slack at start.

After 165,000 miles, the chain I replaced was about 8mm longer not enough to make the chain slack, but missing shoes on the guides will for sure do it.

If say one of the smaller guides are missing a shoe, might make the chain slack at start but the tensioner can build enough pressure once running to remove it.

[Squiggy]

Originally Posted by andrewwynn

Spring is only for pre-start. Once running oil pressure takes over. Strong logic behind stiffer spring to reduce chain slack at start.

After 165,000 miles, the chain I replaced was about 8mm longer not enough to make the chain slack, but missing shoes on the guides will for sure do it.

If say one of the smaller guides are missing a shoe, might make the chain slack at start but the tensioner can build enough pressure once running to remove it.

Thanks for the clarification. 8mm longer? Wow. I'd wager that is enough to be fairly significant.

[andrewwynn]

Originally Posted by Squiggy

Thanks for the clarification. 8mm longer? Wow. I'd wager that is enough to be fairly significant.

Well within the capability of the tensioner but on the 62 with one chain that should be enough to cause a slight difference in bank one vs. two in valve timing.

Vanos should be able to account for intake variation but exhaust timing is set by the chain length so there might have been a 1-2° difference in the exhaust valves timing after 160,000 miles.

The N62 not only has two chains, and far more robust guides, also four vanos so it can adapt to the requested valve timing and account for some chain stretch.

[CapeX5]

Just for information purposes-if you don't change your tensioner, you get this....

[Squiggy]

Originally Posted by CapeX5

Just for information purposes-if you don't change your tensioner, you get this....

((shudder))

Thanks Kampus! lol

[Squiggy]

While waiting for my new timing chain guide tensioner to come in the mail, I have been thinking about how these tensioners work. As discussed, the spring in the tensioner presses the passenger side guide against the chain, so the chain is properly tensioned at engine start and does not thrash around. Once oil pressure builds, the spring no longer does work because the oil in the tensioner now does the job of putting pressure on the guide to tension the chain. But this begs the question... why would you ever reduce the tension on the chain? Why not simply use a rigid tensioner? Especially if the chain is older and elongated (stretched). I think the purpose of the spring and oil pressure is to increase pressure on the chain over time as the chain falls out of spec over time and becomes elongated. The spring will push the guide in a little farther than when the chain was new. The oil pressure will also push the guide in a little farther than when the chain was new. If I understand this correctly (and I'm not saying I do) the tensioner is essentially designed to elongate as the chain elongates. However, once the chain has elongated beyond the point where the spring or oil pressure can keep proper tension on the chain... you have thrashing even after start up. In this case I wonder if it might be preferable to remove the spring and insert a carefully measured steel pin in the tensioner. If I am wrong about how this works the idea of course is non starter. But if I am correct about how the tensioner works then replacing the spring with steel pin might be an idea worth exploring. You'd have to be really careful not to insert a pin that was too long, but I guess you could start with one that was just a tad longer than the spring and see what happens. If there is still chain rattle while running then replace the steel pin with another pin that is 1-2 millimeters longer than the first pin, and so on until the chain rattle stops. If successful stop there and do not use yet another longer pin, so that you don't use a pin that is too long and puts too much pressure on the chain.

[wpoll]

I think the spring and/or oil pressure allow for the variation in chain length based on temperature. A fix length pin cannot do this...

[Squiggy]

Originally Posted by wpoll

I think the spring and/or oil pressure allow for the variation in chain length based on temperature. A fix length pin cannot do this...

If this is true (or if there are other reasons) I wonder if a compromise, such as placing a steel washer or washers at the base of the spring to make it even longer might help. So the spring is still doing some work even after the oil pressure kicks in. Hmm. Kinda wish I had a beater to experiment on!

[Squiggy]

As promised, photos of the size difference between the M54 tensioner spring (left) and M62 tensioner spring (right). The M54 spring is a beast but it does actually fit inside the M62 tensioner. However, if people are really putting M54 springs in their M62 tensioners they must be cutting the M54 springs down to make them shorter. The M54 spring is very long, but also very strong. By comparison the M62 spring is an extremely weak spring.