Imo000

The cause of the problem is pretty simple. The tensioner let the belt stay loose, that's what happened.
What happened to Greg's engine is irrelevant becasue that was with the OE tensioner. Ken stated many times over the years that the Audi tensioner rod takes a long time to retract when pressure is applied. So the ONLY logical conclusion is that the belt was loose when the engine kicked back. So again, the cause of the failure was the tensioner therefore, it would be Ken's job to compile all the info stated by the owner and come up with a recommendation on how to fix this problem.

GregBBRD

Clarifications, above.





There's a far better question to ask....which should end this entire "debate" very quickly.....

Has anyone ever seen a Factory cam belt with a Factory tensioner skip cam timing without the teeth being ripped off?

(Not from a faliure of some other part....but in a situation where all the other parts are still present and not broken off.)

I'll even allow crazy wear on the cam gears....anyone????

The answer is no.

It's impossible and never has happened.

That is what this entire thread boils down to.

OP buys "premium" pieces that he thinks are going to prevent a disaster....and gets 10K worth of engine damage. (Minimum this would cost to fix in any qualified shop.)

NEVER WOULD HAVE HAPPENED WITH A STOCK BELT AND A STOCK TENSIONER!

And that's the real end of this story.

ptuomov

The problem is that the factory tensioner with its (almost perfectly) static geometry when hot will require a very high pre-tension, such that the slack side tension in the worst-case scenario will not turn out to be too low. This causes the tension to be very high in the other end of the scenario spectrum and wearing out all the components that the belt touches faster than they would wear out with a hydraulic tensioner. It's in my opinion not a correct inference to say that the factory tensioner works if the belt only fails when some other component it touches fails, when that other component failure may be caused by the belt tension which in turn is driven by the stock tensioner.

[Add to that the human tendency to believe a frequently malfunctioning warning light and to (incorrectly, like idiots that we are us humans) overtighten the belt. But if we're talking about people who _never_ make errors like that then it's irrelevant here.]

That all said, I think that with stock valve springs the stock system works as the factory intended it. I see no reason to believe otherwise. I am certainly not critical of anyone using factory components and following factory maintenance procedures.

One of the reasons why I ended up with the PKT system was that my valve springs were not stock and I have no idea what the correct pre-tension with the factory style tensioner is with stiffer valve springs. I think that since the springs got a custom load set on them and were installed with as low load as I think they could possibly function with, with hindsight even my engine would probably have been fine with factory stock tensioner and factory stock slack-side pre-tension setting. But as the cams get more aggressive and valve springs stiffer, I think someone using a stock tensioner with those non-stock components should probably make an engineering computation or two to figure out what the new pre-tension setting should be if using the factory tensioner system.

Imo000

Did you buy the cams and springs from a single supplier? If yes, they should give you and answer to your question.

ptuomov

Jim -- I for one appreciate the probing questions you're asking about this system. As long as we're all honestly trying to work out what happens with true facts and no intent to mislead, constructive criticism and probing questions will lead to better solutions. I just wanted to write that out first just to make sure that even if I sometimes end up disagreeing with you on an issue, I think that even in those cases everyone is better off having tried to work out the problem logically.

In terms of fasteners, it's my understanding that the it's the friction between the two bolted-together surfaces and not the bolt itself that is supposed to keep the parts from sliding. Quoting a (fairly practical) book that I use when trying to understand what kinds of fasteners to use where and to understand why the factory used the fasteners they used for different purposes:

"Carroll Smith's Nuts, Bolts, Fasteners and Plumbing Handbook" by Carroll Smith, page 71.

By my understanding, then, these particular joints between the block and the bracket and the bracket and the tensioner should not move. If they are intended to be rigid joints, as I believe they are, there should in my opinion be no gasket in between either joint. It should be metal to metal and not moving. Ken will surely correct me if my understanding of the intended design is wrong.

ptuomov

The valve spring specifications were as requested by me and therefore if they fail the person at fault is staring me at the mirror.

MFranke

Hai asked a good question. If Hai continues tear down we may lose important as-found information. Maybe some of the more knowledgeable folks here on the belt system could help put together a fault tree so Hai knows what to look for, or measure, when disassembling. I heard various ideas about the components like bad water pump, gear sizes, PKT mounting, cam gears, etc. What specifically about these does he need to measure? What info is needed from these so that a root cause or support -refute analyses can be done?

WallyP

I think that it would be interesting to see two sets of tests made:

Stock Tensioner - Check belt tension correctly with engine cold. Run the engine long enough for it to be at full operating temperature. Repeat the belt tension check. Report what happens.

PKT - Check rod extension as found (engine where it stopped) after extended period. Rotate engine to TDC #1, immediately check rod extension. Recheck after a reasonable delay, perhaps an hour. Report what happens.

GregBBRD

Standby....

Like I said, putting together a GT engine that I will run on my test stand and will take every measurement possible. I'll install my upper distributor cap covers with "windows" and actively monitor cam timing, with the engine running. I'll run the engine without the plastic cover and see what the belt is doing.

I WILL NOT run the engine without the lower roller....but I'll remove it and show what happens when the engine is turned backwards, with the Portensioner.

I'll check it with new Factory belt, slightly used Factory belt, aftermarket belt, and even a Racing Belt (if Roger wants to send me one.)

In short, I'll do all the research that the inventor and promoter have failed to do...I'll come up with all the 'hard data" I've been bitching (for the last ten years) that Ken doesn't have.

While it pisses me off that I am the one that has to spend my valuable time and money doing this.....someone certainly needs to!

And you never know, while i'm pretty dubious, maybe I'll become a giddy Fanboi, too!

ROG100

Hi Greg,
As you have done everything in your power to trash the PKT can I very tactfully suggest you recruit a "third party" unbiased observer to record the results - I know you are going to get upset with me for making this suggestion but I think it is important for universal credibility.

If I had a RTB I would gladly send it along but none have been made for a few years now. They became too expensive at over $200 each. I doubt anymore will be made - not ordered by me anyway.
Good luck with your tests.
Roger

GlenL

As an engineer in new product development, I know that creating a new, reliable product is about working the details. Truly, it's "1% inspiration." Testing at the extremes of conditions, and combinations of conditions, is hard and costly work.

I see in the thread that water pumps may be different, block and heads may have been machined and there are multiple belts made. And then there's aging of the belts and the tensioner. And engine temperature ranges. And ambient condition changes. And engine variants.

Sound expensive and time-consuming? Yes, it would be. Done well the testing would be prohibitively expensive to creating this product.

The part that bothers me is that the new tensioner was really a solution to something that's not a problem. Belt failures are not tensioner failures but are human errors. With billions (yes, billions) of miles on the cars there'll be failures and we can identify the faults. The tensioner design isn't one.

ptuomov

Now, since you brought it up, aren't you selling modified early Laso water pumps that will fit the newer cars with the stock tensioner? The alternatives for someone who owns a later model car and wants to use Laso pump are either to (1) buy the more expensive pump modified by you and use the stock tensioner or (2) buy the less expensive unmodified pump and use Porken's tensioner. It seems to me that whether the PKT product works or not _does_ have something to do with you. It seems to me that you _do_ have a non-zero financial stake in this subject. You obviously have something personally at risk with your pump modification venture, if nothing else then the working capital. Right?

Note that there's no criticism here of your water pump product. In fact, I think it's a good product to offer and it's priced reasonably.

GregBBRD

Seriously...you are a work.

I don't begin to make my normal shop rate modifing water pumps....I started doing them to help out my own customers.

I offered a very short run of modified Laso pumps as a service for people who didn't want to spend the money to buy a factory late model pump....or be stuck using a Poortensioner.....not as a huge profit making thing.

"It's not a product"...it's a modification.

ptuomov

You running a charity would be more credible if you wouldn't attack every even remotely competing vendor with logically and factually suspect arguments.

928 at last

I may have missed something along the way here (and it's quite possible), however, has anyone suggested, or has the OP tested the Audi tensioner itself? These things do fail, and at widely (wildly too) different mileages.......(I was talking about this thread with a very knowledgeable source on Saturday....). I've had essentially new Bosch fuel pumps quit for no apparently good reason, and yes they were the real Bosch units.
Just might be something to seriously look into.
"Just 'cause it's new doesn't mean it's right".