im not piling on at all. Been doing this a long time Ken.
You even said it before, referenced me your post that i dont even run oil in the tensioner to make your point, once tensioned, the belt does all the adjusting as it runs over the rollers and pulleyes. so, why is it working on my car?

If all i said is wrong, then:
1. the oil doesnt distribute temp from engine to the discs
2. if you dont have oil the engine temp would take longer to heat transfer to the discs
3. your system can reduce start up, cold temp before warm up, wear
4. you think that the discs really have vibration soaked up by the oil through the little oil port where i say that there is a very low probability of this occurring.

as i have always said, i think the design might work, but im not convinced it works in a racing environment, but certainly it can work for street use. dont think its better, just think its a different way to do a job, and one that will make maintenance a lot easier. (none).

 

Might be better than having someone enlarge the holes, pushing the tensioner to the top of the holes, and then clamping it with 6mm bolts and nuts....thinking it is going to stay there.

I keep thinking/hoping that this is one of your "jokes".

 

I was talking about the seizing/gumming up/dirty roller/rollers. Those who choose to rebuild the original de-tensioner do not want to pay the $250 for the replacement lower rollers but buy the $10 bearing instead. I assume they put back the lower rollers after they replace the bearing/bearings.

Personally I have removed the lower rollers on all my cars fitted with the PKT's. If the consensus is to leave them in place so be it - apart from saving weight it makes no difference.

 

I'm pretty sure it does make a difference....that's what I'm trying to tell you.

Porsche didn't put the rollers there because they needed to spend more money or make the engine more complex.

They put them there to keep the belt from skipping teeth.....on the smallest pulley.

On the very early engines, with the plastic guide, Porsche clearly warned about not turning the engine over backwards, by hand.

Why did they do that?

.....And, if turning the engine over by hand is bad....wouldn't the engine "kicking" back and turning backwards be a problem, also?

The first change Porsche made, in the tensioner area, was to install a metal roller....sittting so close to the crank drive gear that it was virtually impossible for the belt to skip teeth when the engine turned backwards.

Don't believe me?

Try it yourself. Go over to Sean's and try to get a belt tooth to pass between that roller and the drive gear. Oil it up. Give that belt a big *** tug. Get everyone that's removed that lower roller together and have everyone pull on that belt at the same time.

There's an "ah ha" moment there.....

You people that have drank the Koolaid are really tough to logic with.

 

I guess I must learn to speak American English as you misunderstood what I said.
I removed them to save weight - no other reason - so leaving them in place makes no difference to me. Not sure I am going to dig back in and replace them as they have already been trashed. I guess as always I will live on the edge.

I agree and in the future I will leave them in place.

 

Now take that to the next step.

Nearly everyone agrees (I have zero personal experience with the following) that the Porkensioner system doesn't keep the cam belt as tight.

And according to Jim Corenman's data, the Audi tensioner looses a fairly large percentage of its tensioning force, as it gets past "the sweet spot" of 5-6mm.

And the cam belt isn't nearly as soft and compliant as the stock belt.

And the engine rotates slightly backwards, with no lower roller.

.....ba boom.....



To me, the only question left to answer in this thread is why the tensioner extended to 9mm (initially) on this particular engine.....there has to be something wrong, dimensionally, with some part:

Those custom cam gears slightly smaller in OD? Heads got shaved? Audi tensioner boxed incorrectly or defective? Pivot piece forged incorrectly? Dowel in roller incorrectly positioned? Crank gear wear way more critical than anybody guessed? Water pump casting incorrect? Oil pump gear smaller than standard? Ken's bracket slipped in the jig and has some of the holes incorrectly located?

Until all that stuff is checked over and the reason for the 9mm initial dimension is known, this thread is done.

 

I one hundred percent agree. Why was the tensioner out of range on initial install? Why did it get worse? Then obviously, how can the final failure be avoided in a similar situation in the future.
Let's not pretend that no stock tensioner SYSTEM has ever had a catastrophic failure. Let's also remember that Ken's product is also a SYSTEM, ie. a collection of parts working together.
Anyway,
Dave

 

How much do they weigh?!

 

I'm pretty sure that was British humor.
Dave

 

As I run all my engines hard and at higher rpm , I have everything that was stock on the engine , the roller as these are s4s that they came with , are the single roller units , they are shiny from occassionally touching the belt (both gates) .
So the comment on them not doing anything is completely wrong I wonder how many here who are arguing the point have any worthwhile experience on these things or are just internet followers ?
With what I do I believe that if the stock system had a weakness, then I would have found it , and I dont believe that I will, other then regular maintenance .

t am staggered from an engineering viewpoint is most alarming one of the solutions to the PKT adjustment is elongating Holes !!!

With the critical nature of these components and the catastrophic expense of a failure why anyone would consider this.

Looking at the leverage arrangement of the PKT arm the difference if I understand correctly between correct adjustment and wrong (bad) is 2mm ?This is unbelievably miniature I would then encourage all have inatalled one to check asap .
I believe the absence of a tension warning alarm is most bad practise .

Someone also mentioned here that the alarm is a waste of time , what an ignorant statement !

Again I wonder how much real time experience other than internet .
The alarm system setup if maintained works every time low tension occurs faultlessly . Try it and test it I have !!

In my business I receive calls by owners, to turn off Diagnostic trouble lights , of course I refuse , trying to be polite I respond by telling them to FIX THE BLOODY PROBLEM IT IS THERE FOR A REASON (Not only Porsche by the way) the average persons stupidiy is overwhelming , I must be getting to old for this .

Everything wears out over time if you choose not to perform maintenance than you of course assume the risk and cannot complain if something fails expensively.

 

Thanks John. I don't think anyone here doubts your experience or Greg's experience with stock systems. You are both legends, and my respect is unbounded! However, for whatever reason, Ken has tried to improve on the stock system, with various trade-offs chosen by him. Nobody should imagine that components such as lower rollers that were needed with one system, would be needed with the other.
Sorry,
Dave

 

7.41 ounces, for the single roller.
A whopping 10.22 ounces for the double roller.

With dirt.

I'm hoping it was British humor....

 

The weaknesses in the stock system are what require a tension light and guide pulleys by your own admission. This is not a knock. Please continue to use it if you are comfortable with it.

With a tensioner/damper based system the belt does not look like a rubber band. Which I why I believe it is superior. Besides normally requiring no maintenance.

In testing my S3 and S4 chips, I have done many years and thousands and thousands (and thousands...) of WOT runs to redline and many hundreds of dyno runs with a PKT on different 928s in every weather condition without ever a worry, or having to do anything to it.


Note the Audi A8 has a longer belt.

And yet it works. Simplicity. The clamping force of each of three flange head bolts is quite large.

This is not the range.

 

Greg may be using it as thread fodder, but it still has not been shown that the PKT was the cause of this mishap. Or that vestigal crank rollers would have stopped it.

It is also odd that it occurred with such low mileage on the belt. Myself and literally thousands of others now have had not problems with a PKT with many tens of thousands of miles driven each with different types of belts, from Racing to Continental. Many with no crank rollers.

 

You need to go down and be with Roger when he tries to pull a timing belt between the crank drive gear and the lower roller.

Just because you decided it was "vestigal", with zero knowledge of why it was designed to be there, doesn't make it so....