jcorenman

Ken,

Let me explain more fully what I tried to say before: You're asking us to accept the tensioner design on faith. We're asked to do that with respect to religion. But this is not religion, it is engineering, and accepting a new design on "faith" is not appropriate. I know little about religion, but I am quite comfortable discussing engineering, having spent my life doing it (I am not a young guy).

Sound engineering designs are based on analysis and testing. And there are some legitimate questions here: the Audi tensioner is well-proven, but it is being used in a different application: A different geometry which may or may not be significant, with a larger belt driving higher loads which may or may not be significant. That makes it a "new design", different from the factory tensioner and different than the original Audi application.

There are generally two ways to prove out a new design: careful analysis, and thorough testing. Generally both are done. I assume the spec's for the Audi tensioner are not available, and we cannot duplicate the original environment (which I believe is an Audi 2.7L 4-cam V6). So the best we can do with a design analysis is to compare loads, resonant frequencies etc with the original application: If those match then we can "inherit" the confidence in the original design.

That is not simple (measuring dynamic tension of a moving belt is not trivial) and I assume you haven't done it. Which is fine, because a design can also be proved out with testing. Which is what we are all doing now.

I have reasonable confidence in the design, and we have your tensioners in both of our cars. But I do consider it experimental, and I keep a careful eye on them. I am happy to do that because we work on our own cars, and if things start to look unhappy then I am out a bit of labor. And if things come apart and wreck the valves, well it was my choice. Personally I think there is very little chance of that, but I am not 100% certain that the Audi tensioner won't suffer premature failure because of the change in its application.

Guys with professional shops have a different basis for their choices. If a part fails, they own that failure and need to make it right. That's quite different than you and I.

So in GB's position I would be asking for exactly what he has asked for: the data to support a design analysis. It's not available, and probably can't be available with the means available to this community. And there are differences: The Audi tensioner was designed for a smaller motor, the belt tension is lower than Porsche intended, and the damping is handled differently (and almost certainly better). Those things may be just fine but the only way that we know for sure is by thorough testing. When hundreds of tensioners have gone six years and 60,000 miles then the confidence level will be very high. But we're not there yet.

My suggestion is that it is not reasonable to expect professional shops to be part of the testing program, and it is not reasonable to criticize them for declining to do so-- or for asking for the data that they need to get comfortable with a design in lieu of extensive testing.

Cheers, Jim

Cosmo Kramer

So did Formula94 ever resolve the cam timing issue, you know, what this thread was originally about?

blown 87

Do you actually think I enjoy pulling the cam covers off to set the cams up Ken? That is friken stupid.

My whole issue is that you just picked a random tensioner and made a bracket for it, the only testing that was done was on your car before you started selling them.

Who do you think is going to pay for bent valves if one of these lets loose in 50,000 miles?

Direct question Ken, are you going to stand behind them if they start to fail and pay for damages or is it going to me left up to the guy that put them in?

All any one has asked for was information and you get all defensive and rude, and yes after being treated the way you have treated some of us we retaliated some what.

Remember when I asked you about that loose fitting set screw to replace the pivot in the water pump, you said just use RTV, it has been working.

I voiced my thoughts on this to you and "it has been working so far"

That scared me if you were not concerned at all about a loose set screw that goes into a water jacket that was there to keep coolant inside the engine and off the belt, what else were you not worried about?
I voiced my concern to you and to Roger about this, and I think there have been some issues with that IIRC.

So here are my concerns, you picked a random tensioner, made a bracket to fit it, did not use the factory tool to set up or find out what tension the belt was being run at and then use us as test subjects.

Did you get lucky and pick the right tensioner out of the thousands of them out there or have all of us early adapters gotten lucky so far?

My biggest issue is that you seem to get upset when asked valid questions and say things like "Works on a Audi" this is not a Audi.
You try to use that over and over again to cover up any lack of real testing that you have done.




I do not even know where to start with that, I am neither Greg Browns partner nor am I willing to fight his battles for him, my guess is he needs no help with you.

What does it make you look like when you refuse to give straight answers to questions?
I asked Ed a a question I had about his water pump and got a straight answer, and that is one thing I have learned I will not get from you, a straight answer.

One more time, who eats the repair bill if I install one of these on a customers engines and it fails before 50,000 miles?
You or me?

I have yet to be condescending to you or rude, you how ever have been both to me and lashed out at me for asking question and voicing my concerns, and because I have a financial stake in this, I think they are valid concerns.

Vilhuer

Probably doesn't make much difference as numbers are estimates anyway but that engine is very early prototype which used carburetor and didn't yet have washer tensioner setup. Notice how there appears to be plate where tensioner roller is mounted and bolts to secure it to block and adjust tension.

soontobered84

Cosmo,
I suppose he finally got it straight.

https://rennlist.com/forums/928-foru...mly-happy.html

Jim,
A great post. Perspective is a key thing here. I currently have standard tensioners on all my cars. If I choose to install other than stock standard tensioners, I understand that it is me to blame if something untoward happens. Anything other than stock is experimental as far as I am concerned.

Greg N.,
Kudos to you for continuing to voice and explain your concerns and perspective in a calm and relatively non-confrontational manner.

Guys,
We all want whats best for our cars. What may be best for my car, may not be best for your car. It would've been nice if Porsche had continued the R & D for these cars and continued to support them. They didn't. It is up to all of us to do the best we can to keep them on the road. I personally like the idea of upgrading the car in all areas whether it be Kevlar reinforced fuel lines, increased HP via stroking/blowing or turbo'ing, or a different idea for tensioning the cam belt. All these things are steps in the evolution of the car.

IMHO

Mrmerlin

and there also appears to be a tensioning bolt thats applied to the plate in a similar position as a tensioner bolt would be

blown 87

Yes, we do want that, or at least I do.

Bill Ball

I don't want to get any more involved in this argument other than to report that I observed the same problem with the threaded plug not sealing. RTV was not an adequate solution. Ended up cutting most of the shaft off the stock part and using it, providing the same seal as stock. I have helped several people install these tensioners on their cars at their discretion, not mine.

SeanR

Same here Bill, I won't use those plugs. I leave the stock part in the pump.

blown 87

That is exactly what I did.

Mrmerlin

so is the pug not deep enough /
Does it have loose threads??
could you not just screw in a short bolt with some pipe sealant on it and be good???

Bill Ball

The plug has no head and seemed a bit loose to me as well. It threaded in with no resistance and nothing to stop it. That bothered me from the get-go. I think a bolt could work, although the stock shaft appears to be machined flat underneath and we know it seals, so we went with that after the first ones leaked.

Rob Edwards

I just left the shaft in there as well. Can't recall whether I used any sealer on it, no leaks to my knowledge.

Bill Ball

Right. There's no reason not to leave the shaft there.

SeanR

That is exactly what I have been doing. I cut a few of them off and then decided that there wasn't a need to.