PorKen

Jim, I appreciate your acceptance of my designs, but disagree that good and gooder can live happily together.

In my opinion, the factory design is not so good, and the PKsn'r is much gooder, also my opinion. Constant control of the belt makes for a smoother running engine. No-one is forcing anyone to buy a PKsn'r. From Roger. Today!


I believe I have metered the appropriate responses to the aforementioned parties. If my sense of humor offended anyone, so much the better.

GregB espoused his opinions. I countered. GregB said things that were false. I corrected him to the best of my knowledge. By his own admission, Greg is a 'heavy hitter' in the 928 world. That doesn't give him immunity from being wrong headed.

danglerb? Seriously.

RKD in OKC

Seems to me the only real complaint about the PKsn'r is no contact switch for the toothed belt service warning. I am personally unfamiliar with how either tensioner actually works but it seems to me that if you could just add a contact on the PKsn'r that will activate the Toothed Belt warning when the belt stretches too far there would be no more comparison. Maybe you could make it an add-on for those that already have a PKsn'r.

I'm sure nobody has ever thought of that before

danglerb

People tend to screw up the timing belt service all the time, so I think in most cases which system they choose doesn't matter enough to argue about it. Billions of miles of experience with the factory system vs zero of Porken's systems being used for even ONE service interval of 50k miles, makes it REAL easy for me to remain a spectator.

I can hardly wait for the open minded and fair discussion of water pumps surely to follow.

JHowell37

I think "billions" of miles of service is a gross exaggeration. The only things that would have racked up billions of miles of service might be the hundreds of thousands of Audi/VW/Seat/Skoda vehicles that use these parts.

GlenL

Do the math.

61000 cars. 100,000 each on average. 6,100,000,000 miles total.

Changed your thinking?

Cosmo Kramer

Here's an answer, put on the PKtensioner and for peace of mind pull your timing cover yearly and check with a kempf tool and inspect the belt/gears. If the belt was loose on Porken's system there would be some definite signs as this would mean the hydraulic tensioner would either be collapsed or at the end of it's stroke Would that not satisfy both sides of the argument?

Landseer

I know how to live with the stock tensioners.
But I want the Porkensioners.

There are alternate ways to engineer things.

SteveG

With the Pkn in place, you cannot use the Kempf tool. Ken has already stated here that the only check is to measure the piston and compare that with the a measurement taken at installation. Rick, I'm sure you are following along ; here is something for you to do while salt is on the streets; has a couple thousand on it, but should be useful as "new" measurement.

syoo8

No. For me, this kind of arithmetic isn't persuasive.

There were 27 fires out of two million subcompacts that Ford built in the 70s-- probably 1-2 hundred billion miles or so logged. Doesn't make this particular model's fuel tank-- the Ford Pinto's-- well-designed.

Is the lack of a "BELT TEN." light really so bad? My old Lexus V8 had no timing belt light in the dash-- you just knew to change the belt every 50-60k miles. Isn't that what the Porkensioner does for the 928?

My common sense tells me-- and I'm a relative newbie on the board: if a "belt tensioner" system requires one to get in and adjust the TB manually a few times after a TB job to account for stretching in the belt-- then is it really isn't doing its job? Shouldn't the system properly tension the belt automatically-- like a PKsn'r?

blown 87

It has offended some, that much is a given fact at this point.

My .02$ is you owe Greg Brown a apology, you questioned his morals and integrity, I think he had every right to be pissed.

SteveG

.02 ---

Re checking the stock tensioner. Porsche recommends re-tensioning a new belt at 1,500 to 2,000 miles. My experience on two belts is that it did need re-tensioning, but only once, however neither of those two belts I installed, has or had over 5,000 on them. For peace of mind I remove the pass cover and inspect the belt and gear once/year.

I don't think people are giving enough mileage credit to the Audi tensioner. Given the engine design is very similar, and the number in service on Audi products, I think it far surpasses the # miles on the stock tensioner.

GlenL

My post was in response to someone who said "billions is a gross exaggeration." Obviously billions is correct.

The Pinto gas tank is an interesting example. 27 is trivial unless it's you. Ford actually did a calculation that the fires were economically acceptable. In practice it's trivial as well. How many people fell asleep in their Pintos and simply drove off the road? Or hit ice on a curve? The tank risk was small in the larger context of all danger faced by the occupants. Knowingly shipping the defect was a mistake.

No one has said the PK tensioner isn't nice. The discussion is over the need to replace the existing tensioner. How many engine failures are due to the stock tensioner and not user error with it? To make a meaningful technical comparison you've got to know the use of each and the failures of each. An emotional decision doesn't need any of that.

dprantl

This is a philosophical debate. If the tensioner was simpler and didn't require so many odd parts to keep working right, would it save more engines from valve death? I do think so. For someone that does not know about online 928 web forums and does not have a workshop manual handy, they may never even know there are plastic bushings in the tensioner arm. And that idler roller on the water pump housing that is not touching anything, why? When you have a bunch of idlers trying to compensate for belt flutter, I'm sorry but that in my opinion is a bad design. When that belt is slapping against that idler while the engine warms up, the belt wears faster.

There are some people that cling to the belief that everything an auto manufacturer engineers into a car is perfect and cannot be better. This is simply not true, mistakes are made all the time and many times there are better ways of doing things. We will see in a couple more years how Ken's tensioner performs with regards to longevity. I'm confident that it will do just fine, and in fact will greatly increase the useful life of the belt.

Dan
'91 928GT S/C 475hp/460lb.ft

blown 87

How long do you plan to run yours?

dprantl

I will stay with a 60k mile interval. With the stock tensioner, I have heard of belt failures in as little as 30k miles. The reasons for the failure almost certainly include user error of course, but I'm willing to bet if Ken's tensioner was fitted to that specific car instead it would have lasted 60k miles and further. Most of the belt catastrophes I have seen are from the shoulder bolt bending and/or the plastic bushings disintegrating allowing the arm to tilt and the belt to shave itself away.

Dan
'91 928GT S/C 475hp/460lb.ft