This is news to me, Sterling hasn't said anything to me about his concerns on it being the PK tensioner. Do you have some information we don't?

 

I'm not sure my situation is relevant.... I don't even have it apart yet, much less have a cause figured out yet. There are people that have many miles more than I do on these without problems.

 

I do not have the Porken tensioner on either my '89 manual or '94 auto, but am seriously considering it for the '94.

I can speak with a bit of experience regarding a 32 valve Audi V8 engine - their 4.2 liter that is in the A8, and an option on A6's. The engine, much smaller at 4.2 liters than our Porsche engines still produced ~295 hp and 295 ft lbs of torque in my car.

I'm not familiar with the exact tensioner in the engine of the car I had (a '91 V8 Quattro manual), as I never replaced the belt myself. Audi's maintenance program for that car was to replace the belt at 90K miles. I drove the car for 135K miles before trading it, and had the belt replaced on schedule. No problemos - a great car.

Gary Knox

 

Lucky is, as lucky does. I am nothing, if not lucky, that's for sure.

Not sure why you reflexively ask for a statement like this every time there is a mention of the PorKensioner? Most, if not all of the development work was posted on Rennlist from the beginning. It's no secret that I found a tensioner which fit well, then did on car testing on 16V then 32V engines to find that it worked well.

Remove the center cover and watch an engine with the stock tensioner at 5000+ rpm, then do the same with a PKT. There is literally no belt control with the stock tensioner, it flaps! With a PKT, the belt is always dead flat. I doubt anyone, (especially anyone named Greg), would dare take an engine with a stock tensioner and rev it up over 5000 when dead cold - I wouldn't - but I've done this many times with a PKT - with no 'guide' pulleys - not to mention literally thousands of WOT and dyno runs from 2000 to 6700 RPM with my 32V engines (auto and manual) testing my S3 chipsets.

The AUDI 30V tensioner system works great. As shown above, the belt layout is very similar to the 928. It's seriously overbuilt compared to the 928 system. It fits w/o modification. It doesn't require high static tension to keep the belt on the gears - cold/hot/at high rpm. Yada, yada, yada.

There have already been belt replacements at 45K+ miles with a PKT. Now the interval has to be in the millions to be worthy? Laughable.

 

This is really all I need to hear. I followed along with the development, and this is what I expected from the beginning. This type of tensioner OUGHT to be superior. It is a better design.

So I am getting that to be on the safe side, one would follow standard TB inspection and replacement intervals.

 

You are right about one thing, this Greg is not going to run a cold engine up to five grand.

 

I dont have it in front of me (the Porkentensioner install booklet) however I remember there was a measurement of the piston travel that you could take. If the piston travel was more than >9 you were supposed to replace the tensioner dampner. .. This seems reasonable as you should be inspecting that area once a year or every 30 k miles (IMHO).

From the install PDF -

Using a caliper, measure the extension of the tensioner piston at the middle of the piston from the
tensioner body to the lever. Piston extension must be >2mm and <9mm! Max extension available is 11mm.

 

Feel lucky to have aftermarket parts.

30 year old mechanical engineering vs modern.

Hmmmm.

A no brainer to me, regardless of the maintenance interval.

Then again, most people think I'm a bit off the wall, for pushing the envelope to begin with.

 

Add up all the miles put on the TB system with the Ptensioner.....it may not be millions but it will be quite a representative sample.

I have 2 stock tensioners in my spares bin and no intention of doing anything with them.

I've +20k on my Pkensioer and belt with zero worries and I have one of the 1st systems that Ken sold direct

 

+1 for Ptensioner. Very happy!

 

I dont think its fair to say that Ken " made a bracket for a random tensioner".

Looks like he carefully selected a tensioner from a motor of similar design. Good Job Ken!

Don't stop innovating.

 

I have no opinion relative to the quality or function of the Porkensioner.

I have tried a couple of other "enthusiast designed" products to near disastrous results.

Does the Porkensioner solve a problem that does not exist? Though relatively a noob in my tenure here, I have read many many thousands of threads and not once have read about a failed stock tensioner causing a major malfunction. I repeat, does the Porkensioner a fix for a non-existent problem? How many people can point to the stock tensioner as the cause for their TB failure? Most of the ones I have read about are water pump related.

I am not positive but it seems like most of the racers are running the stock tensioner. As they represent the best present day stress testing of components, their opinions carry a lot of influence with me.

Ken, I am not deriding your product and the simplicity of its design and apparent good operation, but there needs to be a few more miles/years of service examples before I can with confidence install yours. Even then, there needs to be some operational benefit demonstrated. As some have referred to possible reduced cam gear wear, then that would be a big plus. Long term evidence of just that would justify use to me as long as the Porkensioner itself was benign at a minimum.

One last thing, do you believe the Porkensioner improves engine performance because it keeps the belt more evenly tensioned and reduces, near eliminates, the high rpm flap of the timing belt?

 

When belts are flapping it becomes the cause for shaving and they wear much faster this is the case with any belt whether they drive pulley's or gears.

Belt wear Fatigue, more so than abrasion, is the culprit for most belt problems. This wear is caused by stress from rolling around the pulleys. High belt tension; excessive slippage; adverse environmental conditions; and belt overloads caused by shock, vibration, or belt slapping all contribute to belt fatigue.

 

Hard to fault the stock tensioner unit itself for TB failures. It's essentially a bolt. Consider the entire tensioner system, however, and you'll collect a lot more data.


Would you rather have:

A system with plastic bushes supporting a long arm, secured by a shoulder bolt (<S4), a stamped steel/round edge pulley with a meager bearing, operated by a 'tensioner' with a subjective, temperature related, de-tensioning ability only. 'Guide' pulleys are required to keep the belt on the crank gear when started cold, and from hitting itself while running. Slack belt management has one variable, static tension, which must be carefully monitored, and is higher than necessary to keep the belt on the gears (and possibly leading to premature water pump bearing failure). Running tension varies cold/warm/hot/track hot. The timing belt flaps when cold or is stretched by high rpm running or acceleration.

Or:

A compact system with large steel bushes on all pivot points, a pulley that is one huge bearing with a machined flat surface (wider that the belt), operated by a tensioner/damper which adjusts automatically to slack belt length as it passes by. No monitoring required. Running tension is the same at all engine temperatures. The belt never, ever, flaps.


PKT/PKsn'r/PorKensioner deniers crow that the component parts need to be vetted anew because they are used in a new application. I believed that the first time a 928 engine was run with these parts, and the belt stayed on the gears, the parts previous record on it's native application could be used. Now that the system has shown that it handily outlasts a 928 belt change interval, and can be run up to 7000 rpm (oops), why not upgrade to a modern system? Why do almost all modern engines with timing belts employ a tensioner/damper system? Low/no maintenance and longer service intervals.


Variable running tension will affect cam timing. An undamped, slack belt on the tensioned side from high rpm/acceleration belt stretch, will allow the 5-8 cams to change timing unpredictably.

 

I believe the primary cause of worn cam gears (now $400 each) is the old tensioner system (eg. not adj properly...or lacking oil to allow it to function properly).

Although we don't have the data to support that the Porkensioner will alleviate if not remove worn cam gears from our futures.... I believe we just need more time to prove it.

Just put it on....no adj needed...and change out per Kens recommendations in this thread....