jeff spahn

Yes Rob but I think RKD was alluding to a situation where he felt the warning system was actually doing something that could have saved him had he left it connected.

Any warnings he was getting with the warning system while having the Porkensioner installed were in no way related to the cams breaking. The cam breaking would still have happened and the warning would simply have been another indication beside the car dying that something was wrong. So you'd basically get a 1/10 second advance warning of the front of the cam coming off then your car would still die.
I can't see a scenario where the belt warning system would have given you any hope when the front of your cam comes off. That thing breaks off and your damage is done.
A visual inspection, factory tensioner or porkensioner aren't going to save you when a catastrophic failure happens.

dprantl

Although there has been a documented instance here of such an event, I think the chance of the stock tensioner warning system saving you when something catastrophic happens, such as the cam breaking or the oil pump gear coming loose is very small. Like Jeff says above, in most instances there will be so little time between the firing of the warning and engine damage it won't prevent anything anyway. We are taking about catastrophic failures unrelated to the tensioner itself, but due to some other issue. And on cams breaking off at their noses, this may actually be happening due to the belt being too tightly tensioned at one point in the car's life (which cannot happen with the porkensioner).

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

69gaugeman

Many untruths in here. The belt tensioner warning will ABSOLUTELY give you enough time to prevent disaster. It has been documented here MANY times.

IGNORING the message or not properly checking for a problem is what causes the damage.

Even in my case if I had towed the car home and taken apart the front end, I would have found the migrated oil pump gear and would have saved myself a top end rebuild.

Use the stock stuff! It works.

jeff spahn

So do wooden wheels but we have moved to more advanced wheels now and are better off for it.

In some cases, perhaps like yours, it will save things. In the aforementioned instance of RKD, I doubt it.

Remember we are talking about the failure of the cam when the front broke off.

You aren't going to get a warning telling your the belt is loose. The cam breaks and then freewheels. You have to put the car in neutral and then stop the engine all within 1 revolution.

No warning system is going to let you do this. His failure wasn't predictable by a belt warning system. It was catastrophic.

I doubt even this kid, as fast as he is, could put the car in neutral and stop the engine in 1 revolution.

PorKen

I am going to be testing [this PKT warning light mod] out when I downgrade to a regular Gates belt, soon.

(I want to see if there is a difference at high rpm cam timing vs. the Racing belt I have now.)

RKD in OKC

I had the stock belt tensioner with it's stock warning setup. When Sean did the valve job on my car he asked me if I wanted the Porkensioner. I said not if it disables the warning system because the warning system would have saved me a valve job if I had know to look deeper for the reason it went off. The vibrations of the cam getting ready to break set off the toothed belt warning. In other words more than just a loose belt will set off the toothed belt warning. That's why I wanted to keep the warning working.

Lizard928

I think some of you are looking at this all wrong.

How many cars (in history) that had timing belts (not chains) have a warning system?
How many of them experience failures when proper maintenance is done?

So long as the proper intervals are taken and proper care is done, the chances of a failure is very small.

We also have 2 people on the board who have said they got the warning light, and still had the failure!

I've seen two local members who had the stock warning system and had the waterpump nearly fail on one, and seized on the other. Neither of them got warning lights on the dash. Both of them avoided a problem by hearing noises or seeing a coolant leak and turning off the car.

The amount of people that the warning system has saved has probably been extremely few.
Most who see it tend to just ignore it instead of doing a full tear down. And I doubt that had the cam gear been taken off of RKD's GTS the problem with the camshaft would have been spotted. Most don't look that deep for the minute hairline cracks that would have been there, then BAM complete shearing of the camshaft.

RKD in OKC

Beg to differ. One of the 3 prongs on the hub the cam gear mounts to for timing the cam was cracked long enough that the crack itself was rusted and there was a line of rust where the crack was touching the back of the gear. When it finally failed that prong on the hub was gone and nowhere to be found. If the gear had been removed after the first or even second toothed belt warning where the belt tension was correct then this crack and wear around the keyway would have been found and parts up to and including the cam would have been replaced eliminating the issue that caused the end of the cam to break off. The car had 60K hand had the timing belt replaced and the tensioner rebuilt 15K before the end of the cam sheared off at the end of the keyway for the hub.

I'm not saying the warning will catch every problem that will cause a valve crash, but it does warn for more than just belt tension.

Lizard928

Uhm, the belt tension is the only thing that trips the light.
It is tripped when the tension drops below 4.1 iirc on the factory gauge. As below this tension the contact breaks the ground signal.

So your last statement makes not a lot of sense......

depami

Static tension versus dynamic tension. Other problems throughout the valve train could cause decreased dynamic tension at the adjuster that wouldn't be seen on a static tension check. The porkensioner will mask these dynamic variances.

RKD in OKC

A belt will still deflect enough to set off the warning even when under the proper tension given the right circumstances. The combination of the length of the belt not supported by pulleys or rollers, rpm, heat, and engine vibrations at just the right frequency can set up a harmonic that would vibrate the belt like a piano string. That harmonic vibration can have enough amplitude to set off the warning.

When my tensioner was loose, the light first started coming on just sitting at idle after the car warmed up. The tension checked within range.

When my tension warning was first coming on before the cam end sheared off it only came on when lifting the accelerator at high speeds. It did NOT come on if I accelerated and lifted in lower speeds and gears in the same rpm range. Even after it had come on at high speed. AND when if first started coming on the belt tension checked well within range.

69gaugeman

If you put pilot sports with HRE racing wheels on a donkey cart, the cart performs the same . No point in putting new technology where it doesn't help. The tensioner is PERFECTLY fine in the application it is used in.

ALL of the failures I know about were because the warning was ignored.

This. Like me the warning was ignored. The result is the same.

100% FOR SURE THE PORKENSIONER WOULD HAVE BROKEN THE NOSE OFF WITHOUT WARNING.

Not being saved as a factor of ignorance is not a failure of the system. But you brought up an important issue and that is regular maintenance. With regular maintenance the system never even gives the alarm.

Hell even in my Audi's and Touareg , I check the belt. Maybe every six months or a year when I change the oil. 30 seconds to pull off the cover and see the belt and how it runs.



And it keeps the belt tensioned and it fits in the existing spot and doesn't require money spent on new components. These are reasons enough for me to keep the stock tensioner. It works. Plain and simple. And I have and have had MANY Audi/VW products with the Audi tensioner system. They break belts too......

SteveG

Trying to track down whether RKD's light is on and when, and whether he had Porken and defend my "assumption" uh, oh. not a big deal, but . . .. and quoting RKD, from this it appears he HAD Pken, but later says he told Sean he didn't want one. At any rate, "back" implies he had Porkensioner. RKD is not a newby so I (uh oh) assumed he (or whoever installed it) followed Ken's instructions. I assumed, my bad.

He and "whatudrivin" also said it was coming on while driving, not 3 minutes after start.

jcorenman

No, stock tensioner, from post #21:

the flyin' scotsman

Has anyone on Rennlist or otherwise had a 928 belt failure because of the Porkensioner? I haven't read of any but I don't read everything.

A camshaft break with the OEM tensioner was caused by? A belt break when a water pump seized wasn't a tensioner issue but the time of a warning light might be the same as the noise of the screeching belt for reaction time.

There's less parts involved in the Porkensioner therefor less parts to fail. The parts that are in the system are more robust than OEM.

Don't believe Ken said install it and forget it for ~60k but to do periodic inspection.

If folks want to rebuild the OEM unit and live with its faults so be it.......each to their own but hate to break it to you......the world is not flat!