SeanR

Hilton, I'd not let that bother you.

We are the only ones that have a belt warning system and that is due to a poorly designed tensioning (de-tensioning) system. I used to have the same worry until I started to play with them. My bet is had Porsche kept up development on our cars, they would have gone similar as they did on the 968. I may be wrong, but just my thinking.

BC

What if we already put in the plug? Whats the issue? Looks like it would work just fine.

SeanR

If it's working fine, don't bother changing anything. A few of us have had them leak due to a not so tight fit.

PorKen

It's a dandy.

Functionally the same as in the first photos in this thread, but lighter in weight, easier to make, and oh so stylish. (This will likely be the last revision.)

SeanR

I know which I'd rather have on my car.

RCinXS

Glad I happened upon this post.

The plug spun right out taking the silicone with it. It would have most certainly have leaked sooner or later.

Will pick up a 8mm SS Button head and copper crush washer and install it.

Tony

The warning system ONLY tells you about belt tension. Nothing else. Belt tension is set by the PKensioner now so its a non player as far as warnings go.

Like ive said before the belt could be coming apart, but if it still is at the correct tension you will never know about it with the stock set up...until it snaps

SeanR

Very good point.

This is the GTS I put the above PK tensioner on yesterday. Take a look at this belt. Had already shredded off 1/8 inch. Inner thrust washer missing



The bushing was missing on the front of the tensioning arm making it worse.



Two bolts missing from the stock one, idiots. The belt was done 2k miles ago.



Now all is good.

Hilton

Completely agree in the stock setup - however there are enough anecdotes here about the warning light coming on as a result of the belt degrading rapidly (e.g. cooking itself on a seized water pump pulley) and the engine being saved.

Frankly, I'm not concerned about the belt failing and losing tension - I keep a regular maintenance schedule on all my 928's and replace all the wear items. I can't think of any incidences of belt failure other than early non-intereference 928's where the driver deliberately doesn't care about failure and drives until it goes.

My concern is failure of a cam sprocket, belt roller bearing, water pump bearing etc. - which can cause immediate and rapid belt degradation. Even a 10s warning on the belt coming apart as a result of such a failure would be enough to save the engine. When I'm ready to do my 89's next belt replacement (probably later this year - a little early but I'll be swapping cams anyway) I'll look at adding a switch and installing the Porkension'r. I have no qualms about its ability to manage tension, I've owned a couple of V6 Audi's with the same tensioner - I bought one of Ken's second batch, back before Roger started selling them. I just want the peace of mind that goes with the added security of a warning light.

In the case of the Audi tensioner - the warning light won't be a warning about belt tension, as the tensioner should take care of that. It'll be a warning of tensioner extension indicating its trying to compensate for a failure elsewhere in the belt system.

Our cars are all aging - the chances of age-related wear on other parts of the belt circuit is increasing - e.g. cams have had 20 years worth of harmonics and stresses to work on any casting flaws. Any added insurance on the original engine remaining intact is a good thing in my book.

I'm happy to be convinced otherwise - thats why I'm posting it in this thread, because the warning system lack is my only concern. I've seen one installed while helping a friend with their TB job on an 83, and examined my own bracket and bits carefully and the quality is excellent. Plus I've installed the same tensioner on its intended use on an Audi 30V V6.

Landseer

Jim pre-emptively replaced the H3 cylinder on his Perl white car yesterday, as it was down for a new WP and Gates belt. That piece has a certain life expectancy on Audi cars.


We consulted an Audi master tech for his opinion and he suggested early vs later replacement based on his experience with the 6 cylinder application and the downside risk exposure.

We, too, have another one that dates back to '08 on Jim's old Euro car. It will get a new H3 this fall when it comes in for the next service.

Like Roger and others have pointed-out, the cylinder (hydraulic or spring loaded or whatever it is) doesn't cost much.

The question is, should petrol still be available a few years from now, will others remember to replace the H3 cylinder? On another thread somebody suggested (with a boosted car) that they expected 100-150K miles before replacement. I think that's too long.

I have no data to suggest the correct interval. No experience with failures. The automatically tensioned system seems great. Huge positive energy around the unit. But we are remiss if a label isn't stuck inside the engine compartment suggesting the service interval. (opinion)

SeanR

For me, each belt change I will change the piston each time, it's cheap.

dprantl

I would think replacement every other belt change would still keep the risk to a minimum.

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

dr bob

My thinking on a warning system replacement is that it would be OK to use tensioner position vs tensioner tension as the original used. If a belt is damaged, or a drive component is damaged to the point where the belt starts to get longer, it would set the belt alarm light. But it isn't really that simple... With the block cold, the tensioner piston is extended, and retracts as the block expands and the distances between cogs gets larger. To use a position-based alarm, it would need to consider temperature. It almost needs a bimetallic arm attached to the roller bracket, actuating a limit switch, contact, or maybe an opto-interrupter of some sort. Needless to say, getting the initial setting right will be a challenge. Plus it would need to be re-calibrated after any normal/expected initial belt stretch.

Hilton

I agree - finding the point at which the warning doesn't false-alarm, but is still useful advance warning will be trial and error.

I have a used timing belt which is already stretched that I keep around for setting cam timing - I figure setting the arm on the pivot so that it activates at 1mm of extension greater than a cold engine with a stretched belt will be adequate, for *that* specific vehicle. The belt warning system doesn't activate for 3 minutes which gives a little time for the block to start expanding and retract the piston, to provide a little more clearance for any harmonic "flapping" which may occur as rpm's change.

Wear on other items like cam gears etc. will affect the extension too - some old posts about piston extension indicate some have found as much as 8mm of piston extension on cars with worn sprockets on a new belt. The total piston travel is 11.5mm - so those which were 8mm on a new belt may see as much as 10mm cold once the belt has stretched.

Oh well - its all hypothetical at this stage - I have too much else on my plate to fiddle with installing it and modifying for my 89 just yet A solid modification with warning will need a fair bit of time measuring running time/temperatures/extension on new and stretched belts, and possibly worn vs. new cam gears.

Once I do get to that part of my 89's job list (it'll be 5 years next June - which in my book is time for belt replacement), I'll start a thread about it and include a lot of measurements of piston extension, engine running time, temperature etc. As I say, I'd like to run a Porkension'r for the belt management side, and intend to at some point, when I can sort out the warning system issue.

borland

The warning system is needed because the factory tensioner requires a delicate belt adjustment. With the self-adjusting PKsn'r, the warning system is no longer necessary.