Imo000

Yes, yes, I know. That's not what I meant. Porsche made one tensioner of each variation. For example, all tensioners for the '87 are the same. This part works for all the engines that was released for that model year. They didn't have one that worked for most of the '87s, it worked on all of them. That's my point. If the Audi tensioner is supposed to work on all stock 928s but it doesn't then the design parameters of the product are wrong.

Hai gebissen

But...why? The factory roller hardly ever comes into play (apparently), but if it does, it prevents what it is meant to prevent. It hardly weighs anything.

Imo000

I'll get you the shop's number from Danny and you can discuss the steering rack with them. I'm only replacing it. As for the tensioner, don't worry, I feel perfectly comfortable working with it, regardless if I like it or not and will stay on the car. Now having said that, the one on there has a cadmium finish and the bolts don't look like the one in the black edition. Is it safe to leave it there or does it need to be retrofitted with the updated hardware? I would also Ken, I mean Porken, but he black listed me.

j.kenzie@sbcglobal.net

It's a free of charge kit, if you call Roger. Why not do it?
Dave

jcorenman

There is already a "ratchet" on the tensioner to limit reverse travel, so I think the engine kicking backwards on a backfire is a non-issue.

Remember that the tensioner is a spring, piston and check-valve, so it extends quickly with the spring pressure (more when the rod is compressed, less when extended). However when the rod is compressed (e.g engine kicking backwards) the check-valve is closed and the compression rate is limited by fluid leakage around a tight-fitting piston.

Put a tensioner on the bench, rod-end up, and whack it with a hammer. It won't compress. Stand on it and wait, and it will slowly compress.

The trouble with over-extension, besides the potential for running out of travel, is that the spring force gets weaker the farther out the rod extends. And friction in the lever assembly adds to that.

jcorenman

No, it is not safe to leave it. The problem is that the older "gold" brackets were countersunk with a 5/8" SAE 82-deg countersink bit, while metric M8 flat-head machine screws have a 90-deg angle. The result is that the fastener makes contact only around the edge, which increases the bending moment (which is aggravated by the oversized 9mm thru-hole for an 8mm fastener).

The PKT hardware kit includes a special flat-head fastener with M8 threads but a 82-deg countersink angle to match the bracket. This is the retrofit for the "gold" bracket.

The "black" bracket is countersunk with a proper 90-deg bit and uses a standard M8 flathead. The other alternative is the one Colin mentioned above, re-drilling the countersink on a gold bracket with a metric 90-deg countersink, and using a standard M8 flathead.

I hope this helps.

PorKen

While the 82° countersink is not ideal, it has not proven to be a problem, except in Jim's mind. All flat head bolts have been found to be tight. He knows this. And, the through-hole 'problem' is in fact not a valid issue.

Jim enjoys finding problems that could happen on paper, but don't in the real world. He should try his hand at creating unique 928 products, which I'm sure would be awesome, on paper.

jcorenman

Ken, why do you always respond to technical facts with personal insults?

Is anything that I said incorrect? If so, I would be happy to correct it.

j.kenzie@sbcglobal.net

Agree the countersink degree difference should be insignificant. Maybe actually an advantage.
Dave

PorKen

My mistake, JC Real World Products would undoubtedly be unbelievably awesome.

He would surely send you an unsolicited email and/or post about it to tell you why.

jbrob007

OUCH! So I take it the gold PKtensioner should be fine until it's time to change the timing belt again and then make the upgrades?

PorKen

FWIW, I have not changed the ones in my 928 'fleet', which all have gold brackets.

Truthfully, the special bolts were a 'feel-good' measure. But if it makes you feel good, please accept a hardware update pack, with my compliments, from Roger.

The lever and pulley through bolts are better all around. I would like to change those eventually, myself. The threaded holes to use the bolts which came with the INA parts was again a nod towards an easier installation.

jcorenman

Ken, (May I call you Ken?)

Why do you always respond to straightforward questions with personal insults?

Seriously: If something I posted was incorrect, I will happily correct it.

jbrob007

Thanks for the reply. I'll worry about it when the belt needs replacing... Considering I put about 20K miles on a 928 a year I figure that time will come soon enough

docmirror

That is doubtful. Aviation countersink machine screws and rivets are matched to their countersunk hole. Typically 82deg or 100deg depending on the parts joined. There are literally billions of matched hole countersunk fasteners in the aviation world. No one would allow a mismatch in countersink to fastener.

However, in this case I have no idea of the potential for it working loose, but in the aircraft world, it would not be allowed.