Way OT but............

Had a serpentine belt go on a Chev Deisel truck..............didn't bend any valves but split the high pressure oil lines to the cooler.

Smoke!!!!

Also, raced Ducati motorcycles, cam drive is by belt..............when properly done, all's good to 16k rpm.

Good for Ken in this invention but have to ask; what % of belt failures are due to the tensioner?

As far as I can tell the mechanical part of the Porsche design tensioner is somewhat robust; its the other 'stuff' that fails primarily................no?

 

The tensioner system is taken complete from an Audi engine, so it's already a proven design. The tensioner/damper, lever arm, and pulley are a set. Subsquently, when changing the belt, you would normally only put in a new pulley. The damper is replaced only if it is leaking, as they are designed for 90K+ miles.

This system replaces both the tensioner and the main problem with the Porsche design, the lever arm and pulley. (You can also remove all of the idler pulleys, like I have done.) The lever arm and pulley bushings are made of steel, and are much, much, larger than the plastic 928 bushings. The whole system is much more compact, so there's less chance of misalignment.

The Audi tensioner/damper not only keeps a constant tension, regardless of engine temperature, or belt age, it also acts like a shock absorber, and smooths out the flapping or harmonics in the timing belt. The pulley is the same size as the crank gear, and has a much larger bearing than the 928 pulley. All this means the belt, gears, and water pump should last longer, and I'm imagining it might even add a few HP, with smoother valve timing. It will also be less expensive, with less parts to buy and replace, especially if you like to do the belt change at the 45K(30K!)mile/5 year interval.

The stock timing belt cover fits over the bracket and tensioner, as normal, without cutting. This should replace all 928 tensioners, '78-'95, with one kit.


clic pic for thread

The BELT. TEN. o<O light is annoying. (BTW: I find it odd that you can cancel this warning!) I thought about making some kind of switch to replicate it, but I don't think it's necessary, and there would be a chance that the sensor parts might get into the mechanism = bad. So I'm going to make a ground wire to bypass the light.

I expect the delivered cost will be around $300 for the bracket, bolts, ground wire, and Audi parts. (The Audi parts can be sourced at any auto parts store, but I can get them at shop prices.) Just the bracket, bolts, and ground wire around $100 - you source the parts.

 

I forgot...the air pump bracket will be optional, at extra cost.

 

The thread for those who could not click:

https://rennlist.com/forums/showthread.php?t=277821



tino

 

great work Ken

I cant wait to get one!

 

Why Porsche continued to use the old style washers in oil when the auto tensioner was already being used on the 968 totally eludes me unless they (in 1992) already knew they were going to discontinue the 928 and didn't want to put any more money into any redesign work, other than the minimal. This wouldn't have been that much extra really. Maybe by then they already were using up their extra parts in prep for pulling the plug?

Harvey

 

 

PorKen,
What are the timelines for ready to sell kits? I am down for one! (well in a few weeks anyway after I graduate)

 

Curtis' idea is the one ! A microswitch with normally closed contacts that is set up so that when the tensioner gets to the end of its adjustment range, it goes open contact.

Set this up to trigger on the "belt too slack" limit of adjustment range of the new tensioner.....

 

Nice pic, Curtis. That's what I was thinking.

The tensioner is non-adjustable, it has a self-adjusting range of 11mm. With low tension, the piston extends immediately, with overtension, the piston retracts to a point where tension is again ideal, after ~30-60 seconds. The internal spring would have to fail in order for the piston to retract all the way in.

I suppose I could isolate the tensioner and it's mounting bolts, then ground the tension light through the tensioner.
...

I don't really have a timeline per se. I have to source the different machining steps for price, write a manual, and continue to run the system on my two 928s. If all goes well, it should be ready by spring.

For the brave, I could make a small run of pre-production brackets, unplated, with no manual. But you'd have to be able to install it now, and preferably have a 'non-interference', US 16V. I think I could get 5-10 of those out for around $260 for the bracket and tensioner parts.

 

The pre-production "beta" testing of 5-10 samples would be an EXCELLENT real-world shakedown, especially if you get a cross-sampling of different 928 MYs. Nowadays, car manufacturers will not release anything that hasn't endured thousands of miles of real-world testing on multiple samples. Toyota builds beta fleets of cars, hundreds of them.

There are many brave people here, I'll bet. I would pony up to be a beta test car if I had one at this time.

 

When you get around to the 32 valve beta group count me in. I have at least as much faith in your design as I do in the Porsche solution and because I think I'd like to change my TB and waterpump with all related components soon anyway.
They were put in new around 20,000 miles back but it was back in 2001. I'd like to know, first hand, what's in there and that every part was replaced and it was done right.
So for me, it would be wrong to not go ahead and make the upgrade to your design at that point.
I'm willing to roll the dice....
One thing I haven't heard anyone mention is, what is the history of the tensioner you chose? Volvo I believe, does it have a good track record? As long as it's a good choice I have faith in the work you are doing to get it mounted properly!

 

Ken............count me in also as part of the beta test group

My TB and waterpump are on the winter project list and if possible don't want to throw money into the old tensioner if your solution is available before............April?

 

dont think there would be a 32V beta group.

The idea of doing it on 16V cars is cause if it does fail after said miles, there is no internal damage, only refitting and realigning the cams and going at it again. I think Kens idea is great to run them n 16V cars, iron out all the problems, there are bound to be some albeit probably minor. then when durability testing on the 16V models shows they are good, sell them to the 32V owners as well.

Of course if you want one now and have a 32V car I am sure they are fine, but if a problem arises then you have a substantially higher risk then the 16V guys. You will need to pull heads if they fail on 32V engines.

 

from what i remember the tensioner and roller is an audi sourced part from their V6's?????