blown 87

I do not see a chance of that being possible at the proper tension, 5.0-5.3 is tight, real tight.

I am running one of your tensioners Ken, so I do have a idea about them.
Not sure who has the most miles on them yet, but I am at 12,000.

Lizard928

I had around 30k iirc on one of mine before I pulled that motor.

rexpontius

FWIW I am running a Pkensioner on my 86.5 and checked its behaviour many times. The system seems to work perfectly, at all times, hot, cold, accelerating, etc.

Much, much, better than the Alfa Romeo 24v factory tensioner design I worked with a lot.

Do not see any need to fit a stronger tensioner piston.

GregBBRD

If you run a belt with a stock tensioner at 3.7 or lower, the gears wear at an alarming rate. I guess once you some feedback about what the gearwear is when your tensioner is used, that question will be answered.

PorKen

The stock (de)tensioner cannot manage the slack belt length at low static tension. Too much belt is what creates wear as it flaps around the gears when the engine decelerates.

The Audi tensioner/damper adapts to the belt length needs of the engine while running, so it doesn't need to have the belt under high static tension all the time.

PorKen

Here again it's about belt length, not tension.

As the engine heats up, the aluminum expands, the cams get farther apart from each other, and the crank gear. The number of belt teeth cannot change, so the cam gears are pulled CW toward the crank, advancing the timing. Following the belt, it's a looong way from the crank gear to the 1-4 gear so it is advances much more (~2°) than the 5-8 (hardly measurable).



I have it on my mental checklist to try and check the cam timing as the engine is running with a timing light through the breather pipes. I'd like to see how much/if the timing changes at different rpm versus how they are set statically.

Z

I checked the change in cam timing from cold to warm while idling with a timing light on my car a while back. The change from a completely cold to completely warmed up engine at idle was the cam timing advancing by 3 degrees. Both banks changed by exactly the same amount. I did this several times, and the results were always exactly the same every time that I did it. This was on an S4, with a stock belt tensioner in good condition and filled with oil, and a properly tensioned timing belt that had been on the engine long enough to go through the initial stretching that new belts go through.

One of these days I'm going to log cam timing to see the changes at different engine RPM, loads, and in different gears while under full throttle acceleration on the road.

Lizard928

Ken,

Use the S4 hall sensor, and log it with the RPMS. You should be able to log the change that way.

With responce to Greg's comment about cam wear.
The motor I had around 30k on was run with no cam covers (32V S3 motor) running MS.
It had many track miles, along with hard street miles. Driven in temps as low as -45C.
On sanded/graveled roads. Etc.

My cam gears (were new prior to this abuse), showed ZERO wear.

I have seen many low mile cars with the factory tensioner with cam gears that need to be change.
These range from one with 14k original KM, to others with 65k miles (Terry GT). All previously with the factory tensioner. When I checked them they all seemed to have the proper belt tension.
Granted I do not have the factory tool, as I would rather spend my $500 elsewhere.

However I am very curious as to how you have measured the belt units with the Porkensioner?
The reason I ask is due to the fact that if you put load on the belt with it attached it will compensate for this.
Did you possibly anchor the pivot once the setting was made so that it could not retract at all?
As I for one would really like to know how your imperical data was achieved.

GregBBRD

This is an exact example of why I don't use your system....you rave about how great it is and how uninformed I am, but you still have things on your "mental checklist" that should have been done from the very beginning during testing. How can you possibly not know this?

PorKen

Thanks for the info!

I wonder though, ignition advance changes with coolant temp. Did you compensate for that?

I'd need a S4, then? :P

GregBBRD

Rob Edwards had a Porkensioner that he wanted me to install on his stroker engine. I've always thought that the stock tensioner system worked pretty darn well. As a matter of fact...when Ken anounced that he was building a "better tensioner" Mark Anderson and I talked about it...and we both asked "Why would anyone build a replacement tensioner system for something that works so well?"

Anyway, I agreed that we would bolt the Porkensioner onto Rob's engine and study it, which is what we did, while it was on the stand. We simply recorded the furthest point that the tensioner reached while turning the engine over. We then held the tensioner at this position and measured the belt tension. So, 3.7 is the tightest that the belt can get with this system. Note that the tensioner compresses from this position, while turning the engine...so there are times when the belt is much looser. This means that this tensioner allows the belt to fluctuate in tightness, which means that the cam timing is jumping all over the place.

We installed a stock tensioner and checked the belt at various positions...there is no variance in tension, as we turned the engine. Cam timing is locked down and consistant.

Rob gave this Porkensioner away to someone....

Rob Edwards

Well, actually, I ended up selling it back to Roger, who had sold so many he didn't have any in stock at the time.

I do have a Porkensioner on the GT, no problems whatsoever so far . Of course, there's also a remanufactured Laso WP on the GT. Ticking time bomb? Maybe. No mechanical thing is 100% reliable forever. I've got a lot of spare valves, and the headgaskets are gonna need an R&R eventually anyway.....

As far as the stroker goes, it's Greg's engine as much as it is mine, and if he's more comfortable with a system he's laid hands on for 30 years, I defer to his experience, simple as that. Besides, for an engine that cost as much as the car, I'd just as soon at least have a warning light on the dash (though my skillz at ignoring warnings are perhaps better than they should be....)

Whether the PKsn'r is an improvement or not, I think that Ken has brought immeasurable value to the 928 community, as have many other innovators who actually followed through on a(n arguably) better idea. I wish I had the brains to make such a contribution. But there's never been a better time to be playing with these cars, I think we need to keep reminding ourselves of that.

PorKen

Let me restate the obvious: I am curious to see how much/if the cam timing changes at high rpm with any tensioner system.

This is a good example of why I find your posts to be increasingly irrelevant.

Problems with the stock tensioner system have discussed ad nauseum on this and other forums for years.

There had to be close to a hundred installations or more when MA emailed me to see if he could sell PKsn'rs (and 32V'rs). It was already proven. He said that you had some questions, which I answered. I never heard anything back.

Your failure to see the benefits of my design has made Roger a lot of money.

3.7 was the tightest you measured by turning the engine by hand. At no point did you turn the engine with the starter or run the engine.

You really have no business talking about things you (still) don't understand.

As has been said many times already, the cam timing doesn't change when the 32V'r is used properly, whether using the stock tensioner or a PKsn'r.

Z

Yes. The first measurements were made immediately after starting a completely cold engine. Measurements were then made as the engine was warming up, and when the temperature of everything had stabilized at their normal operating levels. You could easily see the cam timing changing with increasing temperature until it stabilized when the temperature did.

If not an S4, you could add a sensor to the cam sprocket of an earlier car that doesn't have a factory hall sensor. There'd be various ways of using different kinds of sensors, but I think a painted or tape stripe on the sprocket and an optical sensor might be easiest. That and a crank position signal to reference it to would allow you to do it.

Lizard928

Actually ken you can add the ring and S4 backing plate with sensor attachment to the S3 head...