SeanR

Considering that Porsche put a warning system should tell you something about their confidence in that system. To this day how many millions of cars with belts have a belt tension warning system?

Edited for dumb stuff.

Bill51sdr

+1 Some of you doubters need to take a look at a Toyota 4.0l V8, have a look underneath the timing covers and get back to us with what you see there. It will look very familiar with the exception of the tensioner system. That's just one example...

Bill51sdr

The warning system will not save you from sudden, catastrophic failure of the WP bushing & resulting belt slackening. It happens and the belt tension warning light has the same relative value of an "idiot light" in that situation.

IMHO, take that for what it's worth the theoretically lower tension the Porkensioner applies to the belt probably extends the service life of the water pump... theoretically that is. Mine's been on there a couple of years now & others have had theirs longer. Knock on wood, but we have yet to see any dire threads accusing a failed Porkensioner of destroying an engine. Considering the history of these exact types of tensioning systems on other manufacturer's engines, I don't think we will. Hell, Porsche put the same thing on the 968 engine. .

Landseer

If you maintain them, the originals work fine.

The new version is great. Be sure to remember to replace the tensioner on the new version, though.

Our 84 Euro, questionable if interference (but assume it), has 5 years on its PTensioner and Conti TB.

Might be time for Gates belt and new tensioning module for the PTensioner?

There were some data points consistent with above post, too, that the PTensioner was easier on the system, specifically the expensive timing belt gears.

Either way, you are good. If you pay attention to the details.

polcan

Hi all
My saga continues.Now i know why my belt was rubbing.tensioner carrier was put on such a way that only cam cover was holding it in place.Washer(#45) on screw #5 was missing and whole carrier can slide back and forward as it pleases ,even passing screw #5.Belt was hold in place by shaft trust washers.Even tensioner pulley was put back wards.With washer #6 in front and only nut in the back i pulled pulley out of carrier with nut still on it.God damn!!!!!!!!!!!

polecat702

I'm running Ken's tensioner, and Ed's Guardian water pump. Both work great! Vegas summer should be the real test for the pump, I'm confident it'll be just fine.

Prolly going to be changing over to waterless coolant too. Waiting to hear what Randy Ema, has to report on it in Duesenberg engines.

Adamant1971

Just get a portensioner and be done with it. Glad you caught it before you bent some valves. Count yourself lucky, very lucky.

Bill Ball

Greg Brown did some testing and found the Conti belt stretched almost like a rubber band (belt tension not increasing much as you adjusted the tensioner beyond a certain point), while the Porsche belt did not (the belt tension increased as you adjusted the tensioner ). I'm not sure if he tested the Gates belt specifically but since the Porsche belt has Gates branding, I've extrapolated that the Gates are OK. I had one Conti belt on my car and it lost a lot of tension at 25K miles. No problem with Gates belts - never had to retension one ever on my car, and I've personally put over 180K miles on it. Any time you have to retension a timing belt, I would change it. They should not stretch or wear significantly during their 60K mile recommended change interval. At the prescribed 1500 mile new belt tension check, you should only find a fractional loss of tension due to settling, never enough to trip the warning system IF the belt was properly tensioned. If the warning light ever trips, I'd want a new belt unless the warning is not due to low tension.

PorKen

Free Belt Length between the crank gear and the 1-4 cam gear changes with engine temperature and rpm.
FBL is what is left after the belt is pulled taught between all of the gears. It is discharged by the crank gear and is fed to the 1-4 gear.
As the engine grows with temperature, FBL is reduced. At high rpm, FBL increases as the belt is stretched pulling the oil pump/cams/water pump.


The stock tensioner system pre-stretches the timing belt in an attempt to control FBL.
The limitations of tensioning led to all the many additions to the stock system over time - guide pulley(s), warning light, etc.

Tensioning is an inherently flawed concept for dealing with FBL as it only limits the range of FBL - it does not directly manage FBL.
In order to reduce the stretch range over a large temp differential, stock belt tension is high, reducing bearing life and wasting HP.

Tensioning may work well enough with a small displacement 4 cylinder engine, but not on a large V-type engine. (Gates tech bulletin)


The PKT is a belt management system, reacting in real time to FBL, using only enough belt tension to keep the belt on the gears.
Properly managing FBL keeps the belt flat against the crank and 1-4 gears so they always have maximum belt wrap (of the narrow 1" belt).


Note the 968 was upgraded to a PKT type system when variable cam timing was introduced and the engine was englarged to 3 liters.


The Gates Racing belt has virtually no stretch at all.
GB noted that the Racing belt probably could not be used with the stock tensioner system (as it cannot be pre-stretched).

When doing a 32V'r check on a Racing belt, I have seen no difference in cam timing between #1 and #6 at 0° or 45°.
With a regular belt, there would normally be up to a 2° difference because of differing amounts of valve spring pressure.
No stretch is good as the cam timing, cam to cam, cam to crank, won't change unpredictably at different temperatures/rpm.

928 at last

If you've got the invoice for the last TB job, what shop did the work???
We need to know to avoid someone else not being so lucky the next time around....

928 at last

Mind you, Not that I would be using a shop for that.....

Imo000

The warning system saved me from exactly that. The pump pulley stopped, the belt started streching from the friction of the stationary pump pulley the light cam on and so did the exclamation light. I've noticed it and cycled the ignition but the high temp warning came off as soon as the ignition was back on. Shut the engine off right away and coasted to the shoulder. Popped the hood, pulled the intake tubes to see the belt and only then I was able to smell the melting of the timing belt. Once it was all apart, it was clear the belt was seconds away from snapping. The belt warning system was the fist indicator that something was wrong. I beleive it gave me enough time to be alert when the temp warning came on. This is my first hand experinece and not some theory. But there are others that weren't so lucky and choose to ignore the belt warning and paid dearly. I like and preder the facotry system because it saved me once.

John Speake

So how much piston movement is there dynamically as the belt rotates and the loading on the belt varies ?

PorKen

Piston travel can be as much as 2 mm after starting cold at idle.
Cold cylinder pressure is unequal for a time, accelerating the crank at different rates.
It barely moves at all at idle when warm.


For a PKT warning light, two positions would be required for a switch/sensor.
Fully retracted is a failure where free belt length is unmanaged. EG. tensioner/damper failure.
Fully extended is the situation Imre fears, where the belt is stretching out of control, or a pulley is falling off.

Mongo

Here's another example - Ferrari 355. Are those hydraulic tensioners on there too with no wires indicating a loose tension warning??? *sacrasm*