bureau13

I don't think that's true. Interference engines are quite common these days. I tried to look it up once and it was a pretty long list.

mark kibort

how much does the tensioner adapt to he engine growth at temp? if you were set at "3" on the guage, would it grow to a higher tension, say , "5" (rated tension) if the tensioner was a fixed bar.

hacker-pschorr

You would have a hard time finding any engine that is not interference these days, or any period over the past 20+ years.
Every Audi I can think of since 1990 has an interference engine. Even the **** poor slow 3 liter V6 from the 90's.

GregBBRD

I consider the idler arm and associated pieces to be part of the tensioner, of course.

Still have never seen a failure, no matter how stupid the previous mechanic was.

That being said, I'm certain I've "redone" more belt/tensioner jobs at very low mileage than I've started from scratch. I find the mechanical ability of many professional mechanics alarmingly low...I'm not going to even talk about home mechanics!

I'd agree that that thing that Ken makes is easier for the complete idiot.

ROG100

I object as I resemble that remark 8>)

kmascotto

Not belt driven...current interference engines are chain driven. Which will likely last the life of the engine.

Alan

I think there are still plenty of belt drives out there in current vehicles and most are interference engines.

Alan

karl ruiter

I had three cases where problems with the stock tensioner caused me grief. Not sure they constitute a catastrophe, and they were at least partially my fault, but still I'm done with the stock tensioner.

1) I installed a Conti belt in my '82. The belt stretched and I was not watching the tension closely enough. It lost tension, damaged the cam gears and skipped a tooth. I think that at the time rennlist did not exist so I had no way to know that Conti belts would do this. GB would never have this issue as he would have only used Porsche belts.
2) I purchased a used 928 (my cab) and put a water pump, belt and the pullies in it. But I did not replace everything and there are some plastic bushings in the system that were worse than I thought. One of the plastic bushing failed, the system lost tension. I don't remember what the damage was, but probably the same thing. Again GB would not have this problem because he probably replaces all the parts every time.
3) This one really is my fault. In the days before the Kempf tension gauge existed and the days before rennlist I bought a 928 that had been hit on the left and one cam broken. I replaced the cam, but did not have any way to adjust the tension correctly. I could not afford the $500+ factory tension tool and there was nowhere to borrow one and no alternative. So I guessed. And had the new cam break with 500 miles.

So, while the stock tensioner may not catastrophically fail, it can fail enough, and it will not help you out if anything else goes wrong resulting in a change in tension. If you are a perfectionist like Greg it is a fine system. Replace Everything Everytime with new Porsche parts and do it on schedule. If you are a little more sloppy or may not hit the maintenance schedule exactly or do not always use Porsche parts you better go for the more forgiving system.

hacker-pschorr

I don't know where you are getting your information but it's not true.

ONE example, the 2.0 Turbo from VW / Audi has a timing belt and is an interference design. This engine is used across almost the entire model line.

Many of the VW / Audi diesels are belts too.

The life of the chain is irrelevant, it's the guilds that matter. Just like a timing belt, we don't worry about the belt, we are concerned about the water pump locking up and snapping the belt.

Chains are great from a marketing standpoint, people think they are better due to paranoia with belts. Problem is, when the chain system fails (and most do) it costs a lot more to fix than a simple timing belt service.

My local shop has an Audi V8 on the bench right now, had to pull the motor to update the chain guides and the engine has less than 110,000 miles on it. A life of timing belt jobs would cost less than what this service bill will be.
It's not a fluke either, it's not the first one he's had to do with similar mileage.
The service write at he Audi dealer said he's giving out multiple estimates per week for chain guides services.

On top of all that chains flex and stretch, which effects cam timing.

PorKen

Wear can come from a loose belt, too.

That's the thing, AFAIK, no one has ever measured the (alleged) range of the tensioner stack, cold to hot, the composition of which did not change when the static tension (aka pre-stretch) was increased for the 32V engines, increasing the stress on the washers.


Except when GB did use a Continental timing belt. And skipped time on a cold start (allegedly w/backfire).

Note this is not the fault of the belt (note Kibort manages to race with a Conti). It is a failure of the stock tensioning system design which cannot 'take up the slack', no matter how fresh the parts, or how finely the static tension is measured.

GregBBRD

You suppose every one of those engines uses the same exact tensioner element or is that element engineered for the individual load and leverage of each engine?

I wonder how many of those engines mount that tensioner on a crack prone adaptor made from a chunk of cheap mild steel?

Tens of millions of miles on the stock stuff....never cracks, never breaks.

Yes, if an idiot adjusts the belt improperly, there may be premature gear wear. Yes, if an idiot doesn't replace wear items when the belt is serviced, there may be increased wear. Yes, if an idiot doesn't spend $5.00 and replace the pin on the idler arm that is in single shear (on the early cars) and tightens that pin with an impact, it could break.

However, the same things are going to apply to Ken's thing. It's got lever arms in single shear. It's got bushings and pieces to wear out. Get 150,000 miles on it and it's going to need all kinds of repair....if it doesn't crack and fall off the front of the block before that. (Keep in mind that Ken's thing is made from mild steel and is bolted to an aluminum block with completely different expansion rates. Your alternator bracket made from steel? How about the power steering bracket? A/C bracket? Air pump bracket?)

I'll keep the ultra reliable belt warning light system, thank you very much. I've worked on these things long enough to know exactly what that light is telling me. That light goes off and you know you have a problem....how it lights and when is the important thing. If a customer calls me with a tensioner light that just lit, I know exactly what questions to ask! I know if I need to schedule in a belt inspection and tightening, or if that customer needs to call a tow truck. If some idiot can't figure it out and the engine blows up....that's not the tensioner's fault. That's the idiot's fault.

Of the thousands (literally thousands) of 928s that I've worked on, I've had one belt failure that wasn't caused by a bad water pump or some idiot leaving something loose.

One belt failure!!!!!

Use the stock pieces. When the belt is due for replacement, replace the other pieces that are wear items, also. "Rebuild" the tensioner (replace the boot, adjusting screw, internal o-ring, and clamp so that it doesn't leak oil. Use a Factory or Gates timing belt that isn't a giant rubber band. Adjust the belt properly. Re-adjust the new belt at 2,000 miles and every 15,000 miles after that to the proper specification.

Forget the rest of the bull****. Forget the horror stories....they are designed to transfer your hard earned money to someone else.

Do it right, the first time, and forget it.

It's a non-issue.

Adamant1971

How many times do we have read this pissing match fellas. Everyone has their opinion and there is always more than one way to skin a cat.

Just sayin.

kmascotto

Here is a link to the info: At the bottom of each page there is a star icon that indicated whether the application is an "Interference Engine Application". All you need to do is find the applicable application in the chart.

http://www.gates.com/~/media/Files/G...%204312020.pdf

PorKen

Early A/C bracket.

Early front and rear power steering/alternator brackets.

Late starter bracket.

Timing belt 'guide' pulley(s) bracket.

Prototype tensioner bracket (not much changed).

Etc.

hacker-pschorr

On page 105 the V6 interference engine in the Acura is a belt driven and the non-interference 4-banger has a chain. That's for 2011-2013 model year.

Doing a quick search for all engines listed with a timing belt, every Acrua / Honda, Audi, Chevy Aveo and even the Daewoo 2.2L are all interference.

The non-interfearnce belt engines were the 2.4 from Chrysler the 1.6 Ford and Geo Metro 3-cylinder.

That's as far as I got.