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I think that the Obama administration may have to regulate separate bathrooms for the two of us...
tea all over the keyboard 8>)
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
The removal of the rollers has always been a customer defined option when fitting a PKT. When asked I will in future reply that the seized bearings should be replaced and the assembly be left in place for additional peace of mind.
HAI as a side note did the water pump sit on 2 pins to locate it to the block? if one or both were removed then the pump could migrate upwards thus increasing the amount that must be taken up
I find it interesting that everyone is searching for ideas on what could possibly be undersize (or wrong) to cause this particular Portensioner system to be extended so far, yet not a single person has considered that the home made tensioner bracket could be the source of the dimensional issues.....
While I'm just a rookie at this whole Portensioner thing, I'm guessing that the hole for the fulcrum (just as one example) doesn't have to be very far off to greatly affect the extention on the tensioner.
Seems like that would be a more likely place to look, than for an anomaly in the mass produced pieces.....
yet no one has considered that the home made tensioner bracket
Greg there is nothing "home made" about a PKT - I get it that you are happy to bash the PKT but sometimes it is better to not make derogatory remarks like that.
Because your fantastic engines are not put together by the factory I guess that makes them "home made".
I certainly know that not to be the case but likewise the PKT is not built by Porsche but machined and put together by a competent person in a competent machine shop just like your parts.
I am sure all the component parts of the system will eventually be analysed and a conclusion made.
My aftermarket cam gears were made by a machine shop specializing in making cam gears - I guess that makes them Home Made to you as well. However I am happy that they also be checked for mistakes - who knows they could be undersized.
I am also interested in the checking of the PKT.
As always you have very important statements to make but please be civil my friend.
Greg there is nothing "home made" about a PKT - I get it that you are happy to bash the PKT but sometimes it is better to not make derogatory remarks like that.
Because your fantastic engines are not put together by the factory I guess that makes them "home made".
I certainly know that not to be the case but likewise the PKT is not built by Porsche but machined and put together by a competent person in a competent machine shop just like your parts.
I am sure all the component parts of the system will eventually be analysed and a conclusion made.
My aftermarket cam gears were made by a machine shop specializing in making cam gears - I guess that makes them Home Made to you as well. However I am happy that they also be checked for mistakes - who knows they could be undersized.
I am also interested in the checking of the PKT.
As always you have very important statements to make but please be civil my friend.
Roger....try to relax.
While everyone is looking at remote anomalies thst might cause the problem, no one had mentioned the possibility that the actual bracket was a pretty important part of the equation and that any variance of that bracket would radically change the geometry!
There's another thread going that is discussing the facts that people are getting radically different tensioner extentions when using all new parts....on similar engines.
What is the common denominator?
Seriously, when 2mm of difference (7mm to 9mm) in travel is the difference between "perfect" and "junk"....you people need to figure this out.....quickly!
Two millimeters isn't very damn much when dealing with a rubber belt!!!!!
I'm sorry that "homemade" ruffled your feathers. I can easily see that the bracket has some milling on it and spends some time at some sort of a machine shop. However...forgive me for saying this.....it does look like it was made in a high school metal shop.....and until it is made from billet and CNC machined....I'd actually expect there to be some variance.
Enough of me trying to talk logic to the people that drank the Koolaid.....you people could rationalize Hillary being a good president!
It just so happens that I'm doing the machine work and getting ready to assemble a GT engine, where the owner wants a Portensioner that he provided.
I've got a few different Portensioner brackets, made at different times, a whole bunch of used parts, enough new parts to do 10 belt jobs, slightly used belts, very used belts, new belts.
I also run each engine, on a test stand, before shipping or putting it into the chassis....it's super simple to run an engine with the cover off.
I tell you what...I'll spend my own valuable time and "play" with all the different pieces and run the engine when it seems logical to do so and see what the difference is, between hot, cold, running, not running, new belt, broken in belt, etc.
Understand I'm not going to be stupid and assume that the lower roller is "vestigial" and run the engine without it....I'm not intentionally going to try to turn this thing into junk. I'm not going to run the engine when the tensioner is "over extended" and thus can't put enough pressure to keep the belt on a four cylinder Audi tight enough to run.
Who knows....maybe all of this will turn me into another emotional Fanboy!
In the meantime, if you Fanboys quit making stuff up and telling crazy lies about things you have no idea about (lower rollers, gear wear from belt tension, failures of the stock tensioner, water pump failures), I'll completely step out of this thread and we can allow the OP to figure out why his "premium" belt replacement resulted in a ruined engine.
The first person who tells a lie, makes something up, tries to make an opinion fact.....
I'm sorry that "homemade" ruffled your feathers. I can easily see that the bracket has some milling on it and spends some time at some sort of a machine shop. However...forgive me for saying this.....it does look like it was made in a high school metal shop.....and until it is made from billet and CNC machined....I'd actually expect there to be some variance.
Actually, that bracket looks pretty close to what a car factory would've made in the 80's, other than plating. You can tell the "home made" aftermarket part immediately, if it's CNC machined from a "billet". Car factories very rarely do that. Instead they press, mold, or cast most of the time. So I'd say it's exactly the opposite of what you say in terms of what's factory appearing and what's not.
In terms of the substance of accuracy of fabricated parts, I think the most important determinant is if the piece is machined before or after the other fabrication. Part that can keep its form that is machined after fabrication is going to be very precise, in my opinion, regardless of the fabrication method.
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Actually, that bracket looks pretty close to what a car factory would've made in the 80's, other than plating. You can tell the "home made" aftermarket part immediately, if it's CNC machined from a "billet". Car factories very rarely do that. Instead they press, mold, or cast most of the time. So I'd say it's exactly the opposite of what you say in terms of what's factory appearing and what's not.
In terms of the substance of accuracy of fabricated parts, I think the most important determinant is if the piece is machined before or after the other fabrication. Part that can keep its form that is machined after fabrication is going to be very precise, in my opinion, regardless of the fabrication method.
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That didn't last long....
Forgive me....I just haven't noticed any cobbled up, welded together, steel brackets on any new all aluminum Audis, Mercedes, Porsches, or even Chevys.
The first person who tells a lie, makes something up, tries to make an opinion fact.....
I'm back in....correcting.
How about correcting whether the racing belt is made of Kevlar or not, whether the racing belt fits with the stock lower rollers or not, whether the PKT with lower bolts burns the rollers, etc. You've got your work cut out for you with corrections.
Have you seen "billet" cnc machined brackets in them?
Of course not....those cars are mass produced and they use cast aluminum pieces for economy.
Not a welded steel bracket bolted securely to the front of an aluminum block. With the size of that bracket and the difference in expansion rates of the block versus the steek, I'm amazed they can be retained on the block for a year, much less 80,000 miles.
While I'm just a rookie at this whole Portensioner thing
Exactly. Why do you feel this thread requires you to keep advertising your ignorance of the product?
Or, for that matter, ignorance of how the stock tensioning system works in operation?
It is not just about some static tension readings you bandy about.
Originally Posted by GregBBRD
While everyone is looking at remote anomalies thst might cause the problem, no one had mentioned the possibility that the actual bracket was a pretty important part of the equation and that any variance of that bracket would radically change the geometry!
Seriously, when 2mm of difference (7mm to 9mm) in travel is the difference between "perfect" and "junk"....you people need to figure this out.....quickly!
The bracket pieces are laser cut. The pieces are pickled, assembled, then TIG and MIG welded together. All drilling follows holes pre-cut by laser.
This 7-9 thing that you latched on to does not exist. Stop creating myths. The range is 2mm to 9mm.
No one else has had a problem with this range before with many more miles and abuse.
This one installation experienced an as-yet-unknown anomaly but you are gleeful in your attempts to apply non-information to the entire group of installations.
You desperately try to show how knowledgeable you are, using one detail at a time - provided by others, for 10 pages, then you forget and move on to the next.
Not a welded steel bracket bolted securely to the front of an aluminum block. With the size of that bracket and the difference in expansion rates of the block versus the steek, I'm amazed they can be retained on the block for a year, much less 80,000 miles.
I did those computations for some of the brackets that critical for the turbo car. By my understanding, as long as the steel component is the one that elongates, as long as it's within its limit, it will last. Steel can do a lot of cycles, think of millions. What would've been theoretically problematic in our application either the aluminum elongating in cycles or the steel elongating outside the limits. Now, my computations were based on high school physics and reading engineering textbooks, so who know whether they ended up correct. John did the real ones. What comforts me is that the number of heat cycles of the engine block is low compared to the number of elongation cycles that an aluminum connecting rod sees...
The number of cycles needed to weaken the two materials below (from Wikipedia, posting from children's museum):
How about correcting whether the racing belt is made of Kevlar or not, whether the racing belt fits with the stock lower rollers or not, whether the PKT with lower bolts burns the rollers, etc. You've got your work cut out for you with corrections.
Heh, the guy that contracted the belt to be made by Gates (Roger) told me they were made with Kevlar.....and I've read several different conflicting descriptions of what they are made from....
Don't think this is something that I need to correct.
Look, I get that you are as giddy as a school girl about this system and think it's the best thing since sliced bread.....rhat's cool with me.
I understand that the original design has its own limitations and I'm sure that a properly engineered hydraulic damper/tensioner would work much better....I have no argument with that.
I just don't feel that a random Audi piece, made for a shorter lighter belt, plucked off of NAPA's shelf, in a completely different application, is automatically the correct solution to keep this long belt with completely different camshaft arrangement properly tensioned. I don't feel that a steel bracket "stuck" on the front of an aluminum engine is a long term solution. I think that arbitrarily deciding that the lower rollers are "vestigial" borders on stupidity. And, as an engine builder (something you would not understand), trying to accurately set the cam timing with this system is a virtual guessing game.
I understand you love the system and can find no faults with it, support it to the point of making random crap up.
Seems like I should be able to have a contrary point of view.....especially given that I've installed 1000's of stock tensioners, without one single failure. None.
Just because you drank the Koolaid, that doesn't mean it is a good idea to jump back in line for another cup, while ignoring the dying people around you....
I did those computations for some of the brackets that critical for the turbo car. By my understanding, as long as the steel component is the one that elongates, as long as it's within its limit, it will last. Steel can do a lot of cycles, think of millions. What would've been theoretically problematic in our application either the aluminum elongating in cycles or the steel elongating outside the limits. Now, my computations were based on high school physics and reading engineering textbooks, so who know whether they ended up correct. John did the real ones. What comforts me is that the number of heat cycles of the engine block is low compared to the number of elongation cycles that an aluminum connecting rod sees...
The number of cycles needed to weaken the two materials below (from Wikipedia, posting from children's museum):
Again....you reach for the Internet, while I reach for practical knowledge. I've yet to see a Portensioner bracket removed from a 928 engine that hasn't been moving around enough to leave movement marks on both the bracket and the block.
Every single one!
How many automotive engineers would blow that fact off and just ignore is as being "fine"?
While you search on the Internet for that answer....let me clue you in....
05-28-2016, 11:26 AM
George Layton March 2014
