AO

I agree.

6.0-928S

Thanks for the kind words Mike. That's the way I looked at it as well. The unit I'm using was designed to be on a leveraged bracket because of its high tension. I felt it would have to be a firm unit to replace the Porsche design so I removed the bracket & used it straight up. It was from a 2007 Volvo V8 serp belt but it has such high tension without the bracket (but with oil damping) that I chose this unit. I watched the Tech Training video on this new tensioner to get the design theory first. It had all the attributes I felt were necessary. (As with your excellent post on your cylinder & block work showed you), Had I known that some people could merely LOOK at the picture I posted & determine that it was the wrong design damper I could have saved a lot of time researching the damper & just asked them.
Regards, Hammer

6.0-928S

Thanks dude. I realize what's at stake. It's not the first time I've done engine design mods. For my son's first car he wanted a 455 Buick Stage II. (I don't know why, I've never had a Buick) And he wanted it to crank ungodly rpm's. 455 Buicks don't do that! They don't use solid lifters because they can't spin high. Nobody made (at that time) strong rods for them either. He saved his money & asked me to build him a screamer. The motors rpm was limited due to the oil pump being part of the front cover & also driving the distributor gear. If you cranked up the oil pressure it would wipe out the gear in a day or two. So I plugged the oil galleys in the cover, mounted an external oil pump made for me by Petersen Fluid systems, rerouted the oil feed galleys, & fed the motor externally from both ends at the same time. I bought Pontiac custom rods, remachined them to fit the Buick, put in solid lifters & bingo! 7700 rpm! The Buick guys said it wouldn't work. Sometimes you have to do your research, & have confidence in your abilities. Take the step. That's how progress happens.
This tensioner mod may fail (I don't think so) but even if it did it would never stop me from trying mods in the future.
Regards, Hammer

atb

Hammer wrote

Amen to that.

JEC_31

Welcome to teh intrawerb. We're all armchair quarterbacks, backseat drivers, and devil's advocates!

Personally, I think this is the kind of research that could result in big changes - like one of these solutions (Hammer's DIY Volvo unit or Porken's aftermarket unit) becomes a very common upgrade in the community.

Mike Simard

Hammer, the Buick 455 is indeed a hard motor to get to live over 5500 rpm, I've blown up a few and have done similar oil mods, those darn huge mains. Let me know if you want a mini thread hijack about past Buick v8s!
BTW, after tackling the tensioner, do you feel like delving into dampers?

mark kibort

has our tensioner ever failed in a 928. one thing ive learned so far, is that the oil is not really needed. scot and I have our systems running dry, or with a little oil. both of ours were leaking and when it stopped, the mess went away and things are good. ive also done belt tension tests at cold and hot conditions and see no real difference. (measureable anyway)

mk

heinrich

Hammer I'd try it, looks good and robust to me.

mark kibort

this design looks VERY dangerous. the entire point of the 928 tensioner,is to provide positive pressure on the timing belt tensioner roller. if that is allowed to collaps under quick acceleration, based on this spring design, then the tension would be reduced and the belt could jump teath.

the current 928 design is a positive pressure design, not a shockabsorber design. the only thing the 928 little spring does is if there is slack in the belt over the designed spec, the spring pushes out the contact area to break the sensor wire connect to give a warning. there is no shock absorber in our design. this is a REAL risky design, especially not knowing the forces acting on the belt under dynamic conditions.

all this talk about oil, finally got us all to understand that the oil was just a heat transfer mechanism, and is really not even needed . ive been racing with out oil in the cylinder, that as was mentioned, barely covers the washers anyway, for over 5 years. as i mentioned, there is no difference in tension on my engine hot or cold. ( at least measureable anyway)

I hope it works, but dont be surprised on the first set of 6000rpm revs, if you skip some teeth. there are no gurantees, like there is with the stock set up, you are using a spring design from an entirely differnt car and design.

just my opinion. be careful!!

MK

heinrich

Mark, with no oil,m the washers will eat the interior of the tensioner housing. I have seen pressure in tensioners with no oil, fluctuate widely. Not so in oiled tensioners. I do believe oiled tensioners are less prone to be a factor in belt failure. Good point about the stocker being positive pressure, but Porken's Audi unit is also (I think) sprung?

6.0-928S

I didn't forget you on the damper buy Mike. I just haven't had the time to take the old one off & send it to ATI. My old engine is still in the car. I'm going to do it. I know the importance of a high quality damper, especially on a stroker. It won't be much longer, keep the faith Brutha!
Thanks, Hammer

Shark Attack

Don't you make me bring back that old avatar of yours I got friends ya know.... I can do it... Randy V likes money

mark kibort

I took scots apart and there is no wear. Are you under the impression that the washers are actually an active spring? i dont think they move much at all, aside from some thermal expansion that i have yet to see a difference in a hot and cold motor. And, for 5 years, my tension has been set at spec and has never wondered. As bill said, testing the expansion of the washers is tough to test, but i gave it a shot. I warmed the car up and quickly tested tension , and there was no difference. (measureable). so, either there was heat transfer without oil, or need for the heat transfer is not enough to worry about. Introducing a spring set up where as before, there was none is VERY risky. We dont know the force dynamics of the belt under accel and decel. this could be a HUGE formula for disaster. Our tensinoers are positive pressure,(like a threaded shaft with very little, if any movement) This is the reason scots tensioner, just taken apart for the 2nd time, shows no scoring of the internal bore. there is some oil inside, but its residue. if that was a concern, you could just lube it up with some grease.

this could be a disaster. again, you are alowing some compliance on the belt, when it was not desinged to incorporate ANY. the current stock tensioner is very good, and the weak link is in the tensioner warning set up and the owner/operator who checks and sets tension.


MK

6.0-928S

I assume then that from my picture you have calculated the spring pressure on my tensioner? How is it that you KNOW how much tension this unit provides? Please tell me your clairvoyant methods. Have you spent your money to cross section a perfectly good, brand new unit to research the design like I did? How have you determined that I'm "allowing some compliance" on the belt, pray tell!
The world waits!
Hammer

mark kibort

Im only looking out for you and anyone that hasnt completely thought this through.

what i do know, is the porsche design has little or no compliance.(almost like a threaded steel shaft)
what i do know is a spring has a spring rate.
what i do know is that a spring mass system will have a natural frequency. when that frequency is matched by a vibration or resonance of the belt at some rpm. (keep in mind, the belt and engine are tuning forks and at somepoint, that frequency or harmonic will be achhieved over a speed range) so, that will exacerbate and create forces that i dont think you have taken into consideration in your design.

what i dont know, is the spring rate. I know and everyone will know, there is some compliance. what i dont know, is how much. why dont you tell us what that value is. also tell us what the forces of the belt on the tensioner are at different acceleration rates. the faster you accelerate the engine, the greater the forces are on the tensioner. do you have a value or set of values to insure that they will not compress the spring and create a chance of belt slipage?

my clarvoyance is limited to seeing a certain spring with a certain diameter of wire with a certain amount of coils. this tells me that if a full turn of our tensioner is 1.5mm and thats the differnce of a belt slipping and not slipping (actually .5 of a turn goes from loose setting, to correct setting) so, lets call it .75mm. if your spring can be compressed with some force to .75mm, i would be concerned.

I think you will agree that my questions and concerns are valid. I'm not speaking from any other perspective than that of a general knowlege of how the tensioner works and some varibles that you are introducing.

Mk