Lower Belt Roller with PK Tensioner
03-07-2012, 10:18 AM
#1
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Lower Belt Roller with PK Tensioner
What's the current thinking on keeping the lower belt roller in place with a PK tensioner?
Because of the size of the tensioner roller and its' proximity to the crank gear, there's only a very short section of belt between them. Is there still value in having the roller at that spot?
Because of the size of the tensioner roller and its' proximity to the crank gear, there's only a very short section of belt between them. Is there still value in having the roller at that spot?
03-07-2012, 10:20 AM
#2
It isn't going to matter either way, the belt never touches it. I generally don't remove them if the roller is still in good shape.
03-07-2012, 10:35 AM
#3
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Had I read this thread (below) before doing mine, I would have probably removed it. Next belt, if it's still turning okay, I may leave it on.
https://rennlist.com/forums/928-foru...-thoughts.html
https://rennlist.com/forums/928-foru...-thoughts.html
03-07-2012, 12:42 PM
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I removed mine.. No need for them the PkTensioner controls the belt much better than the factory one did.. Even with the factory tensioner that roller should not make contact with the belt..
03-07-2012, 01:30 PM
#6
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mines off
03-07-2012, 01:49 PM
#7
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I take them off for the weight, but there's no problem leaving them on, if it makes you feel better. 
Timing belts can try and squirm out of the gear teeth at very high rpms, but I don't think the 928 rollers were put there for this reason. I have not found another 'V' engine that uses them. Subaru boxer engines with manual transmissions have a guide to keep the belt on at high rpms.
I have literally done thousands of WOT runs to the rev limiter, testing my S300s chips, hundreds of those being No-Lift-Shifts (dual 6700/4800 rev limits), and a couple over 7000 by accident, w/o issue. The PKT keeps more belt wrapped on the crank gear vs. stock, so I feel fine leaving the roller(s) off.
The factory originally used a plastic guide, then one roller in '83, two rollers S4-GT, and back to one with the GTS. The second roller makes no sense?
Timing belts can try and squirm out of the gear teeth at very high rpms, but I don't think the 928 rollers were put there for this reason. I have not found another 'V' engine that uses them. Subaru boxer engines with manual transmissions have a guide to keep the belt on at high rpms.
I have literally done thousands of WOT runs to the rev limiter, testing my S300s chips, hundreds of those being No-Lift-Shifts (dual 6700/4800 rev limits), and a couple over 7000 by accident, w/o issue. The PKT keeps more belt wrapped on the crank gear vs. stock, so I feel fine leaving the roller(s) off.
The factory originally used a plastic guide, then one roller in '83, two rollers S4-GT, and back to one with the GTS. The second roller makes no sense?
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03-07-2012, 02:00 PM
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If it makes any difference when I was working with Mitsubishi Eclipse's and Eagle Talons there weren't rollers like this. And people would put down 400-500 hp on stock motors w/o having timing belt issues. And some of these guys were pushing 7-9k rpms.
03-07-2012, 04:05 PM
#12
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Stringing a new belt is easier with that roller in place... it keeps the belt from trying to jump teeth on the crank sprocket, when trying to persuade a new belt onto the pass-side sprocket.
Or maybe I'm doing it all backwards
Or maybe I'm doing it all backwards
