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Pas Belt Turning Inside Out / Coming Off?

Chris Wilson
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Chris Wilson Proficient

Chris Wilson

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RB26 engine with a sequential box turning only to an 8500 RPM limiter. I am 99% sure the PAS pump, pulley and bracket are correct and compatible, and they are all OE, the crank damper is new and stock. On the road I have no issues, but on track I get the belt either turning inside out or coming off broken. I have heard this can be an issue, especially with sequential dog boxes and un-damped clutches, which is my set up. I use the car for track work. I have made a pulley to run on the outside of the none tension side of the PAS belt, as it seems a long run, to hopefully dampen any oscillations. It seemed to ripple when revving and coming off the throttle. Pulleys seem perfectly in line. Has anyone else had issues? I haven't yet tried it on track to test my theory. Thanks.

R31Nismoid Grand Master

R31Nismoid

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^ I was going to say the same thing.

OEM belts by are large are the best. I know there was some issues with Daikin (or something similar) "replacement" bands that were cheaper than Nissan OEM, thing was though they just shredded far too easily. Happened to me :)

Back to OEM and it was fine there after. Not exactly the same situation, more so evidence that it shouldn't be the belt...

  • 3 weeks later...
Chris Wilson Proficient

Chris Wilson

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^ I was going to say the same thing.

OEM belts by are large are the best. I know there was some issues with Daikin (or something similar) "replacement" bands that were cheaper than Nissan OEM, thing was though they just shredded far too easily. Happened to me :thumbsup:

Back to OEM and it was fine there after. Not exactly the same situation, more so evidence that it shouldn't be the belt...

I double checked pulley alignment, even borrowing a Gates laser pulley alignment tool. All was spot on. I got a reply from a UK forum suggesting the hard shifting of the sequential dog box may have caused belt oscillation on the long un-driven run. This made sense, for example Toyota Supras in manual form have a damper (shock absorber) on the auxiliary belt tensioner that's not fitted on automatics. I made a simple bracket to mount a cam belt idler pulley for some engine or other (4-AGE Toyota I think) to run on the back of the PAS belt. This has cured it completely, and it ran maybe 80 laps of a fairly long UK race circuit at race type speeds, with race type gear shifting. Thought I'd share in case someone comes upon this in a search. Two UK drag racers using RB26 engines have had this same issue, similarly cured. Thanks.

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