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My under standing with the 8rib solution, has to do with slip more than stretch.
This is why the LSA has a separate belt track, so they run a larger crank pulley and thererfore larger supercharger pulley.
The Gates belts are quite good with stretch from my memory while at GM Powertrain. The focus where was belt slip, not stretch.
I'll run the 6rib and see how it goes.
Also, I'll be running an auto, so no clutch assist for me.
Yes you could be right, they slip then get tensioned up beyond their limit and stretch perhaps. I would really suggest you speak with both Bullet and BD as they are now selling this upgrade as a standard I believe. What peeved me was that that they knew about the issue and were ready to sell me the 6 rib, then admitted the 8 rib was the solution. I had to still pay the extra as the pulleys were custom made and probably got a refund on the kit from BD - no idea - cant follow his invoicing!
The belts have a nominal tension force bandwidth, as supplied from the belt supplier, so, if you follow their specs, you can't over tension, with the supplied spring tension pulley.Quote:
Originally Posted by PeeBee
I suspect what happens is that there is belt slip, and to compensate, the belts are over tensioned.
You get belt slip if the s/c pulley is too small, as many people over drive them to get more power.
This is bad FEAD design.
Anyway we will see how it goes.
I will not be rushing out to go 8rib. yet....
What pulley are you moving with?
Whats interesting is that the slip is supposedly happening at the s/c, yet that is the driven element, the crank is where the power is transmitted to the belt and the likely location of the slipping I would have thought. Or is the compression rate within the S/C too high a driven load, so the belt slips at the pump? Interesting.
I am going with a 70mm as standard and a 75mm as a back drop. 79 is in the region of 14-15psi and 75 in the region of 10-12psi
Slip happens at the S/C pulley and is a function of "length of contact" which is why the smaller (overdriven) pulleys slip.
This is going to be really interesting as it plays out. From what I have been told, and the photos i have of the particular engine involved, it had a dia 75 6 rib, with close to a 185 deg wrap on the s/c pulley, and those belts were lasting less than 5000klm before they ran out of adjustment as they had stretched, ie were slipping so they were tensioned up. These belts were running on that engine as described for 70000klm. It was so bad the owner carried 4 spare belts with him as he does a fair bit of remote travel in WA. This is to produce a boost of circa 10-12psi, which is relatively tame i would have thought. He has now moved to the dia 65mm pulley, and is waiting for the 8 rib pulleys to arrive , same units as i am waiting for except i am staying with 70 and 75 dia.Attachment 77194
at 14psi this s/c will take some 80hp to drive......
what are they asking for the 8rib setup?
1800 plus whatever bullet charge for the pulley, maybe 250
so 2k for about 4 pulleys, wow, where do I sign........