by Spec BSC » Thu Sep 17, 2015 2:50 am
Right been doing a bit more research into belt slippage, found an excellent company in the USA, 928 Motorsport, that deal with all types of sc unit including Raptor.
Heres what they say about belt slippage.
Belt slip and drive pulley sizes: Remember that every time you change to a smaller pulley, you loose tractive force on the belt and the ability to pull a load. To make matters worse - you just increased the load - trying to move more air increases the load on the belt, and now you have even less tractive force to do it with because the pulley is smaller.
Solutions for belt slip:
1) go from a 6-rib to an 8-rib pulley system. If 8-rib, go to 10-rib or a cogged pulley system.
2) if using a sprung belt tensioner, replace with static (solid) belt tensioner.
3) if driving the supercharger from a shared serpentine belt that drives the other auxiliaries, change it so the supercharger has its own belt. The supercharger demands 50 to 100 HP to drive it (depending on model, back-pressure, and rpm) and nothing else in that system (the alternator, the power steering pump, etc) do. So the serpentine system is not designed for that load and you will never get the belt tight enough. If you did, you would overload the alternator bearings into an early failure anyway. It is convenient for kit makers to drive off the serpentine belt, but that only works for light supercharger loads up to about 6-8 psi. Put the supercharger on its own crank pulley with its own tensioner.
Also they can coat the pulley to give more traction, ok the belt will wear a bit faster but hey. So I have ordered some belt dressing which is a temporary fix to see if I can get boost to increase, if so will then consider getting my pulley coated whilst considering re-engineering the belt drive system.
The first engine died after eating to much CAT
The second engine died of a broken piston
The third engine is in the car
The fourth engine is in the machine shop
So far: Rotrex Supercharger (16 psi) FMIC,DW300c fuel pump, ID1050 injectors
Producing 431bhp and 350 lb/ft torque on the Rotrex SC not finished yet
Raptor headers, 75mm Milltek exhaust with Quad tips,
Custom made 4032 forged pistons by JE Pistons, forged conrods, Exedy Clutch
K sport 8 pot front, 4 pot rears all on 330mm discs, Hel brake lines
Meister R coil overs, Whiteline 21mm rear ARB, Perrin end links and strengthening brackets
Complete Whiteline kit for the front suspension including steering rack
One off Carbon effect Front grill, Carbon lip spoiler, Exterior De-chromed, LED interior light conversion.
Recaro Leather front seats with all functionality.
Waist spoiler, Smoked rear lights,, LED sill plates, LED sidelights
Prodrive PFF7's 18x8, in Bronze shod with 235/40/18 Goodyears.