Hello,

Anyone have any more information on a rule of thumb for belt slippage, particularly with an 8-rib setup (6.66/2.95)?

I was just going through some of the impeller speed calc's again and I am contemplating pullying for ~10% above what I am actually shooting for.

Thoughts?

-Scott.

 

The belt should not slip if it's adequately sized for the amount of power transmitted and installed correctly. IOW, do not add 10% for slippage.

Rich

 

Thanks Rich,

I see your point, but how do you quantify that? Theoretically a ribbed belt should not slip and this is how the rpm formulas are setup. Should we assume XX% efficiency in driving a blower with a ribbed belt?

Belt slip seems to be a legitimate concern with these types of setups. I wonder if anyone has gone from ribbed to cogged at the same ratio with any findings.

Furthermore, I wonder that if I mark the blower pulley and belt with paint would I see the two points offset after driving?....at full throttle?

Thanks,

-Scott.

 

If the belt slips, it's most likely to do so when you let off the gas after running at max boost. This is good, to a point, as it helps prevent surge. If you do as you propose, it is a mistake and you will be driving the blower 10% faster than you intended.

 

I disagree, the belt will slip some with the ATI setup. My suggestion to eliminate most belt slip without blowing your budget is to have the inside ribs sandblasted from both the blower and the crank pulley for better traction. Also, have a machine shop mill 1/16 off each end of the pulley grooves to allow the belt to sit deeper in the pulley's. This has gained 1-2 #'s more boost on many cars at my shop. MY car turns 7k rpm's on a 3.4 pulley, and I think that is a good indication of proof my method works. Also, I would give your blower at least a 5% cushion from the blower max rpm just to be safe. It's an expensive part and the extra risk does not produce much better results. My .02 though.

 

I've got an 8 rib setup from ATI on my D1SC with the smallest pulley combo available for it. Mine doesn't slip at all, but then again I have a SDCE tensioner on it as well.

 

Your tensioner is great. I believe you, but most stock ATI setup's slip some at the crank pulley. I just think the small things can really make a difference!!!