My 6 Rib belt is SLIPPING!

[chuckerants]

In my midst of the dyno runs when we trying for 200 HP, my hotside supercharger's boost would read 10 PSI, 9.5 PSI, 9 PSI the 8.5 PSI with the 110mm pulley.

After we tightened the FIXED pulley assembly, the boost would read 9.5, 9, 8.5 etc.

We never could get the boost back upto 10 PSI after the initial run, but it would still fluctuate around 8~8.5 PSI.

We verified that the car was not pulling timing using a realtime OBD2 reader.

After all that, we still managed to get 202 HP and quit for the day.

The next day Tom had an idea why the belt was slipping.

First, we looked at the 6 rib belt I had on my blower. BTW, I have had a FFS crank pulley for the last 1000 miles or so, but have always had a BRP nose pulley.

The belt's crevices were shiny as if the pulley was slipping and polishing the belt.

This led to Tom and I comparing the two nose pulleys under a magification device at a machine shop. Tom took some pics of the two pulleys and the differences are very telling.

Now me being a layperson and not an engineer, it was obvious when we laid a 6 rib belt on top of both pulleys. The contact points for the belt using the BRP pulley had huge gaps (we could see the light shining through). Whereas the FFS pulley had sharp points of light just visible at the peaks of the belt.

The bottom line though was when we dynoed the car again using a FFS nose and crank pulley and a new Gates belt of the same length - consistant 8.5 PSI run after run after run.

Conclusion: I knew after seeing belt dust under my hood before Tom and I did anything a couple of months ago that I had belt slip. But, now I realize that the problem just may be the (BRP) pulleys themelves. I would not be surprised if all BRP hotside kits (even with the auto tensioner) slips like mine.

Don't take my word for it. Please check your belt to see if yours has the same shininess. I know that Tom's belt did not shine like mine and his belt has many more miles than mine. My belt only had a couple of hundred miles on it.

[Tom @ Fast Forward]

If the pulley is properly cut, the belt, when laid on the pulley, should have daylight (about 0.020") like this.

http://www.FastForwardSuperchargers.com/PulleyWear/belt-pulley.jpg

It appears that the stock hotside pulley is made to the correct taper (40*) but the tool has too large of a radius and, when plunged to the correct depth, makes the wall to wall distance too wide and the peaks too narrow. This allows the valleys of the belt to ride on the peaks and not get traction on the side walls where 95% of the contact is supposed to take place. When the belt is under tension, it pulls the ribs even tighter into the side walls of the pulley. If the belt rides on the tips of the pulley, it allows for slippage no matter how tight you get it and that allows for wear. Pulleys that are not anodized also increase the possibility for wear but, if properly cut, will go a long time before that occurs.

Here is an FFS supercharger pulley along side of a hotside pulley. Granted, the FFS pulley is new and the hotside pulley has a couple thousand miles on it but, the FFS pulley on my 99 has over 15,000 miles and the black anodize which is only a couple tenths of a thousandth deep is still all there.

http://www.FastForwardSuperchargers.com/PulleyWear/Pulley1.jpg

[chuckerants]

This shows the 6 rib belt that was on my car for less than 1000 miles.

http://www.chuckfullobeans.com/images/misc/belt_glaze.jpg

[Kyp J]

Tom

Would the original BRP Coldsides you shipped have the good or bad SC pulleys. I tried looking at mine with the original (most used belt) and it looked OK to me, but I can't see it that well where it is currently sitting (under the manifold on my workbench with a lot of other stuff in the way).

The belt shows a little glaze in the valleys of the belt but no glaze on the sides of the V's. The pulley grooves don't look stepped like your picture on the right.

An off topic question. Do you know the torque spec. for the motor mount bolts to the block? I can't find it in any of my sources or searching the Mnet. All the lists I can find don't include it.

My engine is in the car, ($3127 of machine shop work) trans and PPF bolted in, trouble getting to some of the spots but am going back in with more tools. Conflicts with cooling changes, 2 things in the same spot. Going to try more heater hose modifying.

[chuckerants]

Kyp,

I've seen Tom's coldside belt and maybe my photo doesnt show it very well, but his belt that has been on th car for many many miles has no glazing that I can see.

As for Tom's illustration, if you take the belt and pulley off the car, then place the belt on top of the pulley, you'll see what the illustartion shows.

[chuckerants]

BTW, that glazing on my belt isn't just on that part of the belt. It is all the way around the belt.

[99mx5]

Kyp, If both your pulleys are anodized, then you have Toms design. All of Toms pulleys are black.

Off Topic, Do you have any pics of the cooling changes?

[Tom @ Fast Forward]

All of the SC pulleys were supplied by me. Crank pulleys were supplied by BRP unless they were 105mm. Mine were anodized black and, I believe, theirs were always unanodized.

When I get back to my computer I can look up those torque specs for you. Am currently on a mission to drop off a spacer at the shop to be drilled and tapped for an e-cool upgrade. :)

[Kyp J]

Speaking of E-cool, I couldn't find the thread where you were discussing the "one off" machine shop charges to drill and tap the manifold. My shop charged me $90 and it looks really good. Just like the pics.

I will have a couple of pics of the cooling changes later. I am tied up trying to put the engine back together. Fighting with PS and AC brackets now.

[Tom @ Fast Forward]

I tried to find that thread for Kingdon today and couldn't find it either. No longer matters but if anybody finds it, make a note here. I'm sure there was a search word I needed but I just couldn't find it.

[Scuba Steve]

Here is another view on this thread. I decided to compare the new FFS SC pulley to the BRP pulley. In the attached picture you can clearly see how sharp the peaks are on the BRP pulley as compared to the FFS pulley.

It also appears as if the Gap between the peaks is wider on the BRP pulley. You will notice the BRP pulley is about .073 wider overall that the FFS pulley. This width measurement is where the belt resides, not the width of the entire pulley.