ATI clutch drive

[SDMAN]

Im curious to see if there is anyone on the board that has used the ATI clutch drive(8mm cog...45 or 48 tooth) on their centrifugal. Looking for feedback. If not, I guess I will order one and see how they work.

[Blown353]

???

I'm not even sure what it is. Care to elaborate?

[SDMAN]

Almost without exception, centrifugal users I have spoken with that use a serpentine drive, all complain about belt slip. So for my setup, I chose to go with an 8mm cog drive.

While Im no expert on any of this, as I understand it, manual trans cars with a centrifugal, using a cog drive, over time will tear the teeth out of the belt from shifting at the upper RPM limits.

These very quick and violent RPM changes in the belt drive (maybe 2:1 crank to blower plus the step up trans) puts a lot of stress into the drive system. Dont know if its as big a problem with automatics given the fluid coupling (converter).

The ATI blower pulley has a one way clutch in it that allows the blower to over run the crank when necessary to remove these shock loads from the drive system, and saves the teeth in the belt. At least thats what its supposed to do. But it aint cheap, and before I give it a try I thought I'd see if someone else had anything positive or negative to say about it. Its a fairly new part.

[Blown353]

Gotcha. I had never seen it advertised before so I did not know what it was.

A 1-way would be a good way to alleviate stress on the supercharger during rapid engine RPM changes... however I wonder how well and long a 1-way bearing will live with that much HP being transmitted through it being subjected to abuse every shift.

Being that it's new and costly and especially that it's from ATI I'd wait a while and let others do some longevity and durability testing for you. LOL!

I'm a happy serpentine user myself. Additional idler pulley + GM spring tensioner courtesy of SDCE = over 15K miles now on the original 8-rib belt with no slipping, glazing, or other problems. Stick transmission too.

[sc68z28]

They are calling it a sprag, "ATI performance" the trany part guy's.

More info here, w/vidio. http://www.atiperformanceproducts.co...lley/index.htm

It's a very interesting deal

I use a 12 rib, minor slippage probs @ 17+ boost, 4.0" pully
No probs when I use my 4.25" pully, 16#'s at 7K.

---Bill.

[SDMAN]

Good info. I'm definitely going to use one. My motor wont be complete until the end of the year.

[Blown353]

Very nifty indeed.

Now that I see it's the balancer "ATI" guys making it and not the Procharger "ATI" guys, I'd be much more willing to give it a try even though it's brand new. I have much more faith in the balancer guys getting something right the first time than Procharger. LOL!

[Texas Hotrod]

That's interesting. What is the price on the sprag pulley? How much is a new belt? Which one won't dent the 'ol pocket book as bad?

Stripping teeth from the belt sounds more like a tension/skip issue, than a pulley issue to me (but I could be wrong). I noticed that the return side of the belt went loose on that last revving, and that wasn't even high rpm/high boost. A boosted run on that belt would have produced even more slack (making it skip over the teeth???).
The inner shaft only made 3 revolutions before it stopped when they cut the engine. Surely not enough force to generate belt damage.

Has anyone seen the inside of one of these 'chargers? A gear driven impeller making boost builds a lot of resistance, it won't freewheel with 17psi+ behind it. Bill said that his slips under boost, I believe that. Blown353's belt looks fine with that many miles on it, so his doesn't slip when coming off the gas or it would show glazing.

Is this special pulley heavy??? It does spin 2Xengine speed. So it's more weight that has to be flung up to speed, taking more torque away from the engine in the process. Just seems fishy to me.

Coming from an oild-school 6-71 user. Proper belt tension and routine expection would more than rule out the use of an expensive (reliability questionable) gadget.
Ever heard of the k.i.s.s. rule? Keep it simple stupid (Im not referring to you, or anyone else here as stupid). I'd just carry an extra belt in the tool kit if it was me.

Though it is a cool looking piece.

[Blown353]

The air flowing through the supercharger, even with the bypass valve open and the flow being non-compressed, keeps a constant load on the impeller and geartrain but during fast transient downward engine RPM changes (i.e. fast shifts & clutch dumps) the belt and supercharger geartrain could certainly be shockloaded as the geartrain "clanks" over from the drive side to the overrun side when the engine RPM decelerates faster than the supercharger would decelerate on its own without a belt. Given the power needed to drive the supercharger at high RPM/boost I'd imagine the supercharger would decelerate VERY quickly on its own, probably at a rate equal to or greater to most engine RPM changes save a clutchless shift on a drag car or someone dumping the clutch.

The overrun ability of the sprag would "cushion" the supercharger a bit from the crankshaft and save some shockloading on the supercharger and the belt during severe engine RPM changes. I'd like to see instrumented test data to see just how necessary it really is. My hunch is that the engine only "out-decelerates" the supercharger during really, really fast shifts & clutch dumps. Still, I'd rather shockload a sprag in a pulley than the geartrain and bearings in my supercharger.



I see this sprag pulley as added insurance, not a necessity. I've done a couple cogged Prochargers recently and haven't had any problems. Previously all I did was serpentine setups (which are my preference) but for the last 2 applications both the owners "had to have the cogs" for carshow appeal and not for performance reasons. Guess they like paying 3X more for belts and also getting no warranty on their headunits for use of the cogged belts. LOL!

With routine inspection, tension adjustment, and maintenance, the cog belts will live a long life. However they're not cheap to replace...