By going from a 74mm to a 61mm pulley (for example) you increase the load required by the supercharger from 38kW to 62kW or +60%.
see pic showing the 2 routes....black is stock...green is with "BWK" Belt wrap kit.

You can see if you didnt employ the BWK - you'd have <180deg lap (stock) and lose contact area, but the charger is "requesting more power" (or providing a greater resistance) and so you have a greater propensity to slip
With the BWK discussed here, you increase this to >210deg (give or take) and get better contact area.

Chris - have you (or others) looked into increasing the tension any - say +10 or 15%.
Do we have any tension figures floating around out there?

 

Stuart, I have not given this any serious consideration as the BWK seems to do a fine job of eliminating the slip. But, more to the point, accessories on the SRT6 (alternator, AC compressor, Power Steering pump and even the waterpump) are NOT inexpensive to replace ... and while these accessories have proven to be, for the most part, "bullet-proof" at factory load levels (in terms of loads on their respective bearings) , I hesitate to tempt fate by increasing their loads (particularly when this problem seems solved). But I do like the way you think.

Cheers,
Chris

 

Not that it was really required, but since some have asked about it, I added an optional bracket to put the two 76mm pulleys (smooth pulley and the new grooved one) in double-shear mounting. I also added a new bearing cover for the 90mm pulley on the tensioner.

Cheers,
Chris

IMG_20130422_200613_843.jpg

 

Nice! No, it's...

 

Those pulleys are smoking hot looking. My only obstacle to not getting these today is laziness. Not to mention, mine seem to be getting the job done already. But smoking hot is really luring me in. PM the current price please.

Les

 

Excellent work once again! A nice addition to your setup!

 

belt tension figures - or tensioner specs?

 

Rob. I am going to chrome paint your pulleys. Chris is upstaging you lol.

 

Rob (needswings) is a class-act providing great products and support to the members here that is beyond comparison. I would never seek to upstage him.

... I would recommend silver brake caliper paint DOC : )

 

I've only purchased the alternator pulley from Chris, and am completely happy w/ Rob's kit. Just wanted to mention that it is the American way to pursue building the better mouse trap. Or at least one w/ more bling. Kudos to Rob and Chris, and all here that strive for excellence.

 

credit to all - beautiful things those pulleys, cant wait to get into that side of things.....shame we cant ditch the radiator and show 'em off better...

totally off topic and unrelated.....but someone said a funny thing to me sometime ago....
....A good "rat catcher" always leaves 2 behind....

 

lol. All in fun. No I want chrome.

 

Agreed. I consider Rob a great friend, he has always been long on advice and always entertained even the silliest of questions from me... never too busy to give advice/help.

It also seems you've built quite the good reputation as well. I know dozens of people that are happy with your products, and I plan on being a customer of yours in the future.

And THAT'S what this place is all about. Enthusiasts serving other enthusiasts through innovation and mutual respect for each other.

Can't find that on just any forum.

Keep up the good work, guys.

 

I received the bracket and grooved idler today. Nice!

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NICE! I have an order in to complete mine as well.

 

Looking great! I cannot wait to install mine.

 

I received mine in the mail yesterday. I am waiting for a few other perf parts to come in and these bad boys will be installed.

DSC04610-s_zpsc96eb05e.jpg

 

I have so many pulleys now I forgot which ones to use for the 65mm pulley...lol.... Roadster is getting a needswings PSK....65mm pulley... Now the only difference between the roadster and the coupe is 62mm/fuel pump vs the 65mm pulley...

 

any advance on us poor guys without the additional water pump hole to slip into ?

 

I just wish Chris would offer a water-pump pulley replacement while we're at it. What say you Mr Latemodel21?