where to buy larger pulley for rotrex c38 sc? (from AA stage 2 kit)

[cpalella]

I will hopefully be installing raceland supersprint euro rep headers, dual 2.25 midsection with x pipe resonators and no cats hooked into uuc rsc36 exhaust this weekend, and next weekend adding the s52 cams I have sitting around. I would like to retune after this to make the most out of the mods and I figure if I am retuning, I might as well add a larger pulley.

Where can I get one?

Car is a 1996 328 with M50 manifold and AA stage 2 supercharger kit. 42 lb injectors. ASC is deleted.

Thanks

[jszy25]

I used the googler

http://www.urdusa.com/p1260518913/Ro...duct_info.html

[cpalella]

I used the googler

http://www.urdusa.com/p1260518913/Ro...duct_info.html

I feel stupid

Thank you.

[jszy25]

Haha no problem. I'm pretty sure that's actually where I bought my 80mm pulley from years ago.

[cpalella]

Haha no problem. I'm pretty sure that's actually where I bought my 80mm pulley from years ago.

Hmmm I have a sneaking suspicion that's the size I have now from the stage 2 kit... Also meant to write SMALLER pulley but I think it was still understood thats what I meant

You don't happen to know how I can calculate increase in boost based on pulley size?

[Butters Stoch]

Hmmm I have a sneaking suspicion that's the size I have now from the stage 2 kit... Also meant to write SMALLER pulley but I think it was still understood thats what I meant

You don't happen to know how I can calculate increase in boost based on pulley size?

IIRC the stage 1 is a 100mm pulley, put a ruler across the pulley and convert to MM.

[black bnr32]

http://forums.bimmerforums.com/forum...?9639-buldogge

this guy made mine, and many others, years ago. custom made to whatever you want, and at off-the-shelf pricing.

[Butters Stoch]

Just sold a 85mm rotrex pulley a couple weeks ago.

IIRC wheel 2 wheel performance makes them. But its been years.

[jszy25]

Hmmm I have a sneaking suspicion that's the size I have now from the stage 2 kit... Also meant to write SMALLER pulley but I think it was still understood thats what I meant

You don't happen to know how I can calculate increase in boost based on pulley size?

You cannot calculate the increase in boost because boost is based off different variables.

When I was deciding on a pulley years ago I used some simple formula to see when the blower would be over spun. I remember the 80mm pulley slightly over spun the blower at redline

[cpalella]

You cannot calculate the increase in boost because boost is based off different variables.

When I was deciding on a pulley years ago I used some simple formula to see when the blower would be over spun. I remember the 80mm pulley slightly over spun the blower at redline

I checked the pulley on the stage 2 kit, 80mm. According to the data sheet, peak input shaft speed is 12,000 rpms and peak input impeller speed is 90,000 rpms. jszy25 you are right, my brain wasn't functioning correctly again. If I am imagining this right, its the relationship between crank pulley size and SC pulley size which will determine the rpms of the SC which will potentially increase or decrease boost. And yea, also right you can't just directly calculate boost, kinda forgot about that too... like with gigantic intercooler, I believe that causes a pressure drop.

Anyway. I can't seem to find a definitive measurement for crank pulley size. Not sure if its different on an M52, but the 2 sizes I came across were 5.25 (133mm) and 5.75 (146mm). So according to this nice pulley calculator with a redline of 7020 (thats what it is on my car atm) and a crank pulley size 146mm the SC pulley is spinning at 12,811 rpms. Just on the nose of its max. With a crank pulley of 133mm its at 1,167 rpms.

So it looks like I can't go any smaller? If anyone sees a lapse in logic please let me know.