Had alot of belt slipping problems on dyno , found 1" longer 12 rib belts for 25$ each online. Thinking of adding a extra idler on power side of belt which will force belt to wrap around pulley more BUT concerned about belt oscillating while under power. Have never seen a idler on drive side of any blower, wondering IF anyones done anything like this? Not much room to add one on idler side. Any opinions?

Or ripping 1/2 " bolt out of bracket when its under full power?

i added a xtra pulley near the compressor on a pair of m4 engines i did a few years ago.it really helped but i also went with a stronger [green] belt.these engines should have had cog pulley,s&belts.EDIT IN.you need to use a grade 8 bolt and it will not break or move around.

Were you able to find a green 12 rib, there is very little out there or was it a 8 rib? I saw green stripe 72" 12 ribs but would be 7" longer than my stock one, i know CNC's m4s use a 72"

I converted my M3 to COG for this very reason. Another thought might be to run a larger crank pulley and larger blower pulley.

The larger crank pulley was a idea i had too at one point but the chunk of aluminum to build one is 400$ and machining it on a manual lathe and mill would be quite the undertaking so i havent done it, aside from the fact the belts are only available in 66", 72" etc once you go bigger than the procharger sizes. I welded strong backs on my head bracket a few years ago and made beefier spacers which virtually stopped the flex they have. Recently the 1/2 inch shorter belt that goes with my smaller 3.70 pulley got installed on a 3.85 pulley and just that tiny bit less wrap made it almost impossible to make boost past 5500 rpms which made me realize how touchy the wrap aspect is. So I plan on using a 1" longer belt with a extra idler, just could not find anything, anywhere where a belt driving a blower wraps around anything vs pulling in a straight line from crank to blower, tensioner and idlers always seem to be on back side taking up slack.

https://www.youtube.com/watch?t=12&v=XJ1I_NtxVK0 Is this the set up that you built??

here is a pic of the set up i found that has an extra pulley near the compressor

http://www.performanceboats.com/atta...4&d=1396895897

I don't see why you couldn't do just that.. Serps wrap around all kinds of funny ways on motors these days.