15% pulley+ 2/3 % crank pulley..+ alta-nator

[Il Generale]

Hello , I'm running a 19% supercharger reduction pulley , but now I'm looking for this setting : 15% supercharger reduction pulley + 2/3% oversized crank pulley and the 5% alta-nator pulley..I'm looking for this configuration because my engine red-line is set at 7650rpm..it's not stock..
I like the 3% cran pulley...to reach a 18% reductionpulley ratio
what do you think about it?

Can I use the original belt size.. .?

[k-huevo]

I fail to see the logic in swapping pulley percentages, crankshaft and supercharger after the fact, in response to the raised red line. If you’re concerned about overshooting the efficiency of the supercharger at that rpm, it would be more productive to return to a stock size SC pulley, and avoid larger crank shaft pulleys. It would surely be less expensive to go larger on the SC pulley than make all the changes needed to improve flow in order to take advantage of overdriving the SC to that extent.

Depending upon the manufacturer of the crankshaft pulley, a 15% SC pulley reduction combined with a 3% increase in crankshaft pulley diameter may not equal the same SC rpm for a given crankshaft rotation as a theoretical 18% reduction in SC pulley diameter. One percent of theoretical SC pulley diameter difference will have little or no impact on SC efficiency.

The alternator has a voltage regulator to keep charge in check so I don’t see the need for a compensating pulley for that component.

[Il Generale]

Quote: Originally Posted by k-huevo (original)

I fail to see the logic in swapping pulley percentages, crankshaft and supercharger after the fact, in response to the raised red line. If you’re concerned about overshooting the efficiency of the supercharger at that rpm, it would be more productive to return to a stock size SC pulley, and avoid larger crank shaft pulleys. It would surely be less expensive to go larger on the SC pulley than make all the changes needed to improve flow in order to take advantage of overdriving the SC to that extent.

Depending upon the manufacturer of the crankshaft pulley, a 15% SC pulley reduction combined with a 3% increase in crankshaft pulley diameter may not equal the same SC rpm for a given crankshaft rotation as a theoretical 18% reduction in SC pulley diameter. One percent of theoretical SC pulley diameter difference will have little or no impact on SC efficiency.

The alternator has a voltage regulator to keep charge in check so I don’t see the need for a compensating pulley for that component.

Thank you for reply..
I want to use a 15% on the supercherger to prevent the belt problems..

[Fisher]

Quote: Originally Posted by Il Generale (original)

Thank you for reply..
I want to use a 15% on the supercherger to prevent the belt problems..

Change the belt every 10.000km and everything will be OK.

[Richard Crofts]

Might be worth PM to ThinkMINI as they did run a 3% crank on Bert (thier test car) along with his normal 17% pulley for about a week or 2 ... ask them what belt they used for that and it might give you an indication of wether you can use the stock one on a 15% with +3%.

I also know that Bhozar used to run the stock JCW pulley (11%ish) with a 3% crank... he might also be able to tell you what belt he used and so give you an idea if stock will work for you?

I just change my belt every year (10-15k miles) and it usually has not quite developed any major slip at that point.... but I'm only on a 15% pulley

[MINI-Morgan]

Dont forget an alternator pulley too with such high crank pullies. Personally id recommended staying away from big crank pullies but its upto you if want to try