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Silent1 · Apr 24th, 2008, 12:01 AM

Quote: Originally Posted by sam_a156 (original)

Keen to hear comments on this too. I also saw a tangible drop in boost.

My -17% Alta v2.0 is already on its way. Going to swap my current JCW & +3% crank setup to oem crank and -17%.

Personally I would think that going for bigger reduction might not allow to raise the rev limiter so much as -15% due to overspinning the s/c. Suppose 7400/7500 should still be ok though(?)

Sam

Revving the engine to 7500 RPM with a 17% pulley would spin the supercharger to ~19313RPM that's 3313 RPM over the maximum safe limit of an M45, the thermal inefficiences you're going to encounter at that RPM would almost certainly negate any benefit from spinning it that fast.

At the very least you're going to encounter a drastically shortened service life for the supercharger as well as the fact if it does let go spinning that fast i wouldn't like to guess what else it will take out.

Apr 24th, 2008, 12:01 AM	#8
Silent1 Supercharger Noiseaholic Join Date: Nov 2006 Location: East Anglia Local Time: 06:48 PM Posts: 180 Offline	Quote: Originally Posted by sam_a156 (original) Keen to hear comments on this too. I also saw a tangible drop in boost. My -17% Alta v2.0 is already on its way. Going to swap my current JCW & +3% crank setup to oem crank and -17%. Personally I would think that going for bigger reduction might not allow to raise the rev limiter so much as -15% due to overspinning the s/c. Suppose 7400/7500 should still be ok though(?) Sam Revving the engine to 7500 RPM with a 17% pulley would spin the supercharger to ~19313RPM that's 3313 RPM over the maximum safe limit of an M45, the thermal inefficiences you're going to encounter at that RPM would almost certainly negate any benefit from spinning it that fast. At the very least you're going to encounter a drastically shortened service life for the supercharger as well as the fact if it does let go spinning that fast i wouldn't like to guess what else it will take out.