Quote:
Originally posted by RASchemel
how do you size a supercharger to an engine? I notice that the whipple 1600 ax displaces 1.6ltr, which roughly half the size of our 3.3 ltr motor. Would you want to use a supercharger of the same displacement?
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Supercharger manufacturers make 3d plots of supercharger output. The whipple twin screw supercharger is a positive displacement blower meaning that for every turn of the input shaft a set amount of air is intermeshed between the rotors and forced through the blower. In the 1600 ax the set amount of air is 1.6 liters. The input shaft of the blower is spun by a belt connected to the crank pulley. The size of the pulley on the input shaft of the blower is sized as a ratio of the size of the crank pulley to spin the supercharger at the speed you want in order to force the correct ammount of air through. The size of the supercharger you need is a function of how fast you will be spinning it, how much air you want to force through it (how much horsepower you want), and the size of the engine which as a ratio to the amount of air you are forcing through the supercharger determines how much boost you are running (pressure in the intake). You're actually after a quantity of air not an amount of boost but as you force a quantity of air unfortunately the pressure goes up and makes life hard on us. If you look at the magnuson products website you can find their 3d plot of supercharger performance for each model. Their plots are fairly simple to read because they sell a lot of supercharger head units to people who make their own systems. From the plot you can see there is an input shaft speed and boost area where the supercharger is most efficient. You want to size your supercharger to produce the amount of power you want when run in that efficient range.
I don't think whipple even provides plots of their supercharger performance because they don't really sell bare head units to the common installer. You have to go directly to lysolm who has the intellectual property rights and does the manufacturing. Whipple superchargers are actually lysholm superchargers. Because they could care less about you buying a supercharger their plots are not very easy for you to read. The ideas are generally the same though and the information is excellent. Because twin screw superchargers are much more efficient at higher boost levels the output you will get from a twin screw compared to a similarly sized roots will be much higher. You'll won't get any nice little cfm graphs to go plug into your turbo calculator though. The lysholm engineers don't know what a cfm is and could care less about selling their products to someone who doesn't know how to do the math themselves. They aren't much into psi either. You'll see #'s like 1 2 3 on their plots which are ratios of atmospheric pressure.