Yea. That plus the sc is a constant drag on the motor.
Taken from Eaton's FAQ section:
http://www.eaton.in/Eaton/ProductsS...motiveAftermarket/Superchargers/FAQ/index.htm
Q: What is this black plastic object on the side of my supercharger? What is a bypass valve?
A: That object is the bypass valve vacuum actuator. This unit has a vacuum port that connects to the supercharger inlet between the rotors and throttle body. This actuator opens and closes a bypass valve for the supercharger. This valve is open when throttle loads are low and closed when throttle loads are high.
With the bypass valve open there is no pressure being created across the supercharger. This allows the supercharger to have an almost negligible parasitic loss in this condition. With the bypass valve closed, all airflow is routed through the supercharger and boost is created in the intake manifold. In some newer applications this actuator is also controlled by a solenoid.
Q: …but my turbocharger gives me “free energy” because it uses otherwise wasted exhaust energy! A: This is a common misconception amongst people today. A turbocharger does indeed use the exhaust gas to be powered but this energy comes at a cost. The engine must provide extra pumping work during the exhaust stroke to provide sufficient energy for the turbocharger.
This pumping work is not present in normally aspirated or supercharged engines and causes a parasitic loss on the system comparable to that of a belt driven supercharger.
Also, take note of the diagram, suitably labeled, "Power (required to drive supercharger)" here:
http://www.capa.com.au/eaton_mp62_4th.htm
This diagram assumes the bypass valve is closed, and the supercharger is creating above-atmospheric pressure ("boost"). According to Eaton's testing reflected in the graph, it takes roughly 35hp to spin an MP62 @ 16000rpm (blower speed) - Note that most users do not exceed 16000rpm on either K20's or K24's, though there are "crazies" among us
(For reference, a stock diameter K20Z3 pulley (5.75"), and a 3.15" blower pulley, with a rev limit of 8600, will produce roughly a 15500rpm rotor speed on an MP62 - roughly my configuration, at present) - Speed calculator ->
http://www.willbelayforfood.com/rsx/rsxmainsite/BlowerCalcPage/blowerspeed.htm -OR- (crank pulley diameter / blower pulley diameter) x drive ratio (which is 1:1 for the MP62) x engine rpm = blower rpm
So far I drove about 1000 miles with the kraftwerks kit and I got about 15 mpg but that was due to a lot of testing and tuning. I took a 300 mile trip and got about 24 mpg just average driving with the occasional wot on I-95.
