Ok I just have a what if question. This supercharger is rated for no more than 680 hp. If my motor was making more than that, would it be trying to suck in more air than the supercharger could put out?

 

I think there are two different sides to this coin. First, if the ratio between the crank pully and the sc pulley won't allow the sc to spin past it's max rated rpm then yes, your engine will try to suck more air then the sc will supply. This will lead to lower then expected boost numbers or maybe even none at all.

Or you could have a pully ratio that will over spin the sc past it's max rated rpm. If the sc doesn't self destruct, it will supply the amount of air the engine wants but it will be at an elevated temprature. A sc can and will spin past it's max rpm, but at a much decreased effieciency. This means more of the energy taken from your engine to drive the sc will be turned into heat, heat leads to detonation, detonation leads to broken parts...

Long story short, overspin it to get more air out of it then it's rated for. If you do this, be ready to deal with a shorter sc life span and the heat it will add to you intake air temps (ie intercooling). People do this all the time, but I wouldn't get too carried away.

 

Airflow roughly = hp. If the thing is only capable of flowing a certain amount of air at a specific rpm that’s all you’re going to get, doesn’t matter how big an engine you put it in front of.

 

Word! And take into account heat and BSFC.

-- Joe

 

heat depends on the blower's adiabatic efficiency in the range that you're using it in, it could be higher or lower depending on the compressor map. Since he doesn't specify a blower or the cfm or lbs/min that he's at...

BSFC depends on a ton of things but probably chamber design more then anything else, since that isn’t going to change much in the range of heads that almost everyone around here runs you can pretty much assume that that is static.