[andymoraitis]

Hello All,

My name is Andy and I'm in the process of picking up a blown 94 Cobra with a Vortech V-1. My experience is in turbo DSM's and I had a question about supercharging that I hoped you might answer

I know that since turbos are driven by spent exhaust gases, that once the turbo spools, boost remains constant based on the settings for the EBC or MBC, however I'm wondering why a supercharger only makes maximum boost at maximum RPM. As an example, I noticed when driving this Cobra that it made 11 psi, but only at 5700 RPM.

I'm thinking that since the blower is driven from the crank it's relying on engine revoltions to make spool and won't make full boost unless the revs are high, but I just wanted to be sure. Please accept my apologies for my newbish question. I know tons about turbos, but very little about blowers.

Thanks in advance for your help,

Andy

[mdvaldosta]

You've got the concept down pretty well, a supercharger for the most part is identical to a turbocharger other than how it's driven.

A turbocharger is just much more efficient (but requires much more work, cost, and space to install) than a supercharger. A typical turbo system may have the capability to reach 30psi of boost, but is regulated down to a modest boost level via a wastegate.

A supercharger doesn't use a wastegate, maximum boost is controlled by varying the size of the blower pully. It's true that you'll see max boost at redline only with a centrifugal blower.

The faster the blower spins, the more boost is made. Really the same thing goes for a turbocharger, but it make so much more boost that it's not noticable like that once you start wastegating the excess.

[andymoraitis]

Thanks for your help MD. That makes perfect sense to me. I've driven blower cars before, but never paid attention to how the boost reacted with respect to RPM.

I suppose one could put a 20psi pulley on a blower and use an MBC coupled to a wastegate to regulate boost down to 10 psi, but I prefer the pulley setup since it's a no brainer.

Thanks again for your fast reply,

Andy