[jrglenni]

With the new superchargers like the Eforce and Techco coming out, I see a lot of claims about their efficiency and how they make more power with lower boost. I'm having a bit of trouble understanding this (and I'm guessing it's because I'm misunderstanding something) since to me it seems that no matter what power adder you are using, the same amount of boost should make the same amount of power. Shouldn't, say 5lbs of boost from a KB, be the same as 5lbs of boost from any other charger? Isn't the boost the measurement of additional pressure inside the combustion chamber?

I can see how one system might be more efficient than others in terms of requiring less power to make power, but not the drastic differences that these systems seem to poses. What am I missing?

[stlwagon]

It all depends on the design of the impellers/rotors in the supercharger. Some are more efficient at compressing air at the same rpm than others.

[jrglenni]

So what your saying is that one SC may be able to produce a spike of boost at a certain RPM while a more efficient one may be able to maintain that level throughout the engine's RPM range?

Am I wrong in my assumption that, ignoring all other factors like RPM's etc., a boost level means the same thing no matter whatSC it's coming from?

[jrglenni]

Where exactly is supercharger boost measured, is it intake manifold pressure? Is it at the start of the intake, right after the SC or is it closer to the pistons?

If it's at the start, I can see how a more efficient design would lead to the air flowing more freely and in turn, producing more HP as the engine will breathe better. If that's the case, then an efficient SC running at say 5 lbs. of boost might push as much air into the combustion chamber as a less efficient SC running 7 lbs. of boost, correct?

Not only that, but the parasitic loss of the SC wouldn't be as high since it would work less hard producing less boost, therefor more power would be able to go to the wheels.

Am I thinking along the right lines here?

[mell0]

somewhat along the right lines. the boost is measured at the intake manifold right after the throttle body. i dont have much time now but i can go into detail and help you out later on.

[jrglenni]

I would appreciate that. An SC kit is next on my list, but I'm having one hell of a time trying to decide what to get. I'd like to keep costs down as much as possible, so the idea of going with a non intercooled Vortec or Paxton and adding the intercooler/swapping pulleys later on is appealing. However, I also want to make sure that whatever I get is not going to be strugling to produce big HP on down the road.

[mell0]

Originally Posted by jrglenni

I would appreciate that. An SC kit is next on my list, but I'm having one hell of a time trying to decide what to get. I'd like to keep costs down as much as possible, so the idea of going with a non intercooled Vortec or Paxton and adding the intercooler/swapping pulleys later on is appealing. However, I also want to make sure that whatever I get is not going to be strugling to produce big HP on down the road.

the efficiency can be thought of as simply how much power can be added at the same psi. the kenne bell "screws" (the two screws that spin inside of the supercharger compressing the air) are designed a lot better than say the two "screws" (actually lobes) in a cobra's stock eaton supercharger. therefore with the same size pulley a kenne bell will create more pressure than a eaton (not necessarily spot on considering there are several eaton designs but you get the point).

also the gearing in the supercharger has some say in this too. much like changing out the rear end gears in your stang. my procharger for example has a 4.1:1 ratio. so for every time the pulley on my procharger spins the impeller blade spins 4.1 times. so basically my supercharger is always spinning 4.1 times faster than my engine. in other types (paxton, vortech etc) might have different ratios so they might not create the same pressure as soon or as easily as my unit (once again not necessarily correct i'm just trying to make it so you can understand it).

the amount of air that is being moved also matters too. say two superchargers are both making 10 psi of pressure but one is making it out of a 2x2 square and the other out of a 4x4 square. the one making it out of the 4x4 square is obviously moving more air so that would allow it to make more power.

all in all i would go ahead and do the intercooler now. that way you wouldnt have to pretty much install the entire kit twice. and with most superchargers these days, more power is just a pulley swap away and if that somehow doesn't create enough power for you then exhaust work, head work, and beefing up your internals would surley quench that thirst.

hope that helps!

[jrglenni]

Ok, that does make more sense. Thanks for the help!

[95gts silver/bl]

also look at the heat it takes to make 10 psi of boost.they new designs make less heat to make boost so thats a big plus because of all the heat soak they get after running for any length of time.

[BlueLou]

This is a link to a write up on Kenne Bell's site.
http://www.kennebell.net/techinfo/ge...efficiency.pdf

Three types of efficiency related to superchargers it covers are volumetric, temperature and adiabatic (aka. overall) efficiency.

As you said, it takes power to make power (that's the overall efficiency). Temperature efficiency, Roots' discharged 10 psi is going to be hotter than 10 psi from a centrifugal.

This is another link from Kenne Bell's site:
http://www.kennebell.net/techinfo/ge...romcatalog.pdf