It's adiabatic efficiency, you were close though..

Now you see my crusade here every day.. I just don't come out and say it like that.. lol..

 

I was slightly confused by what you said, then I realized what you were trying to say (and I was over analyzing it of course)..
I wanted to make sure that everyone understood that the engine and turbo efficiencies are separate entities...

Efficiency of the engine from a having a certain compression ratio doesn't have to do with the efficiency of the turbo. The efficiency of the turbo has to do with where it is operating within its efficiency range (and is a characteristic of th turbo itself), which is different at 12PSI, 20PSI, etc.. The compression ratio of the engine affects the volumetric efficiency of the engine.. You can make more power with the same amount of boost on a higher compression engine, etc.

However, the vol eff of the engine does have a big role when calculating a target HP and choosing which turbo to use. The vol eff has a role in how much boost you will need to reach a certain target HP, which then leads to the turbo selection (based on the turbo's eff characteristics). But I digress..

As an afterthought, a turbo can (will) increase the vol eff of an engine. So engine eff doesn't affect the turbo, but the turbo affects the engines' eff...

 

I didnt read the whole thing but I will say this: if youre going to run any type of FI, the first thing you need to do is upgrade your fuel system.

 

6 or 8 PSI often doesn't need any upgrading if there is enough overhead from the factory. Blindly replacing things is expensive and often unnecessary.

 

I have always wondered about the fuel system. So basicly i can just slap on a SuperCharger with 6 psi and thats all? For the M3 BMW of course. And if i want a little more power out of it, ill just add a intercooler and upgrade the fuel system?

Oh yeah, what about the fuel pump?

 

really, if im so ignorant why dont you explain to me why i am wrong?

 

I'd love to hear this explanation also. I think Mike's probably built more fast cars than the rest of the posters in this thread combined.

 

You should be fine, fuel pump, injectors, everything. Again, try to get some info from other M3 owners and see what kind of fuel system headroom you'll have. As far as slapping a supercharger on, not a big deal. Adding an intercooler later though, that's a little different unless you're using a centrifugal unit like Vortec. Most roots or Eaton superchargers replace the stock intake manifold, and there really isn't any way to easily add a intercooler. These are the considerations you have to think about when you're planning out what to do for more power though.

 

Always huh?

Lets say you have a motor that has 9.0:1 compression that can only handle say 10psi of boost before it wants to pop. Now you have a supercharger that runs at 76% adiabatic efficieny (thanks fabrik8) at 10psi. Now say you have a turbo instead of a supercharger. Now at 10psi, this turbo is running at 62% adiabatic efficiency. That means, its putting more restriction on the exhaust/motor causing you to have less efficient of a system and LESS HORSEPOWER.

 

yes allways, maybe when you get your head out of your ass and get into the real world you will understand. any supercharger takes hp to make hp period. yes a turbo is not persay "Free" power. but it takes a hell of alot less to make hp than a supercharger does. ofcourse the size of the turbo/supercharger + boost levels + intercoolers come into play. BUT all things being = A TURBO WILL ALLWAYS MAKE MORE HP!