turbo for power , superchargers are belt driven , anyone with a/c on a 4cyl knows how much it slows them down , superchargers' take power to make power,turbos' dont....I built a 2.0 s/c car at 18 psi , made less power than a 1.8 we did at 14psi, but dam 18 psi without a turbo to quiet it down,PLUG YOUR EARS....

 

I suppose I should have put in a clause about parasitic drive loss. The drive loss depends on the type of supercharger, and there is flow involved in that also, so it's not a perfect comparison.
Anyway, you're trying to say that turbos don't use any power? So a turbo doesn't present any restriction to the exhaust system, and there isn't any pressure drop across it?? So it doesn't affect exhaust scavenging and cylinder filling because there isn't any difference in pressure from one side of the turbo to the other?
So it goes against the laws of physics, I get it..

 

no comparsion as exhaust has to get out anyway... yes it has more loss than open header , but thats why we use tubular man. not "logs" anymore, .... blow on a pinwheel, the reach up and spin it with your finger , which requires more effort?

 

Blow on the pinwheel and try to jog at the same time.

Exhaust has to get out anyway, and you're restricting it's flow by putting a turbo in the way. Now you have positive pressure acting against the exhaust gases coming from the engine, which lowers the engine's volumetric efficiency. There is power loss, you can't argue that. Part of that is offset by the increased power generated by the turbo, but the bottom line is you're totally wrong saying that turbos are free power. Period.

 

i cant jog , hell i cant even type fast....

ok your correct, its not free power , but the again what in life is truly free?? my point was only that at the same boost level on the same engine , with similar tune based on v/e,and afr, a turbo will almost always out perform a s/c ,

 

The question was compression vs. 6 PSI of boost and whether that is safe on a stock engine.

This all comes back around to the original question about whether it can handle whatever amount of boost. The power that the engine makes is dependent on cylinder pressure, which depends on the intake air pressure for a given engine setup. Whether you use some of that power output to the wheels or to drive a supercharger doesn't matter, the tuning for the engine still has to be the same for a certain boost pressure. Tuning for 6 PSI supercharged is the same timing and same amount of fuel, and same cylinder pressure, except that less power makes it to the tires.

Does it really matter if you make more power to the wheels at a certain boost pressure with a turbo if your engine blows up at that pressure?

Sure, you can make a lot more power with a turbo, but it's not going to be much more at 6 PSI.

 

I can't make up my mind, so I have both...

 

ok but who is happy with 6psi for long? but points are correct

 

If you knew how much it costs to build a M3 engine for safe tuning at more than low boost, you'd be happy with low boost for a while I believe..

 

Ok, turbos are generally more efficient than superchargers, and generally will have much lower IAT's.

A good efficiency for a turbo is about 78%, and a good efficiency for a roots type supercharger is about 65%. That means, a turbo running in it's 78% efficiency range will transform 22% of it's energy into heat. The supercharger on the other hand will transform 35% of it's energy into heat at peak efficiency. Lower heat = higher power.

Also, if you go with forged pistons, they will more than likely be able to withstand a higher egt than your stock cast pistons will. Your limitation is not your compression, it is your fuel and your tune.

I would suggest learning how to read compressor maps, and do some research on which turbo/supercharger will flow the right amount of air for your application. Then make the decision for yourself.