Boost pressure is boost pressure. It doesn't matter where it's coming from whether it be S/C or T/C. What's gonna hurt an engine is how good the tune is, much torque you make, how hard the torque comes on, and how high you rev the engine.
Basically that ^^
Boost is a measurement of pressure in a given area. It has nothing to do with the amount of actual air. You could have 25 psi of boost with an inefficient intercooler setup with the same amount of usable air as 10 psi of boost properly intercooled. That 25 psi is going to be hot air (which expands, causing a rise in pressure), and you're going to make no power with it, since you'd have to retard the timing to prevent detonation.
What really matters is the CFM or lb/min or kg/s (depending on the compressor map) that the supercharger can flow. These are available for most centrifugal superchargers, and turbos. Boost pressure is used to calculate the estimated CFM's required to make a given amount of power, temperature considerations are given as well, along with drivetrain loss, engine inefficiencies, and supercharger efficiency, in an attempt to determine what supercharger will be required. When it's actually put into a setup, one may find that they have too much boost, or not enough, due to piping sizes, and things such as cams that allow more airflow into the engine, and actual temperatures in the charge piping.
An example: Say I've done all the calculations (feel free to shoot me a PM if you want to know more) and I want to make 280 hp at the wheels. After my calculations, I've determined that running about 13.8 psi should yield me the power I want based on the estimated efficiency of my intercooler setup. The basic engine airflow rate is about 260 CFM (also calculated), times boost pressure of 1.94 (1.94 atmospheres...1 atmosphere already exists, so we are adding .94 atmospheres, or .94 X 14.7 psi to get 13.8 psi) which equals 504 CFM. In this case, the compressor map I will be using is in kg/s (metric unit), and the conversion is kg/s = CFM/1731.8. This yields 0.29 kg/s as my desired airflow rate at 1.94 psi. Now you look at the
compressor map of the C30-94 made by rotrex. Draw a line from 1.94 psi across the page, then draw a line up from 0.29 kg/s up the page. This intersection point will show you both the efficiency of the SC in that area (the higher, the better), and the rpms required to push that amount of air. In this case, the goal is about 85,000 rpms. Now you'd set up a pulley ratio to get the SC to turn at that RPM. (I run a 7400 rpm redline, so for every 1 turn of the crankshaft pulley, you need the SC pulley to turn 1.21 times given that the internal gear ratio is 9.49:1.) If you draw a line from that point to the origin, this SC is PERFECT for the application- it is always in the best efficiency area, and leaves room for future improvement.
The reason for s/c psi being low is because it will make power the majority of the time compared to turbo.
Totally untrue. We are talking mainly about centrifugals in this thread, as thats what F2 will be using. Centrifugals do the same thing as a turbo- except they don't spool up at 3-3.5k rpms like a turbo. You're going to make more power, and faster with a turbo. One advantage of a centrifugal supercharger is that on a front wheel drive car, you actually have a chance to get some traction, as the boost doesn't hit all at once like it does with a turbo. Centrifugal SC's are perfect for high RPM action, such as drag racing. They allow you to get traction in the lower gears, then provide constant top end boost like a turbo does...except they wont blow the wheels off when you hit boost. Not to mention that a SC isn't going to hit full boost until redline, versus 3-3500 for a turbo. It comes on linearly, so remember that running 10 psi max means most of the time you're going to be around half that unless you run the car to redline every time you shift. This also means that your max boost pressure is going to have less effect on engine wear- if you don't rev the piss out of it every time you drive it. A turbo is going to spool and boost every time you accelerate, the Centrifugal SC's are only going to make a few psi until 4k+ rpms.
If we were talking roots or lyhsolm twin screw blowers, yes, they would make power more consistently than a turbo on a street driven car. The problem is that #1 No one makes a twin screw small enough, I've looked. #2 The torque that a roots blower makes down low is totally useless on a front wheel drive car. Ex: Cobalt SS/SC. Second gear is the only useful gear. First gets destroyed on accident, and 3rd, 4th, and 5th are too tall for the roots blower to power through.
Tuning has a lot to do with the prevention of blowing up an engine, but it starts with the intercooling. The cooler the air, the less chance you have of detonation, and the more power you can make. Use of an intercooler, and potentially water/meth injection can make a LOT of usable power on lower boost levels.
Sorry for the long-winded explanation, but I'm sure some of you were curious to learn a little bit more. Like I said PM me if you want any more info/have questions. (And yes, those are numbers based off my own calculations for that power level with relevance to my own car. This is non-intercooled, but with water/meth injection 65% efficient)
