Whatever, you want to believe is fine with me. However, your first formula is wrong-- your volume at 1800rpm is always 3.6L at 5400 rpm the engine still is 3.6L at 150,000rpm still 3.6L! Now CFM is also directly related to the more important number--- lbs/Ft3 measuring air-density. That formula looks like this take CFM x .076Lbs/ft3 and poof that is the magic number. I tend to use CFM because it, well, works just as long as you remember to change it over to Lbs/ft3 and then remember that is per minute. Thusly, even a compressor running at .6 PSI operating at X Lbs/ft3 will create less power than a similar unit doing .6PSI with X+2 Lbs/ft3.
Hence my Vortech examples-- at any given Manifold pressure the V-2E has the potential to produce more horsepower than its similar brother the V-2SCI unit. That little 100CFM difference if it is constant across the entire units performance band produces an extra 7.6Lbs/Ft3 of air mass per minute!!! which if you say rough equates to about 30-50hp at any rpm range for any given boost. If that is a constant 100CFM increase. Now it might not be, but it could be. Which would make your analysis totally meaningless if you didn't take that extra air-mass into account for each given boost level.
So here is the general rule of thumb!!!! And it isn't supper accurate, but if you are making 125 HP at flywheel/ by 10.5 = 12.5hp per Lb/min. So if you are at 1800 rpm and you are pulling in an extra 2.2lbs/min of air (which can then be converted over to CFM, LFM, KG/CM3 or ML/CM or whatever you like) you roughly get a 27.5 hp which is pretty damn close to a 40% increase in power if go from 75HP at 1800 rpm to about 102.5HP: So what it is about a 37 percent increase in power? And it only required an addition 2.2lbs/min of air mass to reach the cylinders.
Until you know exactly how much air/mass is reaching the cylinders for a given boost pressure will not tell you anything of importance. Because guess what moving more air at any pressure means the potential for more air-molecules to be found in that specific volume of gas. Damn that air density.
Also on a side not I think you are misunderstanding Pressure Ratio on the Turbo chart. It doesn't measure the ratio of boost produced for a given volume of exhaust- it measures the ratio of compressione from absolute pressure at the inlet of the turbo to the outlet of the turbo. So lets say you have a 1.25:1 Pressure Ratio at 55,000rpm (impeller speed) means that you out pressure is 1.25 times that of the absolute pressure reading of the inlet side. Most turbos never get much more than 3.0 to 3.5 to 1 ratios. But that is pretty damn impressive. That's why staging turbos can get really insane pressures rapidly.
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