Forget the word "psi"... it simply doesn't matter as a reference. There are sooooo many variables that affect pressure that making comparisons between two engines is almost impossible. A fair comparison is blower speed... and ultimately, CFM. There is a point in any blower where the lobes are moving so fast that they can no longer ingest air on the intake side to pump through the blower and ultimately into the engine. This point effectively destroys volumetric efficiency and generates super-heated intake air. This "point" is a blower speed... lets use 15000 rpm as an example. This means that if I wanted to keep my maximum blower speed at 14900 rpm, and I have an engine redline of 8500 rpm, I would try and create an overdrive ratio of 1.75... which would actually create a blower redline of 14875 rpm. Whatever the "psi" is at this blower speed, with my displacement, my exhaust, my intake, etc. is... what it is. Incidentally, I hope that it is only 11 psi so that I do not have to change MAP sensors... the GM 3-BAR is really ugly !!!
At lower boost levels, both the LHT intercooler and water injection will create lower intake charge temperatures, and thus allow one to increase boost slightly without incurring detonation. Unfortunately, since high-boost applications are already reaching the performance limits of the blower itself, there is no headroom for gain. Blowers have efficiency ranges just like turbochargers do... when you keep them within those confines, you will make the most power possible.
Consider BoostedEX's example again: His bone stock JDM B16A (1595cc and 10.2:1 compression) @ 10 psi made 207 wheel HP. I installed a CRV shortblock with Crower rods and JE pistons (1973cc and 10.5:1 compression), and using the exact same pulleys as before, made 252 wheel HP @ 7.5 psi !!! So, by increasing displacement and increasing compression, we made large gains without changing the blower speed.
How is this you say...
Simple. The additional displacement offers greater breathing power within the engine... it will use more air per revolution than a B16A will. Since the blower moves a fixed amount of air based on rpm, it would make sense that less pressure would build within the intake manifold. Also, the blower is most efficient at lower blower speeds because the amount of time that the blower lobes are open to ingest air at the inlet is LONGER... which translates into greater fill per revolution. As the blower speed goes up, the fill rate goes down. When the blower lobes reach redline, the fill rate is dismally low and the air within the intake manifold begins to recirculate... which makes REALLY HOT AIR !!! Obviously, there are additional scientific forces which also affect the airflow (intake pressure pushing back toward the blower to limit incoming air is just one), but I am simply offering an example or two to illustrate the TRUTH about what we can and cannot accomplish with the Gen 3 M62 blower.
