To be fair and impartial here is my take:
I have turbocharged a lot of different engines in my short 34 years.
I have found that PSI does not equal horsepower.
To prove this follow along with me.
I had a 5.0L 305 Chevrolet engine with 8.7:1 cr, 1.94 valved 58cc Dart SR torquer heads with nothing other than a gasket matching done, Summit Vortec truck shorty tube headers, factory 5.7L roller cam, Victor Jr drilled for 36 lb injectors, a 90* adaptor for a 70mm Mustang TB, a modified HEI and a Megasquirt computer and finally a Modified GN turbo.
The little Chevy engine made 391 horsepower 385 ft lbs and 24 PSI. (flywheel)
I took the Turbo, injectors, computer, throttle body and adapter and put them on my gasket matched GT40P headed 8.8:1 306 Ford with a factory GT cam, Flowtech shortys dimpled for the P heads, and a Victor Jr and guess what I came up with?
Henry made 401 horsepower and 377 ft lbs and did it at 19 PSI. (flywheel)
WHY?
As an air pump the Ford engine offered less restriction to the incoming charge building less reversion and in turn less pressure. When I cranked the boost up to the same 24 PSI we had passed the thermal efficiency of the 306. while we made 428 horsepower and 393 ft lbs they were peaks and the rest of the numbers suffered greatly.
PSI and boost pressure sound great but they need to be used in relative terms.
example:
Racer A - "My car flows X cfm through the system and I run XX PSI and make XXX horsepower with that boost."
Racer X - "My car also flows X cfm, but I only run Y psi to get to XXX horsepower, I think your intercooler sucks or something! Let's compare them to see the difference."
Now that that is said, I would like to know the target peak boost that can be made, and suggestions on how to get there, for the following combo:
-Stock million mile 1990 SC bottom end with fresh rings and bearings.
-Heads and lower intake gasket matched, Heads flange matched to 1998 Mustang shortys.
-1990 Blower case to be ported (need good reference as everyone their opinions!)
-Water injection pre blower switched on above 9 psi
-Larger TB (need reccomendations)
-Megasquirt-N-EDIS computer, 8x8 table, no mass air to get in the way.
-2.5" Mandrel bent exhaust, NO CATS, total exhaust length 52" per side with Dr. Gas x pipe and side pipes with Dynomax 2.5" race Bullets.
-Mandrel bent aluminized IC piping, Intercooling has cool air ducting as well as an Icewater sleeve on IC to manifold pipe near IC.
-50-125 shot Nitrous oxide shot in to the IC to manifold pipe for drag racing and/or smacking ricer bitches around.
I don't need a lot to complete phase 1 of this build, as I have most parts but I do like to know everything I need to know when going into these unexplored (for me) territories.
Oh yeah remember this ain't no stock heavy bodied MN12, this is a 1550 lb Datsun SPL1600 Roadster!
Click on pic for close up