The turbo-superchargers of the USAAF radial engines and the P-38’s Allison V-12 are still superchargers, the drive and control operation just differ. They were all remotely located from the engines as they required complicated air ducting and lots of space.
Disabling the complexity of the turbo and waste-gates of the turbo aircraft would be the easiest given their physical separation. The mechanical superchargers would have required modification of the engines to simplify the supercharger operation but it was done in the interests of reliability and maintenance economy.The Aerofly P-38 has a manifold pressure of about 36 inches at full throttle at take off from sea level. If the aviation authorities approve that or a very similar maximum manifold pressure for civilian use in a de-rated engine with the turbo disabled, which they very well might do given the war time permitted boost being about twenty inches higher, the full throttle height would be at sea level. There would be no need to throttle back in the initial climb until reaching a height where holding the maximum manifold pressure corresponded with the throttles being fully opened.
Without operating turbos there would be no critical altitude, the height where the engine’s automatic boost control has the waste gate fully opened.
I was kidding about the discrepancy between superchargers and turbosuperchargers.😅
But some ww2 turbocharged engines had a first stage engine driven supercharger, and a second stage turbo supercharger. My point was that the second stage could be disabled, leaving the first stage supercharger in operation. That first stage doesn’t necessarily need to have its critical altitude at sea level.
In any case the Allison V-1710 -111 and -113, found on the P-38L models, have a second stage turbo supercharger according to this table: Allison Piston Engine Specifications. However I can’t find the critical altitude of the first stage, which may actually be at sea level.
