Hi Karnak
>USA: R2800-77 at 2,800hp?
I believe when including a turbocharged engine in the comparison, it would be necessary to establish the contribution of exhaust thrust that the mechanically-supercharged engines enjoy to a much larger degree.
(I thought WW2 turbochargers would not provide any exhaust thrust at all, but apparently, there were two different types of turbines, and only the equal-pressure turbines could not yield any meaningful thrust. I learned this from a recent article on the turbocharged BMW801 in the German Flugzeug Classic, but haven't been able to figure out which WW2 aricraft had which type of supercharger. The Allisons of the P-38 apparently used equal-pressure turbines as there is one quote from Clarence Kelly expressing regret that he couldn't exploit exhaust thrust in his design.)
Anyway, the R2800-77 quoted above would have to be compared to the Jumo 213A (which is one of the few engines I have seen exhaust thrust data for) based not on the latter's 2140 HP shaft power, but to about 2300 - 2600 HP shaft equivalent power depending on speed. (As a rule of thumb, in a climb the turbo-charged engine compares more favourably than in level level flight.)
I suspect the R-2800 would also add a bit of exhaust thrust on its own, based on the location of the exhausts on the P-47, but that's just a suspicion so far. Any data would be welcome! :-)
Regards,
Henning (HoHun)
