J7W1 Shinden (2 Viewers)

Sounds like a reasonable estimate: That's around the ballpark that liquid cooled 1945 aircraft designs with similar power levels were hitting, and the pusher configuration means it's a much more "bullet-shaped" aircraft than the typical 1945 radial. There could be some unpleasant "boat tail drag", but I think the contouring of the spinner and taper just before would keep this to a minimum, especially with the cooling system ejecting additional hot, high-pressure air into this region

Of course, I doubt it would be achieving these values in a real-world scenario, but that's more because of the poor state of Japanese fuel and industry by 1945, and the fact that every engineering project tends to have at least one "ambushed by reality" moment: P-51B tests had problems with the merlin's piping and the cooling system piping corroding one another, and the Mustang was arguably one of the least troubled development histories of a WWII aircraft.

I assume that the performance figures in this thread are those the Japanese hoped to attain with the J7W Shinden and not data from actual flight trials?

Because AFAIK the two J7W prototypes that were completed did not do any full MIL power (1730 hp SL) speed tests?

I reverse engineered what flat plate drag area you would need to attain to get a SL speed of 593 km/h with 1730 hp and got a flat plate drag area of around 0.365 sqr m. This is a flat plate drag area that is only about 95% of the Mustang's and, given that they have roughly the same wing area, you can compare Cdo as well, and the Shinden is consequently (on paper at least) an extremely aerodynamic design.

However, note that while the Shinden is often attributed a wing area of about 20.5 sqr m, it looks like to me (based on the drawing in Burindo's book page 33) that this is more in the order of 21.95 sqr m counting the "wing area" inside the fuselage as per modern convention.

But it's of course entirely possible that a pusher like the Shinden will have a very low drag area because of no slipstream effect over the fuselage and the way the cooling air exits, which may help to reduce the wake behind the fuselage, in combination with the negative pressure gradient the pusher will give on the rear part of the fuselage since it's essentially sucking the air off the rear fuselage backwards,

But I'm not entirely convinced the Japanese were not being a bit optimistic here and that the impressive speed numbers are more a product of wishful thinking than anything else. But maybe someone has data on this? As in actual Cdo/flat plate drag data for the Shinden? Or maybe data on other similar pushers like the Curtiss XP-55 Ascender for example?