Originally posted by Widewing
When I have a little more time, I'll calculate acceleration for these two, and I'll give the Tempest an extra 5% more prop efficiency when calculating thrust. The lower the speed, the greater the available thrust.
Acceleration in feet per second, per second = Thrust - Drag/Weight/32.2
IIRC, the Tempest has a profile drag coefficient of about .0245, with the P-51D coming in at .0176 (with pylons, .0168 without)
My regards,
Widewing
A quick calculation based upon 80% prop efficiency shows me that acceleration is as follows.
Beginning at 150 mph
Tempest: 8.44 ft/sec/sec
P-51D: 8.69 ft/sec/sec
Tempest at 85% prop efficiency: 9.21 ft/sec/sec
At 300 mph, the rate of acceleration slows to:
Tempest: 2.32 ft/sec/sec
P-51D: 2.93 ft/sec/sec
This makes good sense as the greater profile drag of the Tempest begins to tell more at higher speeds.
This is based upon weights of 11,480 lb for Tempest and 9,611 lb for the P-51D.
Total drag used for the Tempest is 1,350 lb, 845 lb for the P-51D (based upon profile drag coefficients, wing area and dynamic pressure at sea level, meaning that increases in altitude will result in decreased drag).
Horsepower depends on boost.
I used 1,720 hp for the V-1650-7 and 2,180 for the Sabre IIA at 9.0 lb boost. Greater boost means greater power. However, I'm going by standard boost of 67" MAP for the Packard Merlin and 9.0 lb for the Sabre.
By the way, if I add the 2,800 hp P-47M to this, you would see that it runs away from both of the others.
One other factor that bugs me is the P-38J/L. Using the same calculation, it should accelerate faster than the P-51, Tempest or P-47M. Currently in the game, it's about even with the P-51D, which means it accelerates rather slowly despite 1/3 more hp than the Tempest and a total drag only slightly greater than the P-47M. It strikes me as very odd. I have no idea how profile drag is coded into the game, so I can't even begin to guess why this exists. It is what it is and we have adapted to it.
My regards,
Widewing