These are the figures I got for time to altitude, compared with the figures the A&AEE got during the war.
Alt...AH IX : 1942IX : HF IX : LF IX : 1944IX
4K.....1.07....1.10..........
................0.50
6K. ...1.38...............1.24...
............1.15
10K....2.42...............2.2
5....2.15.....2.06
18K....4.58...............4.1
8................
20K....5.40....6.00..........
...............4.30
30K....9.52...11.40.....8.05.
...8.40....8.17
My test was carried out by flying at sea level at 180mph then going full throttle and wep then engaging alt-x. The plane climbed at approx 170mph, which I believe is the correct climbing speed for the Spit. Full fuel and ammo were carried, but no drop tank.
Of course, due to the fuel modifier, the plane was a lot lighter in the latter stages of the climb than a real one would have been.
In the above chart the 1944 Spit IX is using 150 octane ful, which I understand was common by 1944.
The A&AEE results can be found at
http://www.fourthfightergroup.com/eagles/spit9.html [This message has been edited by Nashwan (edited 04-30-2000).]