Effect of boost control cutout prior to +12 psi boost modifications

[*Buzzsaw*]

Originally Posted by Viper2000

At the moment, we've got early Spitfires & Hurricanes with combat ratings of +6¼ psi boost at 3000 rpm, and a Spitfire II with a +12 psi combat rating.

Your conclusion the Spit II is modelled with +12 boost is incorrect.

The original tests show just under 290 mph at sea level with 87 octane and 8.8 boost levels. Best alt figures are over 350 mph also at 8.8 boost. Those are actually higher than the results achieved for the game Spit II.

http://www.spitfireperformance.com/p7280speed.gif

The Spit II manual shows max boost using 100 octane is +12.5 at 3000 rpm. See page 13 of the manual:

http://www.zenoswarbirdvideos.com/Im...pit2Manual.pdf

For an actual 100 octane, +12 boost test, we unfortunately don't have one for the Spit II, but the Spit I shows sea level speeds of 314 mph, and best alt of 359 mph at 13,000 ft.

http://www.spitfireperformance.com/s...-rae-12lbs.jpg

+12 boost does not confer a lot of advantages over 10,000 ft.

The Spit II would be slightly slower than the Spit I, speeds at sea level were approx. 310mph.

Note that would mean the Spit would be faster than the 109 at sea level, but would fall behind it over approx. 15,000 ft when 1,4/1.45 ata is used by the 109. (my understanding is the 109 had a limitation of 1 minute at 1.4 ata) Since there are no charts showing speed/climb for the 109E at 1.4/1.45 ata, the developers are going to have to do an approximation as for the Spit II at +12. Of course, the increase in speed is not linearly related to the increase in horsepower, (990 PS for 1.3 ata vs 1100 PS for 1.4) so the 8% gain in horsepower will not result in a 8% gain in speed, as the drag factor multiplies very quickly and there is a lot of Hp required for each additional mph/kph. The 109 would pull away even when using only 1.3 ata at alts over approx. 21,000 ft.

Reports from the actual battle confirm the 109's preferred to stay over 20,000 ft and not engage on the deck. This fit with their escort mission, since the bombers were most often at between 16,000-20,000 ft.

Thanks to Mike Williams for his links from his Spitfire site:

http://www.spitfireperformance.com/spittest.html