Quote:
Originally Posted by Gromic
Altitude issue with spits also (1a + 100oct).
At around Angels 11, I get sporadic engine ticking and 50rpm fluctuations (magneto drop?) which quiets down if rpm is reduced to 2600. Going higher to within 15k I have to drop boost to 2lbs. max or the engine feels like it's about to shake out of the aircraft. ASI shows 140 IAS at that altitude and continually drops to around 110 at 22k.
I'm enjoying the low altitude speed increase of the 100oct spit. Pushed one to 305 miles on the deck with 12lbs full boost / 2600 rpm and rads at 35%. Just watch your temps. They climb much faster (as it should).
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I reached 300 mph at deck with SPitfire MK 1a 100 Octan at +12 lbs 2850 RPMs, radiator 1/4 open so it is not bad but still other planes are too slow example Spitfire MK II is slowier 290 mph at +12 lbs 2850 RPMs and 260 mph at +9lbs ( should be 290 mph at +9 lbs), Hurricane MK1 at 6 1/4 boost reached only 240 mph/390 kph - should be 260 mph/418 kph.
I found that still Merlin engines had RMPs kick at different alts depend of planes and there is need to lower throttle from full postion and drop mainfoild pressure to got smoth engine runinig which is strange to me - it cause lose power. Engine with single stage supercharger should lose manfoild pressure byself with altitude.
Also Merlin III from BOB era should have allowed climb settings ( 1/2 hour limit) at 2850 RPMs below 20 000 ft and 3000 RPMS above 20 000 ft.
Still there is too much engine power lose above 15 000 ft and above 20 000ft climb rate is lees then 1000 ft/min - nearly minimal climb rate at minimum (near stall ) speed so RL service celling is not possible to reach with steady climb.