Originally Posted by *Buzzsaw*
Salute
I did two hours of tests of the Spit IA and Spit IA 100 octane, less systematic to be sure, but it was online on the ATAG server.
I found all Merlin equipped aircraft had some degree of misfiring and cutting out at certain altitudes, with the effect happening more frequently the higher the aircraft climbed. This became more pronounced when maneuvering accompanied the climb. The effect came on at lower boost levels when the rpm was high, and conversely required higher boost at lower rpms. It was also more likely to happen when you increased the throttle, (boost control) or rpm, (selected finer pitch) rapidly. The effect begins with small stutters, you can see your rpm gauge kick, then as you increase the rpm or boost, the effect escalates into full on misfiring and cutting out. This effect happened without any overheating, and no damage resulted. After doing nearly an hour of testing in a Spit IA 100 octane, with probably 10 minutes worth of misfiring/backfiring, I was able to drop down to below 10,000 ft and use 2800 rpm and +6 1/4 boost to shoot down a 109.
This effect is entirely unhistorical, the carbureted Merlin had no tendency to misfire or backfire at neutral or positive G's, and it was more capable of sustaining high rpms and full throttle at higher altitudes than it was down low. (because the max. boost which could be obtained was lower, especially over critical altitude)
The effect began as low as 8000 ft as far as I could determine, I got misfiring and cutting out of the engine of the Spit IA 100 Oct at 2900 rpm and +6 1/4 boost at that altitude. As mentioned, this occurred even when the engine temperatures were at low levels, 85 degrees C.
I found the Spitfire IA 100 octane was the worst aircraft for this effect, and it was prevented from getting over much more than 23,000 ft in a climb. At that altitude, it could not manage more than +0 boost/3000 rpm without misfiring. It was necessary to increase rpms to 3000 in order to register any kind of climb at that altitude.
Here are some samples of altitudes/boost levels/rpms when I got the onset of misfiring in the Spit IA 100 octane:
14,500 ft: +5 boost 2700 rpm
16,500 ft: +4 boost 2700 rpm
18,500 ft: +3 1/2 2700 rpm
20,000 ft: +2 boost 2700 rpm
21,000 ft: +1 boost 3000 rpm (as I got higher, I found reducing boost and increasing rpm was the best solution for max. climb)
22,000 ft: +1/2 boost 3000 rpm
The Hurricanes were much less likely to see this effect, in my experience, the only occasion I found the 100 octane Rotol Hurricane had this happen was at 2800 rpm/+6 1/4 boost at 16,500 ft, although I was not looking for the effect at the time, I had thought it was limited to the Spits, was just flying combat.
There was also another anomaly with the Merlins, in that there is a pronounced tendency to overheat sooner at higher altitudes. Flying at 2700 rpm/+1 boost at Sea level will see the engine operating at 85 C, but at 21,000 ft, using exactly the same boost and rpm and with the same radiator settings, temperatures will be up at 95 degrees. As anyone knows, temperature should be more easily controlled at higher altitudes, not the opposite.
I have been told others are getting different results, and it may be the installation, although my own wingman was also getting the effect, and many others have reported it.
As it stands, the Spitfires especially are still crippled for combat over approx. 12,000 ft, and do not achieve their historical climbs or speeds.
I plan to do some more testing tonight after verifying my Steam installation, deleting the cache and re-downloading the latest patch.
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