Engine Sounds
SBDs, Stukas and Vals did just the opposite when they dived. The pilots throttled back to near idle to try and keep their dive speeds within acceptable limits.
Engine sound is dependent on RPM and manifold pressure and thus the decibel level and pitch of the sound for the very high pressure exhaust gas heard at the exhaust stacks. Our sound files replicated that very well. In the A6M5 Zero, the designers used this high pressure gas to augment the thrust of the prop by designing the stacks to actually provide a primitive form of jet exhaust at high manifold pressures. Compare the difference between the exhaust on the A6M2 and the A6M5 Zeros that come with CFS 2. I'm sure there was quite a difference in sound between the two models, although CFS 2 doesn't differentiate between the two with the original stock A6M2 sound file.
Prop sound: Prop RPM (much slower than engine RPM) has an impact on how we perceive an engine's sound with some planes like the De Haviland Beaver and the Hs 123 having very distinctive sounds, much like mini sonic booms coming off of the prop tips at max RPM on take off. Most WWII fighting aircraft had constant speed propellers (well modeled in CFS 2) and were used much like transmissions in your car to obtain either take off, combat or cruise performance. Higher prop RPM required a very shallow angle on the blades (much like 1st gear in your car) and very high angles of attack for cruising. Maximum prop RPM is limited because you have to keep the prop tips below the speed of sound. The larger the diameter of the prop, the lower its prop shaft RPM is when it reaches this limit. There were some experiments in the 1950s with a turboprop on the F-84 Thunder jet with a supersonic prop of small diameter. The project was quickly abandoned due to the high decibel level of the prop and many participants reported nausea due to the sound when standing near the plane when it was running.
Engine settings: When taking off, be sure to use max RPM (default setting in CFS 2) and when cruising to your target area, throttle down to about 2,000 to 2,300 RPM and you will hear the effect that you are looking for. Charles Lindbergh pioneered a very low RPM and a thin mixture for maximum range in the P-38 in the Pacific. You can also do this with CFS 2 by throttling down to 1,800 RPM or less and reducing your mixture until the engine just barely runs without cutting out. This is a very different sound from your max take off performance of about 2,800 RPM and max rich mixture. Watch your cylinder head temperature when running lean though as temperatures can begin to soar pretty fast. To cool things down, open your cooling gills or go to a richer mixture. Both techniques can get your engine back into the green. At any rate, the sound between cruise and take off engine sounds should be markedly different and, in fact, realistic.
Turbo/super charger sound: Another factor affecting perceived engine sound is that of the turbo or super chargers used on most WW II combat aircraft. Our sound engineers have done a pretty good job of getting this whining sound into our sound files, particularly with the German engines.
Boost: Several WWII fighters (and the FW 200 Condor) used either water or methanol boost at take off or during combat maneuvering. This too is modeled very well in CFS 2. The boost delayed detonation in the cylinders and thus allowed for higher manifold pressures. This can be clearly heard in CFS 2 when used. Unlike real engines that could be burned out quickly when using boost, our computers will withstand boost all day long!
Realism: While engine sounds are reproduced pretty well in flght sims, it will probably be pretty hard to get the feeling, vibration and sound of a 2,000 pound, 2,000 horse power engine reving at 2,000 RPM traveling at 300 knots with a 20 pound computer.
By the way, I remember that old Corsair sound file that gave you a whistling wind effect at high speeds. It was pretty cool. I'll look in my library and try and find it.
