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"Dago Red uses a Merlin 622 power section with a Packard built V-1650-9 supercharger. The dash nine has optimal supercharger ratios for increased boost. This brings up the next question; how much boost does Dago Red run in a race? The quick and easy answer is; it all depends. During qualifying, only sufficient power is used to move up to the next round. However, when it gets down to the final Gold Race, everything is allowed to hang out. Maximum boost is primarily determined by engine rpm and secondly by ambient temperature and air pressure. In this engine it can run in the 135 to 140 in. Hg. range when at 3400 rpm. Assisting boost is a carefully designed ram air scoop. For Dago Red it is made from fiber glass with an ideal convergent/divergent design. This design picks up approximately 3 to 5 inches of manifold pressure at race speeds. Theoretically, it is possible to run an even higher manifold pressure than 140 in.Hg. Abs But at 140 inches the point of diminishing returns has been reached. In other words so much power is consumed driving the supercharger, very little, if any, additional power is fed to the propeller. At 140 inches, the Merlin two stage supercharger is consuming in excess of 1,000 horsepower to drive. It has even been argued that anything in excess of 100 inches does not produce any additional power to the propeller, however the aircraft will fly faster when running in excess of 100 inches. The argument presented is the fact jet thrust from the exhaust stacks is increased at the higher manifold pressure resulting in a higher air speed."
I was told the Japanese thought enough of the exaust thrust theory to use it in some aircraft, do you think the argument presented here is valid?
"Dago Red uses a Merlin 622 power section with a Packard built V-1650-9 supercharger. The dash nine has optimal supercharger ratios for increased boost. This brings up the next question; how much boost does Dago Red run in a race? The quick and easy answer is; it all depends. During qualifying, only sufficient power is used to move up to the next round. However, when it gets down to the final Gold Race, everything is allowed to hang out. Maximum boost is primarily determined by engine rpm and secondly by ambient temperature and air pressure. In this engine it can run in the 135 to 140 in. Hg. range when at 3400 rpm. Assisting boost is a carefully designed ram air scoop. For Dago Red it is made from fiber glass with an ideal convergent/divergent design. This design picks up approximately 3 to 5 inches of manifold pressure at race speeds. Theoretically, it is possible to run an even higher manifold pressure than 140 in.Hg. Abs But at 140 inches the point of diminishing returns has been reached. In other words so much power is consumed driving the supercharger, very little, if any, additional power is fed to the propeller. At 140 inches, the Merlin two stage supercharger is consuming in excess of 1,000 horsepower to drive. It has even been argued that anything in excess of 100 inches does not produce any additional power to the propeller, however the aircraft will fly faster when running in excess of 100 inches. The argument presented is the fact jet thrust from the exhaust stacks is increased at the higher manifold pressure resulting in a higher air speed."
I was told the Japanese thought enough of the exaust thrust theory to use it in some aircraft, do you think the argument presented here is valid?
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