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Originally Posted by TomcatViP
One Question Banks : when do you actually get max boost with a supercharged engine ?
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I suspect this is a hypothetical question: Highest boost possible boost is at lowest possible altitude at highest possible engine rpm with throttle valve fully open.
Highest allowed boost is available at with highest allowed engine rpm at all altitudes below full throttle height.
But really it's not about getting a high boost at low altitudes but make the engine survive the high boost. No one is telling that +17 boost didn't kill the engine.
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As I hve alrdy said, in the RR test manual the latter merlin is rated at 9lb of boost at 15kft not 12 or ...17
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So what is your point? There is a difference between "maximum-possible-boost-produced-by-the-supercharger-at-sea-level-that-the-engine-can't-handle-at-all" (around +17), "maximum-allowed-boost-in-case-of-emergency-for-no-longer-than-5-minutes" (+12 for 100octane fuel, +6 1/4 for 87octane fuel), "maximum-allowed-boost-for-no-longer-than-30 minutes" and "maximum-boost-for-infinite-time-...-well-not-infinite-as-your-engine-will-die-even-with-that-boost-after-200hrs-running-without-inspection"
There is no difficulty in getting a high boost at low altitudes from a supercharged engine. The difficulty are:
- Find the highest boost that does only acceptable "damage" to the engine and find ways to reduce the "damage" even further to permit (=allow) the use of higher boosts
- Find ways to maintain the high boost at high altitudes