Airshow Spit vs 109 - Youtube - In cockpit camera

[Blackdog_kt]

These however are the maximum permissible values for very short periods of time.
Actually running +6lbs boost is not that much lower than maximum continuous power.

For example looking at a Spit Mk.XIV/Griffon 65 pilot's handbook i have lying around, it is capable of +18lbs but only for 5 minutes (war emergency power). Maximum takeoff power is +12lbs when heavily loaded but it can takeoff with +7lbs as well, +9lbs can be used for 60 minutes on the climb out and the maximum continuous power is +7 lbs. Anything more than that will eventually heat the oil up to the point that it dissolves, lubrication is lost and the engine cooked. More or less similar limits were imposed on the Merlin engined variants as well.

This is not only applicable to the Spit, most aircraft of the time can't operate at full power for very long. For example, a 190 that is rated for 1.4 Ata at full power is limited to 1.2 Ata for continuous use, a P47 can go up to about 60" of manifold pressure but usually runs a good 15"-20" lower and so on.
Just another reason i'm eagerly awaiting SoW and a refined engine management model. No more Spit +25lbs going at full throttle for hours or 190s running 110%+WEP and resetting the overheat timer by popping the cowl flaps open every few minutes

If you want to see how much difference it makes try flying a Spit Mk.IX in IL-2 and limit yourself to using no more +7lbs, unless exceeding it for a couple of minutes at a time.