ORIGINAL: Sport_Pilot
The VP 20 pressure is varible, but I believe they claim the factory setting is about .25 PSI. They can be adjusted much higher. If you are using high nitro fuel the head will be less than 9'' of fuel at .25 PSI. Nitro is denser than water. 9'' is about the same as muffler pressure.
Sport Pilot,
What you write with nitro.
The head will be somewhere between 7.5 and 9 inches (20 and 24 cm) with 50 - 0 % nitro in factory setting
ideal .25 PSI but is independent of the power level, even when the engine is in idle.
Exhaust pressure depends on the power level and is never that high in midrange and for sure not in idle, that's the difference for the standard carburetor I think.
Cees