Why Is The P-38 Lightning Manifold Pressure So Low

1st Official Post

    In other flight sims the P38 can run 54 inches of mercury at 100% power (without wep)
    I just took off from Sedona at 5000 feet and I was trying to adjust my ratio of manifold pressure to prop speed to and i noticed i was only getting 20 inches

    I was at full throttle, i tried to adjust things like rpm and mixture and nothing would increase it

    Why isnt the plane making full power?
    I understand many Warbirds nowdays are tuned down to reduce wear over time but i cant imagine that the total power would really be reduced by 3/5???? We’re really running on 2/5 power?

    Idk just thought that was weird i know ive asked about the p38 in here a few times but hopefully someone can help explain.

    If this is wrong then id suggest in the next update you guys increase the maximum engine power

    Not having secondary supercharging in American Warbirds reflects current operating practice. Have a look at this previous thread. Spitfires and Merlin P-51s have integral two stage supercharging so they would need high manifold pressures if ever introduced in Aerofly. The F4U Corsair had a complicated induction system.

    Thread

    What RPM produces the highest torque in the P-38 L-5

    Is RPM actually modeled properly outside of changing the RPM gauge? Does it affect the flight performance? Where do you guys research information about the plane when you created it? The RPM can go up to 2600 in the game but sources online say that the P-38s engines reach max torque at 3000 RPM and later models at 3400. Is there a reason that the P-38 in the game can’t go up to even 3000? Do you have information about it that suggests it can only go up to 2600? Does it not go higher because…
    ChuckMcPhuck
    July 25, 2025 at 1:06 AM
    • Official Post
    Quote from ChuckMcPhuck

    When will it be simulated? And cant you just increase the engine power data for the aircraft to match realism in the meantime? Like the aircraft doesnt NEED to be underpowered despite this

    The power output of the engine is already accurate at sea level. It's not underpowered, it has the correct horse power. It's just that it does this without being super charged or turbo charged, so performance drops faster with increasing altitude.

    Quote from Overloaded

    Not having secondary supercharging in American Warbirds reflects current operating practice. Have a look at this previous thread. Spitfires and Merlin P-51s have integral two stage supercharging so they would need high manifold pressures if ever introduced in Aerofly. The F4U Corsair had a complicated induction system.

    Thread

    What RPM produces the highest torque in the P-38 L-5

    Is RPM actually modeled properly outside of changing the RPM gauge? Does it affect the flight performance? Where do you guys research information about the plane when you created it? The RPM can go up to 2600 in the game but sources online say that the P-38s engines reach max torque at 3000 RPM and later models at 3400. Is there a reason that the P-38 in the game can’t go up to even 3000? Do you have information about it that suggests it can only go up to 2600? Does it not go higher because…
    ChuckMcPhuck
    July 25, 2025 at 1:06 AM

    If only we were talking about an aircraft with a secondary engine driven supercharger, rather than a turbosupercharger😉. Besides that, even if warbirds have their second stage supercharger disabled, the critical altitude of the first gear would usually still be somewhere between 5000 and 15000 feet.

    Quote from Jet-Pack (IPACS)

    The power output of the engine is already accurate at sea level. It's not underpowered, it has the correct horse power. It's just that it does this without being super charged or turbo charged, so performance drops faster with increasing altitude.

    Okay that makes sense, and the airplane definitely does not feel underpowered at sea level, however i am still confused why the manifold pressure even at sea level reads such a low reading. The displayed manifold pressure is directly representative of how much power the engine is currently making right? So at sea level shouldnt it read like 54 inches at max (not 60 since theres no wep)

    Quote from Martijn22

    If only we were talking about an aircraft with a secondary engine driven supercharger, rather than a turbosupercharger😉.

    The turbo-superchargers of the USAAF radial engines and the P-38’s Allison V-12 are still superchargers, the drive and control operation just differ. They were all remotely located from the engines as they required complicated air ducting and lots of space.
    Disabling the complexity of the turbo and waste-gates of the turbo aircraft would be the easiest given their physical separation. The mechanical superchargers would have required modification of the engines to simplify the supercharger operation but it was done in the interests of reliability and maintenance economy.

    The Aerofly P-38 has a manifold pressure of about 36 inches at full throttle at take off from sea level. If the aviation authorities approve that or a very similar maximum manifold pressure for civilian use in a de-rated engine with the turbo disabled, which they very well might do given the war time permitted boost being about twenty inches higher, the full throttle height would be at sea level. There would be no need to throttle back in the initial climb until reaching a height where holding the maximum manifold pressure corresponded with the throttles being fully opened.

    Without operating turbos there would be no critical altitude, the height where the engine’s automatic boost control has the waste gate fully opened.

    Quote from Overloaded

    The turbo-superchargers of the USAAF radial engines and the P-38’s Allison V-12 are still superchargers, the drive and control operation just differ. They were all remotely located from the engines as they required complicated air ducting and lots of space.
    Disabling the complexity of the turbo and waste-gates of the turbo aircraft would be the easiest given their physical separation. The mechanical superchargers would have required modification of the engines to simplify the supercharger operation but it was done in the interests of reliability and maintenance economy.

    The Aerofly P-38 has a manifold pressure of about 36 inches at full throttle at take off from sea level. If the aviation authorities approve that or a very similar maximum manifold pressure for civilian use in a de-rated engine with the turbo disabled, which they very well might do given the war time permitted boost being about twenty inches higher, the full throttle height would be at sea level. There would be no need to throttle back in the initial climb until reaching a height where holding the maximum manifold pressure corresponded with the throttles being fully opened.

    Without operating turbos there would be no critical altitude, the height where the engine’s automatic boost control has the waste gate fully opened.

    I was kidding about the discrepancy between superchargers and turbosuperchargers.😅

    But some ww2 turbocharged engines had a first stage engine driven supercharger, and a second stage turbo supercharger. My point was that the second stage could be disabled, leaving the first stage supercharger in operation. That first stage doesn’t necessarily need to have its critical altitude at sea level.

    In any case the Allison V-1710 -111 and -113, found on the P-38L models, have a second stage turbo supercharger according to this table: Allison Piston Engine Specifications. However I can’t find the critical altitude of the first stage, which may actually be at sea level.