Hitech/Pyro, calibration of the MAP-gauges in AH.

[Wmaker]

For the planes that have their manifold pressure given in inches of mercury show 10 inHg value at all altitudes both when the engine is shut down or the throttle is pulled to idle. Normal accepted standard athmosphere has a pressure of 29,92 inHg at sea level. So for US planes and the planes in general which use inches of mercury MAP-gauges the gauges should read ~30" when the engine is shut down at a sea level field. For British and Japanese planes the MAP-gauges were calibrated to read 0lbs/sqin and 0mmHg respectively at sea level.

It would then be cool if this lower end of the MAP scale would change in relation to altitude just like the upper limit does. For example, engine shudown at a field that is at 3000ft high the MAP gauge would read approximately 27inHg.

So, I think this would add to the fidelity of the simulation.

[kvuo75]

i was gonna ask for this some time ago but I figured people would just say "it doesn't really matter"..

but  nevertheless.

[Delirium]

I always thought it was set up that way because it was easier on the average user. The compass is set up for ease of use as well and isn't accurate.

[hitech]

If the prop is still turning the same rpm with mags on or off the MP would not change.

HiTech

[Wmaker]

If the prop is still turning the same rpm with mags on or off the MP would not change.

Hmm...now I don't quite understand? AH's WWII aircraft have constant speed props and due to that RPM tends to stay constant during normal flying but throttle controls pressure of the charge that is being fed to the cylinders? I must have somehow misunderstood your post HT.

At rest, engine shut off, prob stationary...shouldn't the MAP-gauge show the current ambient air pressure at the time?

Brits and the Japanese used a system where a pressure that was below the normal standard sea level air pressure shows as "negative pressure", because the base line for zero is set at sea level. These negative values or below 30" values for US planes would usually only occur at higher altitudes and low power settings obviously but it would be cool that the MP-gauge wouldn't always return back to the 10" when throttle is pulled back but would show the correct pressure for idle for example.

I always thought it was set up that way because it was easier on the average user.

I don't see how showing correct manifold pressures at all modes of operation would make it any more harder for average user.

[JUGgler]

For the planes that have their manifold pressure given in inches of mercury show 10 inHg value at all altitudes both when the engine is shut down or the throttle is pulled to idle. Normal accepted standard athmosphere has a pressure of 29,92 inHg at sea level. So for US planes and the planes in general which use inches of mercury MAP-gauges the gauges should read ~30" when the engine is shut down at a sea level field. For British and Japanese planes the MAP-gauges were calibrated to read 0lbs/sqin and 0mmHg respectively at sea level.

It would then be cool if this lower end of the MAP scale would change in relation to altitude just like the upper limit does. For example, engine shudown at a field that is at 3000ft high the MAP gauge would read approximately 27inHg.

So, I think this would add to the fidelity of the simulation.

Will this make it easier for me to make a ham sandwhich?



JUGgler

[Chalenge]

I think the answer would be that not all of the gauges are measuring pressure in inches of mercury.

[Wmaker]

I think the answer would be that not all of the gauges are measuring pressure in inches of mercury.

Nope, that's not the answer.

[Wmaker]

These negative values or below 30" values for US planes would usually only occur at higher altitudes and low power settings...

The above isn't correct, sorry. Brainfart.

The MAP can indeed be lower than the ambient air pressure as the engine starts and runs on idle due to the suction of the pistons and the low amount of fuel/air going to the cylinders. What the pressure exactly is at idle obviously depends on the engine and I can imagine that these values aren't as easy to find for many of these planes as the MAP at higher power settings and that is maybe one good reason to keep the figures at "default" so to speak. But even then, it would be nce to see ambient air pressure in the gauge when the engine is shut off.

[Chalenge]

Which airplane are you testing with?

[kvuo75]

If the prop is still turning the same rpm with mags on or off the MP would not change.

HiTech

he means when the engine is stopped. MP should show ambient pressure.

[hitech]

he means when the engine is stopped. MP should show ambient pressure.

He stated many things about the MP. I don't disagree that the MP reads ambient when the engine is stopped and gauge switch is on. I'm not sure it's really worth the time to make the gauge read correctly when nothing is happening.

HiTech

[EskimoJoe]

He stated many things about the MP. I don't disagree that the MP reads ambient when the engine is stopped and gauge switch is on. I'm not sure it's really worth the time to make the gauge read correctly when nothing is happening.

HiTech

It probably isn't.

[Wmaker]

He stated many things about the MP.

If there's more errors there than the one I mentioned, feel free to correct. I certainly aren't a big expert whe it comes internal combustion engines...or any kind of engines for that matter.

I don't disagree that the MP reads ambient when the engine is stopped and gauge switch is on. I'm not sure it's really worth the time to make the gauge read correctly when nothing is happening.

Ok, that's fair enough.