Author Topic: Mustang Pilots  (Read 187 times)

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Offline _AH_Bear

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Mustang Pilots
« on: April 20, 2020, 06:21:10 PM »

Offline _AH_JimDandy

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Re: Mustang Pilots
« Reply #1 on: April 21, 2020, 11:14:37 PM »
This is a great video Bear, I have a bunch of notes taken down from this video.
I was just curious about the mixture at 50% is better then mixture at 70% continuous automated.
I would like to give this a bunch of testing on this. I have read a lot and a lot of P51 pilots say
to run at 70%. Sort of set it and forget it.  Would like to hear what all the Mustang drivers think about
this. Thank again for video Bear.

JD

Offline _AH_Hollywood

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Re: Mustang Pilots
« Reply #2 on: April 22, 2020, 10:06:02 PM »
I’ve seen this video as well JimDandy.

The majority of the Mustang is automatic. If you set the mixture to 70% you are basically setting it to auto. That’s what the actual manual says. Set to “Run”

Do you get more performance if you set it to 50%?  I can’t see that rational but perhaps smarter guys like Shrt and Twenty can chime in. 
Leaner mixtures would make the engine run hotter and perhaps get better fuel economy but more performance, I can’t figure that.

The manifold pressure gauge is the true indication on the power of the engine so if you lean the engine do you see an increase in MP. Don’t think so.


One thing I can share to get the most out of your Stang, is to close the oil shutter.  You can pick up some extra MPH that way. But be careful, you can damage your engine. Twenty and I have used this trick to hunt down 262s.

It is surprising that that small shutter can cause so much parasitic drag when open. 

The water Rads don’t have the same result. 
Meredith Effect is a known Phenomenon

Quote
The North American P-51 Mustang makes significant use of the Meredith effect in its belly radiator design.
The Meredith effect is a phenomenon whereby the aerodynamic drag produced by a cooling radiator may be offset by careful design of the cooling duct such that useful thrust is produced. The effect was discovered in the 1930s and became more important as the speeds of piston-engined aircraft increased over the next decade.

The Meredith effect occurs when air flowing through a duct is heated by a heat-exchanger or radiator containing a hot working fluid such as ethylene glycol. Typically the fluid is a coolant carrying waste heat from an internal combustion engine.[1]

The duct must be travelling at a significant speed with respect to the air for the effect to occur. Air flowing into the duct meets drag resistance from the radiator surface and is compressed due to the ram air effect. As the air flows through the radiator it is heated, raising its temperature slightly and further increasing its volume. The hot, pressurised air then exits through the exhaust duct which is shaped to be convergent, i.e. to narrow towards the rear. This accelerates the air backwards and the reaction of this acceleration against the installation provides a small forward thrust.[2] The air expands and decreases temperature as it passes along the duct, before emerging to join the external air flow. Thus, the three processes of an open Brayton cycle are achieved: compression, heat addition at constant pressure and expansion. The thrust obtainable depends upon the pressure ratio between the inside and outside of the duct and the temperature of the coolant.[1] The higher boiling point of ethylene glycol compared to water allows the air to attain a higher temperature increasing the specific thrust.

If the generated thrust is less than the aerodynamic drag of the ducting and radiator, then the arrangement serves to reduce the net aerodynamic drag of the radiator installation. If the generated thrust exceeds the aerodynamic drag of the installation, then the entire assemblage contributes a net forward thrust to the vehicle.

The North American P-51 Mustang, which first flew in 1940, adopted both the Merlin engine and the Meredith principle.[3]

Around this time the Meredith effect also inspired early American work on the aero-thermodynamic duct or ramjet, due to the similarity of their principles of operation.[1]
Wikipedia

Interesting to see others comments.

HW
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Offline _AH_Lippy

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Re: Mustang Pilots
« Reply #3 on: April 26, 2020, 04:00:29 PM »
I was watching a documentary on the stang. It also confirmed that the heat from the radiator would produce enough outbound thrust from the heated air to offset any drag.