which coolant shutter position is best for mustang's speed?

[Dawncaster]

As far as I know, mustang's radiator effect is...

close to flush position = cooling bad but compression high and make high thrust with low drag. good performance.
close to wide-open position = cooling good but compression low and make low thrust with high drag. bad performance.

so, in my opinion, flush position had best performance or close, and automatic setting will choose flush position at close to max-speed.

but I'm not sure about it.

does anybody know detail?

 

[drgondog]

It wasn't a question of good or bad as coolant shutters never fully closed and never more than 7.5 inches 'open'. The coolant Temp of 100C, coolant shutter position at about 2-3" IIRC equated with near maximum airspeed. At full shut the IAS is about the same as full open - and about 10mph below optimal shutter opening.

At Takeoff and climb the shutter doors were usually near 'full open' as the airspeed wasn't sufficient to dump the oil and coolant temps.. at cruise and full throttle the coolant doors adjusted as required to maintain coolant temps at 100-107C and oil temps near 90C

It was all about maintaining proper coolant/oil temps and the manual shutter control was replaced with an auto control for both oil and coolant doors

 

[Dawncaster]

It wasn't a question of good or bad as coolant shutters never fully closed and never more than 7.5 inches 'open'. The coolant Temp of 100C, coolant shutter position at about 2-3" IIRC equated with near maximum airspeed. At full shut the IAS is about the same as full open - and about 10mph below optimal shutter opening.

At Takeoff and climb the shutter doors were usually near 'full open' as the airspeed wasn't sufficient to dump the oil and coolant temps.. at cruise and full throttle the coolant doors adjusted as required to maintain coolant temps at 100-107C and oil temps near 90C

It was all about maintaining proper coolant/oil temps and the manual shutter control was replaced with an auto control for both oil and coolant doors

auto control or not, it's not important for me.

I wanted to know was just best coolant shutter position for speed. there is no considerations for temps and even engine failure.

so, you mean

this flush position

and this full-open position

have same speed?

and flush shutter position has 10mph poor speed than optimal shutter position for maintain optimal temps?

I would like to know more detail about how it is possible, for FM.

as i see, mustang's rear scoop has enough size for thurst even with flush position.

 

[drgondog]

It may not mean much too you but full closed for a period of time means coolant burn over and you have to die, crash land or bail out if you override the auto control

http://www.wwiiaircraftperformance.org/mustang/P-51D_15342_Shutter_Calibrations.jpg

 

[Dawncaster]

! thanks! that is what I wanted.

Now, everything became clear.

P-51D had best performance with 15"

P-51H had best performance with flush position (7")

 

[drgondog]

You should note that the P-51D plots are at 2700 RPM and 46"Hg - a cruise setting meaning less mass flow rate through the system

 

[Dawncaster]

hmm.. "flush position" is fixed or variable by condition?

 

[drgondog]

flush condition is when lower surface of duct is aligned with the fairing.. there would be a gap between the lip of the duct and the lower fuselage - as you have depicted in your last three screen shots on the 51H above.