Manifold pressure, RPM, and Fuel comsumption

[Spinout]

I have an annoying tendancy to run out of fuel only a few miles from base, so i did some offline testing trying to squeeze the most out of that last bit of gas.

What i found has me scratching my head a little.

P38: At max cruise setting 35"@2300rpm it went farther than wot@3000rpm, but not a whole lot. 35"@3000rpm went just as far as max cruise, but at a faster speed.  The funny thing is 32"@3000rpm went about 10% farther than max cruise while going the same speed (240mph)

F4U1D: max cruise 34"@2150 went about twice as far as wot@2700rpm. Using 41"@2700rpm went as fast as max cruise (280mph) but didnt go nearly as far. Using 44"@1800rpm (280mph) was also terribly inefficient.

Yak-9: similar to p38 in that it always went farther with rpms at 3000. Flying at reduced rpms always decreased efficiency.

Soooooooo, why is it that the p38 and yak seem to gain no benefit from reducing rpms? For both planes maximium range was obtained with ~25"@3000rpm. They never went as far with reduced rpms, at any man. pressure.

Anyway at leat i learned that my previous method of limping back to base at 200mph and minimum rpms was about as efficient as wot.

If anyone has more info on this, i'd love to hear it.

For those that care, heres my test method:

1. set a27 to bishop
2. select plane and 25% fuel
3. change FuelBurnMult (4 for yak, 5 for f4u, 5.5 for p38)
4. take off from a27, turn toward a16 and climb to 500ft.
5. accelerate at wot to test speed (250mph for p38, 275mph for f4u)
6. adjust rpm and man. pressure as desired
7.fly till it runs out of gas, using a16 as a rough measuring tool.

Its not extremely scientific, but i got very repeatable results.

[minus]

heh test the typhon  u will probably ...........  

if u reduce trotle  and rpm   the propeler create so  big drag the plane literaly stop at place      

[funked]

I have not done any controlled testing but my subjective impression has been that we are not getting any benefit from reduced RPM.

So I'm not sure why we have an RPM control.  I guess it is useful for fine power control when flying formation.

But for extending range I just reduce throttle and ignore the RPM now.

[Spinout]

Thanks for the input funked.

I played around some more and got the impression that the max cruise settings work well in the F4U, P47 and P51, moreso than just reducing throttle.

But in other planes reducing rpm is pretty much a craps shoot. It might save gas or it might burn it faster than wot.

To be on the safe side, just reducing throttle always extends range to some extent.

BTW, can someone tell me if there is a dot command to change altitude offline. I've seen some screen shots implying that it can be done.

[funked]

I have some pretty good data on fuel flow rates for Fw 190A at different RPM and MP and I will try to do a legit test tonight.

[Rocket]

In the hawg I run low manifold pressure and low RPM and fly for days in the MA.  Try 1300RPM and 34"  (can't remember exact setting off the top of my head and can't go in and fly till I get the new system).  This keeps me ticking along at about 200IAS +/- and has gotten me home safely a number of times.  If you want to conserve fuel you have to slow down to do it I have found.

S!
Rocket

[Jigster]

 

Originally posted by Spinout:
Thanks for the input funked.

I played around some more and got the impression that the max cruise settings work well in the F4U, P47 and P51, moreso than just reducing throttle.

But in other planes reducing rpm is pretty much a craps shoot. It might save gas or it might burn it faster than wot.

To be on the safe side, just reducing throttle always extends range to some extent.

BTW, can someone tell me if there is a dot command to change altitude offline. I've seen some screen shots implying that it can be done.

You need to use the wind command. Take off in the desired direction, and when ya get set, type in .wind (the heading in 3 numbers, 0-360 degrees) (the altitude) (the speed of the wind) (updraft)

for offline I normally go .wind 0 0 0 127 (127 is max)

This will put you at 30k in just a min or two.

You can get well over 100k if ya try, although things start looking weird  

When ya get good you can try it on the ground and pretend your a harrier

- Jig

[wells]

Just did an offline test..

Reducing rpms has NO effect on fuel consumption.  All it seems to do is add drag and slow you down.

[Spinout]

LOL Jig that is hilarious! A p38 with engines off felt like i was playing LHX Attack Chopper again  

Rocket, while that setting may keep you in the air a long time, i think u will actually go farther if you use the max cruise setting of 34"@2150rpm (or less throttle at 2700rpm).

Thanks wells, that was sort of the impression i got but couldnt say for sure. It seems like we are getting the reduced power output from reducing rpms (power=torqueXrpm) but not the reduced fuel consumption.


[This message has been edited by Spinout (edited 08-30-2000).]