View Full Version : Throttle or Radiator?

06-03-2008, 03:03 PM
is it faster to run an aircraft at the highest throttle setting achievable without overheating but with the radiator open thus increasing drag or is it faster to run it with the radiator closed but at a lower throttle setting to prevent overheat or is there an optimum in between?

i would think it might vary from aircraft to aircraft but perhaps there is a general rule that could be applied across the board, also assume it is not in a dive and is in level flight


06-03-2008, 03:22 PM
This is quite easy to test using Level Stabiliser on Bombers ...and the answer is ....Well if I remember correctly most planes are about 10kmh faster at about 107% with rads fully open than at 99/100% rads shut...

06-03-2008, 03:31 PM
Sure, it will vary from aircraft to aircraft...

General rule?
Keep it cool... http://forums.ubi.com/groupee_common/emoticons/icon_cool.gif

And, switch on Complex Engine Management, so Prop Pitch comes into play... (not for all aircraft types though... some have it automated). For level flight speed and fuel effeciency this can be an important feature...

As for true speed?
Gain height... Trim the plane... keep it trimmed... Elevator, Aileron, Rudder. (once again, not for all aircraft types though... some don't have Aileron / rudder trim)

Meaning: Prop pitch and trimmed flight are way more important for speed than radiator is...
(Should you already be using both prop pitch and trim optimally, then ignore my post here http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif)

Have Fun!

06-03-2008, 03:41 PM
Yeah, like "Fool" said;

Try lowering the revs on one of those runs where you're going for best sustained speed.
The faster you run an engine, the hotter it runs. Fact of life there.

06-03-2008, 04:10 PM
Generally, top speed comes at top cost.

The throttle in itself is just a cog in the machine. The significance of 'full throttle' changes according to the circumstances...

'Full throttle height'.
This is the altitude at which MAP can no longer be maintained by advancing the throttle. MAP = Manifold Absolute Pressure.

Depending on what MAP you are trying to maintain, usually cruise pwr, ie. 75%, it will also be the height that the engine is at its most efficient, because the throttle bodies are wide open and the manifolds are breathing freely (no restrictions)

Actual Manifold Pressure varies with prop speed. So, full throttle height occurs at different altitudes depending upon rpm settings, and is of course different anyway for all of the different engine types.

Different aircraft achieve their maximum speeds at different heights.
You can find what they are by consulting 'IL2 Compare'. Find the link in Bearcat's sig.

As for cowl flaps, use them when you need to. That's it. Don't be afraid of them.

What was the question again? http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

06-03-2008, 05:36 PM
i usually run at max throttle with the radiator fully open, i do always trim my aircraft to the maximum but i dont use prop pitch as much as i should, i will try to do this more.

i was really just wondering if it would have been beneficial to actually close the radiator and reduce throttle but clearly the general consensus is that as a generalisation this is not the case

(btw i do already use il2 compare, and i agree that it is trully an invaluable tool) http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

06-03-2008, 07:13 PM
I find that I can often get more speed with @90-95% throttle and 90-95% pitch.. and a little nose down trim.