Safe MP & RPM ratios?

Max Cruise = 2400rpm 35"

 

Max Continuous = 2700rpm 46"

 

Military = 3000rpm 61"

 

If I were to run at, say, 2550rpm 41" (appx. halfway between m.cruise and m.continuous) would that be safe to run without causing damage?

 

Or doesn't it work like that?

Should be OK with radiators open.

If I were to run at, say, 2550rpm 41" (appx. halfway between m.cruise and m.continuous) would that be safe to run without causing damage?

 

Or doesn't it work like that?

Below maximum continuous you're safe with more or less whatever configuration you set. The problem would be overboosting for the rpm set but that means a lot of overboosting, not just 1 or 2 inches a few seconds or even some minutes. If you don't reach that overboosting point to stop the engine that only means extra wear for the engine in it's long term life so since you're is a sim with a brand new aircraft every time you hit fly it's no problem. There's even a situation in which some overboosting is desirable, that's low rpm, (somewhat) high MP, super economic cruising (which I don't know setting for the Stang, but we have ones for Spitfire and they work flawlessly like in RL).

 

Anyhow a different question would be, do you really need that setting given that engine manufacturer already told you the best performing ones? 24-36 is a good cruise setting balanced for best fuel consumption and speed, 27-46 a good fast cruise, best continuous climb, etc, and you're plenty of fuel in the Stang for usual sim missions even using max continuous all of the time. You can set 27 rpm and lower manifold whenever you need, avoiding the overboosting risk in most situation. 2550-41, well it's possible, just not the best for climbing, not the best for cruising, not the best balance between speed and full consumption, so just why? And here yes, that's how real aircraft engines work using manufacturer's settings most of the time.

 

May I recall some warbird pilot interview, as they lower engine settings all of the time in order to save some hours between expensive overhauls. Maybe I recall some setting like that mentioned, 26-42 perhaps or something like that, but the only reason to use it is warbirds use to be nimble with very little fuel load and useless equipment removed so don't need full power and they save money running the engine low, which is any of your problems in the sim so there's not much of a point in flying like that.

 

 

S!

Yeah, it's more out of academic interest rather than any practical (combat) value.

 

I've been speed testing the 51 under various throttle, RPM, oil, and radiator settings but I was never sure whether 'un-listed' MP/RPM combinations were actually harming the engine.

Yeah, it's more out of academic interest rather than any practical (combat) value.

 

I've been speed testing the 51 under various throttle, RPM, oil, and radiator settings but I was never sure whether 'un-listed' MP/RPM combinations were actually harming the engine.

Not really, listed config are just optimal but as said unless a bad overboosting for your setted rpm you're safe all of the time.

 

 

S!

In the back of the manual are some amazing charts that report all the different RPM/MP settings at all the altitudes from SL to 25k, depending on what range you need. It also gives fuel flow, true airspeed, and if the high blower should be on or off. Also, there are different charts for different aircraft weights, so you'll have to plan on how much fuel is used and switch to a different chart as you loose weight on fuel. There are also different charts for external payloads, so after you drop your ordinance/tanks there is a different chart for that too. IF you're interested in min/maxing.

 

Even if you don't plan on flying a 2000 mile round trip it will give you an idea of the relationship between MP and RPM so you'll be able to comfortably guess without being inefficient or breaking something.

 

Example:

If you want to travel at 20k ft with no range in mind (so max continuous), the chart tells me 2700RPM, 46MP, Hi blower on (AUTO), gallons per hour is 94, and true airspeed is 390mph or 340kts.

 

If you want to travel at 20k ft at max range, the chart says 2100 RPM, FT, Hi blower off (OFF) gallons per hour at 56, True airspeed is 315mph or 275kts.

 

If you want to travel 10k ft at max range (and no stores) the chart indicates 1600 RPM, 31MP, hi blower off (AUTO), for 47GPH at a true airspeed of 260mph or 225kts.

 

I guess you would have to do some flying to see what the actual MP when the chart says FT, but since you said your interest was academic, you sound like you want to do some experimenting. When I found these charts I spent a couple of weekends seeing what it was like. (Hint: VERY LONG AND VERY BORING, and if you have full tanks VERY TEDIOUS due to reversibility)

 

Also, the fuselage tank bug seems to not yet be fixed, so you won't be completely full on fuel in the immediate future, unfortunately.

Because Theodore is a scoundrel he forgot to mention the manual he speaks of is for the actual P-51D....not the DCS version.

 

http://www.wwiiaircraftperformance.org/mustang/P-51D-manual-5april44.pdf

Because Theodore is a scoundrel he forgot to mention the manual he speaks of is for the actual P-51D....not the DCS version.

 

http://www.wwiiaircraftperformance.org/mustang/P-51D-manual-5april44.pdf

 

OOPS important omission :(

Nice save!

You can run at any setting as long as you keep RPMs above throttle setting and keep an eye on water and oil temps. If ur temps get high you have to manually open the respective radiator because the auto radiators dont work.

You can run at any setting as long as you keep RPMs above throttle setting and keep an eye on water and oil temps. If ur temps get high you have to manually open the respective radiator because the auto radiators dont work.

auto radiators are working but auto curvature is set for minimal drag so most of the time at high power setting it will keep the highest temp as possible to reduce drag as much as possible so when you about to do couple turns and expecting big loss of speed open them manualy.(vertical climb for example)

at least that's what i noticed so far coolant temp stops just right before red line on auto so whne you do sudden change of speed radiator bulkhead transversal speed is not enought to prevent overheating

Edited April 5, 2019 by grafspee

Yah, what Grafspee is saying there. Auto works per se, but not in every conceivable situation, meaning you'll need to switch over to manual open occasionally.

Yah, what Grafspee is saying there. Auto works per se, but not in every conceivable situation, meaning you'll need to switch over to manual open occasionally.

 

yes just immagine that you diving after bf109 in p-51 and you keep your radiators auto thne you are about to hit 505mph limit speed so you retrac throttle so auto radiators start to closing bulkheads and suddenly bf109 going form dive to streight vertical climb so you are goint to full power and in to vertical climb with radiators shuts completly closed (it take good 20secodn to open them) you probably alredy know what will happen :) bf109 radiators open form 0 -100% in just a metter of 2-3 seconds maby

Your engine will also overheat in a sustained climb if you leave the radiators in auto. Temps can be all green when you start the climb and they will slowly increase over the red line for water and oil. Auto radiators won't open enough to cool the engine so you have to do it manually.

Edited April 10, 2019 by Snapage

Your engine will also overheat in a sustained climb if you leave the radiators in auto. Temps can be all green when you start the climb and they will slowly increase over the red line for water and oil. Auto radiators won't open enough to cool the engine so you have to do it manually.

 

i never encounter that problem i alwayes climbing at around 150mph and auto keeps temp at verge of overheating just below 120

but i never try climb in very hot day like above 30 celcius most of servers is using default 12 celcius or something close to it

i bet that control unit for cooling shuts had to be calibrated for difrent range of temps so while operating in winter it needed some adjustment as while running in hot summer too

Edited April 11, 2019 by grafspee

When i fly online, i never touched the Radiators Controll fly allways full Power 3000 RPM and 67HG 45-50% Fuel on the small BS Mission.

I barely encounter Engine Failures even without warming up the Engine.

When i fly online, i never touched the Radiators Controll fly allways full Power 3000 RPM and 67HG 45-50% Fuel on the small BS Mission.

I barely encounter Engine Failures even without warming up the Engine.

 

 

Depends what kind of flying you are doing, if you stay fast you wont have a problem but if you fly slow with high engine setting you need to manually open oil radiator and maybe water if it gets to high. You will overheat otherwise.

 

And in regards to WEP(67") the engine will fail at a random time after using it. Could be 10 minutes, 20mins 45mins into flight or u me be lucky and the engine may not fail for the duration of your flight. It can evwn break after you have landed and turned the engine off LoL.

 

I have heard the bang sound the engine makes when it insattly siezes after I have landed and shut down the engine. Then tried to start it and the prop wont move at all. Its happened to other peoples planes to when we have landed and talking about stuff after the our flight.

Depends what kind of flying you are doing, if you stay fast you wont have a problem but if you fly slow with high engine setting you need to manually open oil radiator and maybe water if it gets to high. You will overheat otherwise.

 

And in regards to WEP(67") the engine will fail at a random time after using it. Could be 10 minutes, 20mins 45mins into flight or u me be lucky and the engine may not fail for the duration of your flight. It can evwn break after you have landed and turned the engine off LoL.

 

I have heard the bang sound the engine makes when it insattly siezes after I have landed and shut down the engine. Then tried to start it and the prop wont move at all. Its happened to other peoples planes to when we have landed and talking about stuff after the our flight.

when engine dont want turn after lading and after some time waiting is most likly dead battery connect ground power and you will be fine

battery can provide power for lights and gages but not enough for starter

I keep radiator controls in auto always. It is so cold up there that even doing stupid things at FT isn't going to put you in the red (or only a little for a moment).

 

The manual says the WEP limit is 5 min at a time. The aftercooler is what you have to worry about overheating and there isn't a gauge for that. Also, ED has said they're doing a rework of warbird heat systems so the aftercooler heat might not be properly modeled.

 

I don't know about the 109 but I picked up the Dora9 a few months back. Just don't ever get into a dogfight with a Dora9 without your high blower on AT LEAST, if not above 20,000. That airplane is a dogfighting god. If you're flying against someone of a remotly close to equal skill the WEP ain't gonna save you.

I keep radiator controls in auto always. It is so cold up there that even doing stupid things at FT isn't going to put you in the red (or only a little for a moment).

 

The manual says the WEP limit is 5 min at a time. The aftercooler is what you have to worry about overheating and there isn't a gauge for that. Also, ED has said they're doing a rework of warbird heat systems so the aftercooler heat might not be properly modeled.

 

I don't know about the 109 but I picked up the Dora9 a few months back. Just don't ever get into a dogfight with a Dora9 without your high blower on AT LEAST, if not above 20,000. That airplane is a dogfighting god. If you're flying against someone of a remotly close to equal skill the WEP ain't gonna save you.

actualy when fighting pvp i use wep in p-51 to strech chase enough to get in to safe area and it works. at 61inHg you are 2-5 mph slower and bf109 catching up quickly maby 2-5 mph dont look much faster but in chase situation whne chased plane is 10mph slower or 5mph slower makes enormous difrence becouse you are doubling chase distance.

ofc 67inch will make you faster but until you hit critical alt for supercharger which is quite lower then 61" crit alt. 75" version would habe much lower crit alt so 75" would be limited to maby like 8k ft or something like that but you will gain couple mph more which wil add up to chase time or even make it get away chance :)

p-51 used for bomber escorts will not gain any benefit of using 150 fuel becouse they running above high blower crit alt but p-51's designated for low alt fighting would benefit form 150 fuel for sure

75" limit pobably wont change top speed at high alt but it will change top speeds in low or medium alts

as i know that merlin engine was one of the most durable v12 during ww2 and it is still used today for exeptional preformance and durability i dont know much about DB605 and its strenth but we have in dcs bf109 which it's engine never fail you can fly 1.8 ATA whole time not worrying about engine fail and another hand we got v-1650-7 which will brake in random time after using 67" i think something stinks here

i think that in dore you can use boost more often then in p-51.

for example griffon vs merlin maby griffon had more power but griffon required 3 times more often engine checks and reparing then merlin

Edited April 19, 2019 by grafspee

when engine dont want turn after lading and after some time waiting is most likly dead battery connect ground power and you will be fine

battery can provide power for lights and gages but not enough for starter

 

 

Its not a dead battery, the engine will randomly die after using WEP, even once on the ground and engine off. You can hear it die after engine is shutdown, its a loud bang.

 

 

 

I have no problem shutting down and restarting the P51.

Its not a dead battery, the engine will randomly die after using WEP, even once on the ground and engine off. You can hear it die after engine is shutdown, its a loud bang.

 

 

 

I have no problem shutting down and restarting the P51.

 

did you realy encounter this jamm bang while siting on ground with engine off ??

realy ??

I can confirm this has happened to me as well. No dead battery as I fire up the mustang in under 10 seconds each time. Does not happen all the time, in fact only recall it happening a couple times, but yes, you hear the same sound you normally hear for the lockup. Then when you go to start, it doesn't budge.

Yeah, my guess is that once you go WEP the engine is on a random countdown timer until it dies. Which makes it unusable unless you dont mind your engine seizing at a random time during or after a dogfight.

The same for Dora after using WEP with MW, after landing when engine was off, loud "bang" was heard and then engine wouldn`t start again. Propeller was jammed and did not rotate in any way.

It happened to me several times with D-9...

 

WEP seems to be common (and unsoved) problem for all planes in DCS which have this engine mode.

The same for Dora after using WEP with MW, after landing when engine was off, loud "bang" was heard and then engine wouldn`t start again. Propeller was jammed and did not rotate in any way.

It happened to me several times with D-9...

 

WEP seems to be common (and unsoved) problem for all planes in DCS which have this engine mode.

 

beside bf109 this one runs just fine i would say that it works way too good in bf109