More power at lower RPM? M-105PF

[Boaty-McBoatface]

I'm interested to know how the M-105PF makes 1240hp at 2550RPM and only 1210hp at full 2700RPM? Once at altitude there is no longer this discrepancy and full power is at the full 2700RPM.

 

Also, since LaGGs have the exact same engine, why is this discrepancy not the same?

 

As far as I know there was no detail mentioned about these changes in the patch notes or developer diary.

Edited January 10, 2017 by B0SS

[Finkeren]

A question of propeller.

[Boaty-McBoatface]

A question of propeller.

No. Power output at the crank has nothing to do with propeller.

Edited January 11, 2017 by B0SS

[Brano]

Supercharger at 1st stage IIRC.

[JG13_opcode]

I'm interested to know how the M-105PF makes 1240hp at 2550RPM and only 1210hp at full 2700RPM? Once at altitude there is no longer this discrepancy and full power is at the full 2700RPM.

 

Also, since LaGGs have the exact same engine, why is this discrepancy not the same?

 

As far as I know there was no detail mentioned about these changes in the patch notes or developer diary.

Where are these numbers from?

[JtD]

Generally, at high RPM the combustion in the engine gets more inefficient, so it starts losing power at some point. It's true for all engines. You can look at the power curve of your car, if you like. For the M-105 this point is 2550rpm.

 

The reason the M-105 does no longer develop more power at 2550rpm than at 2700rpm at altitude, is because the effectiveness of the supercharger is depending on the engine rpm. High rpm mean more supercharging, which at low altitude is just wasted or even counter-productive, but at high altitude in the thin air every bit of supercharging helps. So at higher rpm at high altitude, the engine will work at higher manifold pressures and generate more power this way.

This is engine specific and it's valid for Yak, LaGG and Pe-2 and any other plane that has the M-105PF.

[Boaty-McBoatface]

The reason the M-105 does no longer develop more power at 2550rpm than at 2700rpm at altitude, is because the effectiveness of the supercharger is depending on the engine rpm. High rpm mean more supercharging, which at low altitude is just wasted or even counter-productive, but at high altitude in the thin air every bit of supercharging helps. So at higher rpm at high altitude, the engine will work at higher manifold pressures and generate more power this way.

This is engine specific and it's valid for Yak, LaGG and Pe-2 and any other plane that has the M-105PF.

Great answer thanks. The Lagg specifications list 2700RPM for maximum power at low altitude, different from yak series, yet the same engine. I don't know what's going on there.

 

I've never seen another aircraft engine list the maximum power at a lower RPM than max like this M-105PF. Seems a little odd.

Edited January 11, 2017 by B0SS

[=TBAS=Sshadow14]

yes where are you getting these numbers from ??
I see no in game display for this..

Also if the fuel system cannot supply enough fuel to run stoich at at lower altitude it will run lean and loose power
Once it gets higher and air density drops the fuel system is ok.

[jaydee]

Someone correct me if I am wrong ? Most engines make Maximum Torque before  they reach Maximum Power Output. If we bring we bring Prop-Pitch down at Full Throttle we get into the Maximum Torque of the Engine, which will give a trimmed aircraft maximum speed. If we want to Climb quickly we need Maximum Power !

I have spent a few hours in the IL 16 lately and I've found about 80-85% PP gets me top speed whilst trimmed !

As someone said above it is the Propeller combined with the engine !

~S~

[1PL-Husar-1Esk]

I have tested Mig3 to gain more speed in level flight by reducing RPM on max MP in theory it should coarse the propeller and hence gain speed but to no avail. Why?

[Boaty-McBoatface]

yes where are you getting these numbers from ??

I see no in game display for this.

Dude these numbers are available anytime in game when you bring up the map/briefing. How could you miss it?

 

Here is the developer diary post for the specs:

 

https://forum.il2sturmovik.com/topic/25993-aircraft-flight-and-technical-specifications-and-operational/?p=406720&do=findComment&comment=406720

Edited January 11, 2017 by B0SS

[=TBAS=Sshadow14]

Those are the numbers written in the specs page..

I was talking about what they actually achieve on maps.

What temp?
What Air Pressure?
What Airfield Altitude or MSL?

Edited January 11, 2017 by =r4t=Sshadow14

[Boaty-McBoatface]

Those are the numbers written in the specs page..

 

I was talking about what they actually achieve on maps.

 

What temp?

What Air Pressure?

What Airfield Altitude or MSL?

What on earth are you on about? Engine power figures are corrected for international standard atmospheric pressure. They are standardized measurements.

 

You can find them for any engine of any airframe on the sim.

Edited January 11, 2017 by B0SS

[Brano]

To add to JtDs post.For Yak-1 with M105PF there is one more interesting issue. According to Stepanec,its propeller had optimum efficiency below 1st critical altitude at 2600rpm. When using 2700rpm,it went a bit out of this optimal zone (prop blade AoA) As Im not aeronautical engineer,I try to look at things from combat pilot perspective. In reality using 2600 rpm low on deck gave you increase of max continuous horizontal speed of 6-7km/h faster then with 2700rpm.From the practical point of view it had negligible advantage.For climbing you had to go for 2700rpm to get best climbing values. You better watched that your radiator flaps are set correctly and your canopy closed. Here you could lose up to 60km/h of your speed.

LaGG-3 s.29 used different prop (VISh 61) which might have optimal efficiency at 2700rpm down low. I can check with tech.manual when back home.

[Boaty-McBoatface]

To add to JtDs post.For Yak-1 with M105PF there is one more interesting issue. According to Stepanec,its propeller had optimum efficiency below 1st critical altitude at 2600rpm. When using 2700rpm,it went a bit out of this optimal zone (prop blade AoA) As Im not aeronautical engineer,I try to look at things from combat pilot perspective. In reality using 2600 rpm low on deck gave you increase of max continuous horizontal speed of 6-7km/h faster then with 2700rpm.From the practical point of view it had negligible advantage.For climbing you had to go for 2700rpm to get best climbing values. You better watched that your radiator flaps are set correctly and your canopy closed. Here you could lose up to 60km/h of your speed.

LaGG-3 s.29 used different prop (VISh 61) which might have optimal efficiency at 2700rpm down low. I can check with tech.manual when back home.

OK mate thanks for checking. I agree rads and other factors are much more relevant to maximum performance. Still I find this discrepancy worth discussion.

 

Prop still shouldn't have any effect on maximum power output. The prop merely determines how that power is transferred. Lagg should still have same power stats.

[Brano]

According Gavric on russian forum,during the work on Yak-1 s.127 FM, they got into their hands document from TsIAM (Central Institute for Aviation Engines) trials of M-105PF engine. It showed that on low altitude below critical altitude the max power output of engine was really around 2600rpm,not at 2700rpm. Together with the prop effect I mentioned above,they have adjusted this for the engine of Yak-1 s.69 and released in version 2.004. Unfortunately discussion went different way and question about this effect being implemented also for LaGG-3 was not answered.

 Maybe it was easy to do for Yak,but would require much more time for LaGG-3. And for the Yak they had confirmation of this effect in reality thanks to excellent book from A.T.Stepanec about ''how to squeeze your yak to max''.

At the end,the effect is nice to have,but really nothing to kill oneself over if it is not there for LaGG 

[Boaty-McBoatface]

Brano that's really interesting dude.

 

That book sounds incredible.

[=TBAS=Sshadow14]

Th

 

What on earth are you on about? Engine power figures are corrected for international standard atmospheric pressure. They are standardized measurements.

You can find them for any engine of any airframe on the sim.

They are not standard when in USE only on paper.
(The standard number ONLY applies if you are flying in those conditions generally a lab, just like car figures for L/100km(miles per gallon), They are Impossible to replicate in real world conditions as the tests are too controlled.)

They(planes & engines) are Effected by each maps Weather (Temps and Air Density)
Hence why on 30+*C Maps in the summer (Thinner Air) the BF110 barely manages to make 200kph for take off (flaps needed + Max power + Holding brakes is best till max thrust)
Where as on the same runway Length and procedures with weather set to -25*C (Denser Air) It takes off much sooner and easier (no flaps and only 85% power needed and very easy low effort rotation @ 200kph)

You Cannot just read the stat card and say of thats what the plane will do ingame Exactly.(need Science not Faith)
A, You have to test it yourself (at a given alt, temp, density) But as there is no way to measure actual output figures properly they are not shown ingame and there is no WEB API to Read them on the fly while testing.
(hp, thrust, and so on) we must take the devs word for it.

B, Just because the devs write on stat card a planes max speed = xxx.xx does not mean it has to or they not allowed to lie about it (no law saying it must be true,)

The devs are allowed to for marketing (just like almost all companies do)
- state that plane A can go 1,000kph maximum speed even if that can only be replicated in a specially setup map for the test with correct weather in which players will never see
(just like when you buy a new car you will NEVER get the quoted power output from the book)
 

Edited January 12, 2017 by =r4t=Sshadow14

[LukeFF]

B, Just because the devs write on stat card a planes max speed = xxx.xx does not mean it has to or they not allowed to lie about it (no law saying it must be true,)

 

The devs are allowed to for marketing (just like almost all companies do) - state that plane A can go 1,000kph maximum speed even if that can only be replicated in a specially setup map for the test with correct weather in which players will never see (just like when you buy a new car you will NEVER get the quoted power output from the book)

 

 

I'd take another close look at the forum rules before making a statement like that again.

Edited January 12, 2017 by LukeFF

[Boaty-McBoatface]

Th

 

They are not standard when in USE only on paper.

(The standard number ONLY applies if you are flying in those conditions generally a lab, just like car figures for L/100km(miles per gallon), They are Impossible to replicate in real world conditions as the tests are too controlled.)

 

They(planes & engines) are Effected by each maps Weather (Temps and Air Density)

 

 

This entire post is complete and utter crap! Good grief man, what the hell do you think you're on about?

 

Power figures are of course dependent on atmospheric conditions and other controlled factors. That is exactly the purpose of such figures - controlled benchmarks to record and gauge some sort of a comparison in standardized conditions.

 

I don't know why I'm bothering with this - you've deliberately gone off on a wild tangent from the purpose of this thread. What the bloody hell is your point?

 

Also, you do realise this codswallop you're posting is a blatant violation of the forum rules?

Edited January 12, 2017 by B0SS

[=TBAS=Sshadow14]

Must be some missing text now showing for me or maybe a language barrier

There is only stats listed on that link and no mention of test conditions and if they are all Exactly the same the fact that stall speeds are listed in Brackets means that the test are not the same otherwise stall speeds would be identical. not 25kph variation.


 

[jaydee]

This entire post is complete and utter crap! Good grief man, what the hell do you think you're on about?

 

Power figures are of course dependent on atmospheric conditions and other controlled factors. That is exactly the purpose of such figures - controlled benchmarks to record and gauge some sort of a comparison in standardized conditions.

 

I don't know why I'm bothering with this - you've deliberately gone off on a wild tangent from the purpose of this thread. What the bloody hell is your point?

 

Also, you do realise this codswallop you're posting is a blatant violation of the forum rules?

 

Boss,may as well bang your head on the wall talking to him. ~S~

[Dakpilot]

Must be some missing text now showing for me or maybe a language barrier

 

There is only stats listed on that link and no mention of test conditions and if they are all Exactly the same the fact that stall speeds are listed in Brackets means that the test are not the same otherwise stall speeds would be identical. not 25kph variation.

 

 

 

 

 

Tests are done in ISA 

 

https://en.wikipedia.org/wiki/International_Standard_Atmosphere

 

The Autumn map is set up at 15 degrees C/ISA and is generally used for 'player' testing

 

All aircraft have had a lot of work to get performance figures within 5% of RL figures (stated Dev aims) for identical aircraft/engine spec, when people find any of these figures to differ by a larger margin long 'conversations' happen in the FM section

 

overall the aircraft are pretty close to correct with a few outliers which are hopefully being fixed, creating FM is not easy of flawless in computer simulation

 

by using ISA aircraft performance figures can (generally) always be compared and predicted even at different temps pressures and altitudes because the deviations are a known constant

 

The FM of aircraft is very complex to get turn times/ climb times top speeds etc correct, if one parameter drag/weight/HP/lift etc. etc is wrong the performance will be wrong and easily noticeable 

 

If you read DD #138 by An Petrovich (and some of his other posts) and Gavrick DD # 140 it will give you an adea how seriously they take FM modelling

 

https://forum.il2sturmovik.com/topic/168-developer-diary/page-4

 

Cheers Dakpilot

Edited January 12, 2017 by Dakpilot

[Brano]

Brano that's really interesting dude.

 

That book sounds incredible.

  The book is freely available on internet. Dont have link right now at hand. But beware,its in russian.

What I see as awsome on this book is the way it is written. Its for average combat pilot. Not an academic wall of encrypted text and weird formulas.

Its title is self explanatory = Kак получить наилучшие летние данные на самолете Як  (How to achieve the best flying conditions for Yak ) 

 

It explains lots of things in a coherent way (not skipping from topic to topic) and gives many hints how to achieve the best speed/climb,how to optimise fuel consumption,work with mixture,radiators and other aircraft systems etc. It also comments on those hints explaining why things work like this and not like that.

 While its focus is on Yaks equipped with MP105PF engines,the content explaining general terminology can be freely extrapolated to any other fighter plane.

 

A must read for any VVS fighter pilot....and as a trophy book, also for LW 

[unreasonable]

  The book is freely available on internet. Dont have link right now at hand. But beware,its in russian.

What I see as awsome on this book is the way it is written. Its for average combat pilot. Not an academic wall of encrypted text and weird formulas.

Its title is self explanatory = Kак получить наилучшие летние данные на самолете Як  (How to achieve the best flying conditions for Yak ) 

 

It explains lots of things in a coherent way (not skipping from topic to topic) and gives many hints how to achieve the best speed/climb,how to optimise fuel consumption,work with mixture,radiators and other aircraft systems etc. It also comments on those hints explaining why things work like this and not like that.

 While its focus is on Yaks equipped with MP105PF engines,the content explaining general terminology can be freely extrapolated to any other fighter plane.

 

A must read for any VVS fighter pilot....and as a trophy book, also for LW 

 

Is that the same as this by LtCol Stepanets?

 

http://www.airpages.ru/dc/doc100.shtml

[Brano]

Yes,thats the book.

[unreasonable]

Great - having a read now.

 

Right clicking and translating in Chrome gives something that is just about comprehensible in English, if you persevere. (eg canopy = "lamp" etc) 

 

edit: I really need this for Juri's campaign "Ivan's War" - at the moment I feel very like one of the hapless novice pilots.

Edited January 12, 2017 by unreasonable

[Mesha44]

What a great link, thanks.  I will have to try to read through some of that material.  There is so much stuff there.