Lower Mixture = Overheating

[Livai]

Found Very Perfect Inlet and Outlet cowl shutters Settings for my La-5 to keep the Engine cool and the Top Speed very high for summer and autumn maps. Perfect to surpass the Fw-190, to climb fast or to run away fast. All seems perfect to have fun but if I try to lower the Mixture to save some fuel the Engine start to Overheating! If I raise the Mixture back the Engine cools down!
With a lower Mixture should the Engine cool down + save some fuel where the Engine runs not at his full power. Ok, I lose maybe a little speed if the Engine not runs at his full power but I needed to save some fuel to my target. The side effect should lower the Engine Temperature, great to have. But that was just a dream! The reality is I need to fly full power to keep the Engine cool waste fuel for nothing. And if someone here say come one Lower Mixture + Open more Inlet and Outlet cowl shutters to be solution.... No its not. Open more Inlet and Outlet cowl shutters means I lose more Speed for what, at straight level flight, at Top Speed???

[216th_Jordan]

nope, if the mixture is too low in fact the engine will overheat, just like in real life.

in a rich mixture a part of the heat from combustion is taken out of the engine by the unburned fuel.

[Livai]

nope, if the mixture is too low in fact the engine will overheat, just like in real life.

in a rich mixture a part of the heat from combustion is taken out of the engine by the unburned fuel.

 

Good to known. The Engine started to overheat with Best Power Settings already. With Enriched the Engine not overheat? All happens at Top Speed and a straight level flight. I was confused because I learned from this video? Thats why I posted!

 

https://www.youtube.com/watch?v=UoADOlgfW6Q

Edited January 17, 2016 by Superghostboy

[Dakpilot]

As Jordan says above, this is how it works in real life

 

An easy and extreme example of the principle is in Racing motorbike Two stroke engines, the leaner (lower) the mixture is the more power you get, however too lean and the engine will seize very quickly due to rapid overheat.

 

In an aircraft the mixture must be set to within limits for whatever altitude you are flying, there is no other way, too high (Rich) mixture at altitude will lose power (all dependent on type of fuel delivery system)

 

Cheers Dakpilot 

[6./ZG26_5tuka]

Good to known. The Engine started to overheat with Best Power Settings already. With Enriched the Engine not overheat?

Many aircraft engines are designed to inject more fuel into the cylinders than can be bruned at full rich mixture setting. That way the unburned fuel has a cooling effect and prevents the engine from overheating during climbs.

 

"Combat setting" basicly means you inject just as much fuel into the cylinders as can be burned completely without any excess fuel. That way you can acchieve more power output but lack the additional cooling effect.

[Bando]

I used to look outside to see the colour of the exhaust to determine where the mixture lever should be. Now it's impossible to see the exhaust, I wonder if some of you can give any tips on how to read the instruments to determine the right mixture, as I'm baffled.

[6./ZG26_5tuka]

For some reason mixture changes between 100 and 60% won't be indicated on MP gauges for the Lagg-3, La-5 and Yak. It works fine for the Mig though.

[Jizzo]

For some reason mixture changes between 100 and 60% won't be indicated on MP gauges for the Lagg-3, La-5 and Yak. It works fine for the Mig though.

What exactly do you mean?

[6./ZG26_5tuka]

Get in one of those former mentioned planes and try 60, 70, 80, 90% ect mixture at constant throttle and you'll not see any difference in MP. In the Mig however MP increases when enriching mixture and drops when leaning it.

Edited January 17, 2016 by Stab/JG26_5tuka

[JtD]

That's because the MiG-3 has a different engine control system.

[216th_Lucas_From_Hell]

Is this behaviour present in the Il-2 as well, or does the AM-38 use a different system?

[JtD]

It's basically the same engine with a different supercharger. Quite possible the same controls, haven't checked yet, can't do right now.

[6./ZG26_5tuka]

That explains the difference. Still question remains how russian pilots managed to set their mixture accordingly. I doubt they stacked their heads out looking for exhaust flame colours.

[6./ZG26_Klaus_Mann]

That explains the difference. Still question remains how russian pilots managed to set their mixture accordingly. I doubt they stacked their heads out looking for exhaust flame colours.

Haptics. You feel the engine in your ass, wether it stutters (too high), vibrates (too low) and so on. You learn it.

 

Anyways, on our Lycoming with 140 PS we removed old soot and oil from the valve seats by giving it full throttle and leaning it out. This can get the exhaust manifold glowing hot, but you feel it. 

[Fidelity]

That explains the difference. Still question remains how russian pilots managed to set their mixture accordingly. I doubt they stacked their heads out looking for exhaust flame colours.

Sound and feel. If the mixture setting is wrong by a good amount the RPM needle should bounce as well.

[6./ZG26_5tuka]

Sound and feel. If the mixture setting is wrong by a good amount the RPM needle should bounce as well.

Thats very well simulated in RoF although it's completely different planes / engines. Sad it's not as nicely done in BoS/BoM.

Haptics. You feel the engine in your ass, wether it stutters (too high), vibrates (too low) and so on. You learn it.

 

Anyways, on our Lycoming with 140 PS we removed old soot and oil from the valve seats by giving it full throttle and leaning it out. This can get the exhaust manifold glowing hot, but you feel it. 

Sure, butt feeling is lacking completely. There's still sth strange about it. I tested the Yak lately at summer setting, 2km in level flight with constant max throttle, full open radiator and varying mixture settings to spot differences in airspeed, engine temperatures ect. The impact leaning the mixture had was nearly insignificant between 85 and 100% and engine temperatur was constant. Than going lower to 70% the engine temperature started rasing like 0.5°C / min and speed droped to ~30km/h less than 100%.

 

The very low temperature gain despite leaning mix to 2/3 seems questionable to me.

Edited January 17, 2016 by Stab/JG26_5tuka

[Jizzo]

That explains the difference. Still question remains how russian pilots managed to set their mixture accordingly. I doubt they stacked their heads out looking for exhaust flame colours.

That's exactly what i was wondering, how we should be able to do it now.

 

Because as the new head limitation system got introduced you can't see the flames midflight anymore.

 

So on my earlier question i thought you found something out.

 

I noticed on the yak-1 the RPM's start to oscilate during your way up to 4000m already and as i recall someone saying that on the yak-1 mechanics setup the plane that it could run fully Rich mixture from 0-4000m only by adjusting the supercharger at 2300m to stage 2 and from 4000m up you had to start adjusting as RPM's start to oscilate.

 

So i'm curious, if there is something wrong ingame?

Edited January 18, 2016 by Jizzo

[Finkeren]

That explains the difference. Still question remains how russian pilots managed to set their mixture accordingly. I doubt they stacked their heads out looking for exhaust flame colours.

Most of the time they wouldn't have had to touch mixture at all.

 

The two-speed superchargers on most Klimov and Shvetzov engines can keep up with the falling air pressure up to around 4000m. Above that altitude however you definately see the effects of incorrectly set mixture.

 

With the Mikunin engines it's very different because the engines functions differently, and mixture settings directly influenced manifold pressure.

[mb339pan]

mixture sistem work wery well on P40, the difference between poor and rich mixture is having serious repercussions on engine performance, rpm fall if the mixture is too rich or too poor

Edited January 18, 2016 by 150GCT_Pan

[Finkeren]

mixture sistem work wery well on P40, the difference between poor and rich mixture is having serious repercussions on engine performance, rpm fall if the mixture is too rich or too poor

The mixture system works very well on all the planes, at least the ones where it's manually controlled.

[SC_Manu653]

This is how I use mixture. Like on a Cessna, I lean the mixture until the RPM begin to drop, and I slightly enrich it to keep it a the RPM just before he dropped. Not sure if it's the best way but it works well for me.

[6./ZG26_5tuka]

Yes, but that only works for planes with fixed pitch propellors (like in RoF). In aircraft with constant speed propellors a too rich mixture is indicated by MP drop.

 

Thats the theory at least. Still don't know why it doesn't apply to the Yak and Lagg (at least under second gear switch altitude).

Edited January 18, 2016 by Stab/JG26_5tuka

[SC_Manu653]

Don't know either, but it works well for the Lagg and the Yak too. Leaning first and enrich it after the drop of RPM.

Edited January 18, 2016 by 4./JG53Manu653

[6./ZG26_5tuka]

Not so much according to my tests. Optimal performence mix for the Yak seems pretty much 100% at 2km (probably slightly lower above). Lowering the mix from that does have impact on performence and (to a very small extent) cooling efficiency, MP and RPM remain constant however (not talking about the small RPM geeks right when changing the mixture as thats only a swift change).

Edited January 18, 2016 by Stab/JG26_5tuka

[SC_Manu653]

You are right 5tuka, under 2km, if I do this I will have overheating issue faster. You need to lean it nearly at 50-55% to get the drop in rpm and overheat your engine for nothing.

[JtD]

Yes, but that only works for planes with fixed pitch propellors (like in RoF). In aircraft with constant speed propellors a too rich mixture is indicated by MP drop.

 

Thats the theory at least. Still don't know why it doesn't apply to the Yak and Lagg (at least under second gear switch altitude).

Manifold pressure does not go down unless rpm go down, because rpm drive the supercharger directly. If outside air pressure and supercharger rpm remain the same, manifold pressure will do as well. Unless you close the throttle.

 

On most aircraft of WW2 you were supposed to use mixture:

a) according to the book which gave specific instruction

b) according to the exhaust flames

c) according to the exhaust temperature (some planes had gauges for this)

d) according to the engine temperature.

A Yak-3 manual for instance references the exhaust flames for guidance.

Edited January 18, 2016 by JtD