Engine settings for max fuel economy

[RedKestrel]

Whenever I'm reading up on engine management for soviet fighters, it seems that the recommendations are to keep engine RPM at maximum and just adjust the throttle to change power output. I'm sure this works out well for short missions and everything, but I can't help but wonder about the impact on fuel consumption on longer flights. In their pilots notes american and british fighters have recommended settings for 'economy cruise', but I can't find that information for Soviet fighters anywhere in English.

What I've been doing to get max economy is setting mixture as low as I can to get the blue flames in the exhaust, and watching the MP gauge for any drops below a certain point. Then I'll lower my RPM and throttle settings a bit and try and hit the cruise speed recommended in the career missions. It would be nice to know if there are recommended or best practice settings for fuel economy, or general principles. WIth some of the longer missions in the I-16 late in the Moscow campaign fuel consumption is a real concern.

As a bit of an aside, I don't think the AI is very good at managing fuel consumption, as during one escort mission my entire squad declared 'bingo fuel' before we hit the target, leaving me to drive off the fighters attacking our bombers alone. Some of the campaign missions take place at the extreme edge of the I-16's effective range and don't leave much left over for combat. 

[ZachariasX]

The Napier Sabre is the only engine in a fighter that runs at very high revs while still producing good mileage. This for the simple reason that (in contrast to ALL engines we have in the game) it was very high geared and like that (at high rpm and refuced manifold pressure) you could obtain cruise speeds almost as high as the top speed.

 

All other engines (in the real world) should be kept at reduced rpm (and Manifold) to allow leaning out the mixture.

 

In the game, you can be pretty drastic with leaning the mixture. It takes a great lot to suffer consequences, so you can game the game like that.

[Hipsu]

I just started a Moscow career in a I-16 and also noticed that during bomber escort missions the entire AI squadron yells bingo fuel way before we reach the destination... not good.

 

I'm also interested in learning the proper escort speed economy settings for the I-16 (and other Russian planes). When it comes to CEM I don't really know what I'm doing. I know to lean the mixture all the way down to blue flames, but what about the RPM and throttle?

 

The nominal settings (2200 RPM at 915 ATA) are about 90% RPM at full throttle. If I want to fly slower and also save fuel AND be nice to the engine, which is better: low ATA (throttle?) at high RPM? Or low RPM but high ATA? I suspect the answer is to reduce both, but basically which one should be "higher" than the other?

Edited November 11, 2019 by Hipsu

[CountZero]

You can go in quick mission and set airplane in air with 10% fuel and start leve autopilot on go on max power and see when fuel run out, (you can use time accelaration so you dont wait full 4-9min depending on airplane).

 

Then run more tests like that to see with what lower settings of power, or mix or rpm you get best extended time on what you got with max power, sometimes you can triple the time. 

[ZachariasX]

4 hours ago, Hipsu said:

low ATA (throttle?) at high RPM? Or low RPM but high ATA?

Just look at the way your car is doing it (in case it is fairly modern and has some sort of automatic transmission).

 

The best source for maximum mileage are the pilots notes. It states most efficiant settings.

 

Generally, you go low rpm, lean mixture, high torque ("ata"). Merlins run well at 1800 rpm and so do most other such engines. How exactly you do it depends on your actual scenario. Milking the last mile from your AC is almost an art.

 

So, for the Mustang for instance, cruise is anything between 43'' @ 2500 rpm to 30'' @ 1800 rpm. Weak mixture is below 36'' @2400 rpm. You want the automatic system to enter a renge where is uses a weak/lean mixture. The slower you go, the longer you will fly. How far you will go, that depends on your weight as much as the wind. Range s always best if unnecessary parasitic load is removed from the crankshaft, meaning you would want low supercharger gear, if that still keeps you within your desired cruise settings. This as a real world example.

 

In the game, you can be more drastic. First, one thing to consider is that at 1500 rpm, there is about half the fuel flow than at 3000 rpm at the same "ata" rating. So, as a first step, decrease rpm, maybe down to 2000 rpm. See MAP dropping accordingly. The engine should still be running ok and you will need some 35'' to 45''  (~1.1 ata) MAP to keep going. Set your throttle accordingly. Notice the aircraft getting slower. If your airspeed gets too low, try to increase throttle. If you are already full forward but you require more speed, up the rpm. As soon as it reached a speed that you still deem ok, start leaning out the mixture (if you can). As you starve the engine for fuel, this does not show on the MAP gauge, but it comes as a net decrease of airspeed. What you will do is slowly lean out the mixture until you notice the aircraft getting slower. Don't lean it past that point. Check oil and water temp regularly.

 

 

[RedKestrel]

5 hours ago, Hipsu said:

I just started a Moscow career in a I-16 and also noticed that during bomber escort missions the entire AI squadron yells bingo fuel way before we reach the destination... not good.

 

I'm also interested in learning the proper escort speed economy settings for the I-16 (and other Russian planes). When it comes to CEM I don't really know what I'm doing. I know to lean the mixture all the way down to blue flames, but what about the RPM and throttle?

 

The nominal settings (2200 RPM at 915 ATA) are about 90% RPM at full throttle. If I want to fly slower and also save fuel AND be nice to the engine, which is better: low ATA (throttle?) at high RPM? Or low RPM but high ATA? I suspect the answer is to reduce both, but basically which one should be "higher" than the other?

The AI I-16s always seem to run at auto mixture, which is a slightly rich mixture. Auto mixture for the I-16 is set to 100%.

The I-16 has really 'short legs' as a fighter, even compared to other Soviet fighters.  The AI doesn't seem to be able to manage the fuel properly to fly all the way through the longer missions, and even in your own plane you will be hard pressed on some of the longer missions - you can't just rely on the auto mixture to get you there, you have to lean and use reduced throttle settings. When I flew career in I-16 I set up to keep pace with the bombers, set my RPM and throttle as low as I could to match speed with the bombers, adjusted mixture until I saw blue flames, and then adjusted throttle a bit to keep pace with the bombers. That was the only way I could stick with them for the whole mission, and when you get into combat be aware that you really will probably only have a few minutes at combat settings to get your licks in before you have to disengage.