Is the Mixture broken?
 

It seems at least in the 109 and the Spit they only have 2 settings either full rich or full lean. I have assigned buttons to increase and decrease mixture but I only get those 2 choices. The Mixture on the Hurricane works fine and can be adjusted in increments(other than its backwards to the other 2 planes)

Yes the mixture is broken.

For the British planes, there should be only two positions, the Hurricane is wrong.

For all planes, the carburetors and fuel injection systems were designed to lean the mixture as the aircraft gained altitude. This is not modelled properly, hence the stumbling and backfires at higher alts.

I give you a hint without spoiling, as part of the fun I think is researching the planes. The mix on the 109, it's not what you think. Good luck.;)

Or it's something similar to the soundbug, were we hear wheels moving when plane is standing still or even retracted and in air.
Could it be that carburators act like plane is always bumping around on ground?
But I also suspect something wrong with oil temperature on planes without oil radiator control.
Like Hurricane oil temperature going very fast up to 90+ and staying high, even without realistic engine control.

Yes, I agree with you Buzpilot.

The only thing that's not broken is that it's a 2 position lever in RAF planes. it's either "normal" or "weak" - this latter one is for cruising at high alts, nothing more.

It seems that our mixture is not adjsuted automatically at higher alts.

Also, oil temperatures appear to be broken too. I can't get them below 80, and they usually end up going above 90 and killing my engine. (Spit)

I'm glad we have this very complex CEM, should be even more complex with primer pumps and stuff, BUT broken and bugged as it is, it's just a pain in the arse.

Actually it's more complicated than that.

Auto leaning does work, but not on all aeroplanes.

If you take the Tiger Moth for a flight, and have plenty of time on your hands, you can climb it above the altitudes at which the fighters start to suffer backfires and suffer no ill effects. If you fly in no cockpit mode then you can look at the exhaust flames and see that they stay blue.

Also, I tried moving the mixture control in the Tiger Moth and it appeared to be locked in the rich position.

Make of it what you will, but I think that either there has been a mix-up, such that the Tiger Moth has ended up with an automatic mixture control that a fighter should have, and the fighters have ended up with something weird, or else the actual culprit is the supercharger.

Obviously I don't know how the model is coded. However, if they were trying for really high fidelity then a real SU carburettor has two needles, one controlled by ambient pressure and the other controlled by supercharger boost pressure. The second needle therefore enriches the mixture to protect against detonation at high boost pressures, whilst the first needle provides the basic fuel demands of the engine and also provides altitude compensation.

It seems to me that what's happening is that the model is enriching the mixture as a function of the ratio*:

P[intakemanifold]/P[ambient]

This means that we're getting boost compensation in the correct sense, but no altitude compensation. What should actually happen is that we should have

Needle 1
Spring acting to close needle, vs atmospheric pressure acting to open it

Needle 2
Spring acting to close needle, vs boost pressure acting to open it

*NB - this ratio is not the supercharger pressure ratio. To a first order, the supercharger pressure ratio is a simple function of rpm because the throttle is upstream of the supercharger. The second order correction is that its running line is also going to be affected by exhaust back pressure. For this reason I'm not entirely convinced by the boost increase with rpm reduction that we see, because supercharger pressure ratio varies as rpm^2, whilst engine air consumption varies roughly as rpm^1. But that's another debate.

Viper, the Moth has interlocked mixture & throttle. i.e. you can't lean your mixture further than you decrease the throttle. "semi-automatic" if you like :)

however, Merlin aircrafts are definitely broken.

I certainly agree that something is wrong with all the fighters (even the fuel injected German ones); but it's not obvious exactly what is causing the backfires. Mixture problems are implied by the flame colour, but the fact that the Moth doesn't suffer implies that the supercharger may be to blame, since that's the one difference between the Gypsy III/Gypsy Major and the afflicted engines.

Before the latest patch the mix on spit (back rich) worked ok, switching to lean mix for cruising worked ok till you got above about 16000 then it all went tits upwards , running too rich spluttering vibrating etc.
Now since the last patch I really dont know what the hell is happening with the mix. Taking off I get better acceleration with lean (fwds) mix ?? Before the patch the engine wouldnt even start with wrong mix selected, this is how it should be. Now the engine will start with any mix selected. Rich mix just doesnt seem to be any use , but still at +16000 the mix is far to rich.
I can only speak about the spit, so far I have concentrated on one type of aircraft and will learn the others given time.However this mixture problem seems to be across all aircraft judging by the forum posts, It seems to me to be at the heart of many engine problems people are suffering in this game especially when going for alltitude.