In the patch notes it was said that the boost gauges aren't displaying the correct values.
Maybe you overboosted without realizing it.

Yes, doesn't sound like you were abusing the engine. Perhaps the cooling model is at fault and the engine is simply running hotter than it would in reality at the climb power setting. In the game it only seems to take a few seconds of over temp to screw the engine up.

Perhaps next time you try it you could watch the oil and water temps carefully and record any excessive temps that occur during the climb. A recorded track would be even better.

Cheers

"I've also learned that it should'nt be the case since they are normally auto rich and auto lean so lean shall work better in theory."

Not really Auto lean is really only of use for cruising and has Max boost limitations associated with its use.

Currently in game if run Boost cut out you need to push the mixture lever forward to AUTO lean to get smooth engine operation. This is of course totally wrong and should result in engine issues pretty darn quick.

SPIT MKII Boost limitation in Auto lean is +4/2650 100 Octane or 2.25/2650 at 87 Octane.

Spit MKI Boost Limitation in Auto Lean is +2.25/2600 87 Octane.

Unless you are really interested in best fuel consumption then Auto Rich is all you should really need.

Yes but apparently ok on Hurricane, anyway the boost is part of a factory setting and I don't think one can over boost unles using the boost cutout.

Up to 6 1/4 (6,25) it's the rated (the gate). Should be allowed continuously except that it may impact on the engine's lifetime, thought I don't think it should fail during the flight really.
That is at < 2850 rpm.

Nevertheless I usually fly at lower rpm. Surely enough speed and rad fully opened + temeprature checks should be done, but when I failed the engine, I do not recall it was too warm.

I really think the real aircraft handles its nominal climb boost and revs up to the top, that is 2850 rpm 6 1/4 boost up to 30'000 ft, and we're still far from that.

Should be cross checked, but in my mind, it should handle that.

But I really think that's side effects from inadvertant engine and flight model changes. They are not documented anywhere that I know and one has to try to see what is working and what is not.
I used to read the historical manual, but what you find does'nt essentially apply to CoD.

I am indeed. When we do fly some historical battels, most of us are falling down due to lack of fuel or lack of lifting surfaces ;) generally.

AFAIK jf, the Merlin can handle 6.25 lbs/3000rpm only for 30 mins, before issues occur. However, as it is now, you are lucky if you can go 2800rpms without cooking your engine and that is in level flight.

Ive found if you apply a bit of common sense and watch your temperatures you can get by. Ive run with boostcut and water temp up to 120c and oil to 97c for about a couple minutes without failure but water needs to be mostly under 110c and oil 95c to avoid damage. With temps properly managed I have run boostcut continuously for 30mins without any noticeable damage.

Though I am not really into in-depth-knowledge of engine limitations, I do agree that current performances are a bit shaky at best.
Before the current beta patch my guideline was "2600rpm with full boost (sans c/o) for continuous operation" (*) for both the SpitMkIa100oct and the Hurri100oct. But now, even that is no more guarantee... you really seem to be forced to tone it down to about 2400-2500rpm in order to maintain reasonable oil/cooling temperatures.

(*) The spit Mk I manual even says that somewhere, if I remember correctly - but the other limits, like the cut-out limit of 5 min. or the rpm limit of 3000 for i-dont-remember-how-long-exactly were always way off imo.

Actually, even with semi automatic mixture it's advised to use auto-rich whenever using high power settings. That depends on the aircraft and doesn't only mean WEP/boost cut out. It could also mean any boost above +5.

I don't know what the real aircraft used and how it's modeled in the sim, but from flying various A2A add-ons on a friends's FSX installation and after reading various manuals of real aircraft, it's pretty clear that high power needs rich mixture.

I think it's because it helps cool the engine and prevents detonation. I think detonation is improper fuel burning through pre-ingition, which damages the piston rods because they are out of alignment at the time of ignition, but i'm not entirely sure.

Generally speaking and as a safety measure, only use auto-lean for cruise. Cruise means the specified engine settings, not simply flying straight and level at whatever boost we want, it could be as low as +1 boost. Take-off, climb and combat should be done on rich, as well as fast cruise.

I don't know the limits for the Merlin (Spits and Hurris) but just as an example, let me give you the Mercury engine limits from the Blenheim pilot's handbook. The engine can do +5 at full throttle and +9 with the boost cut-out activated.

Nevertheless, anything above +1.5 requires auto-rich:
economy cruise is +1.5 at auto-lean
fast cruise is +3.5 at auto-rich.

In other words, just because there is spare power it doesn't mean it's sustainable at all times and conditions. That being said, i agree that some of the in-game limits are currently off the mark.