Engine blows for no apparent reason.

I've been practising dog-fighting in the P-51 and the engine is popping for reasons I don't understand.

I've attached a couple of tracks to show the behaviour. The mission is default weather, no random failures etc. In each track I'm not trying to shoot the enemy down, my aim was to record how long the engine lasted under dogfight conditions.

In Track 1 I set the RPM to 2500 and the MAP averages 50 and never goes over 55. The engine lasts all of 2:35.

In Track 2 I red line it with a constant 3000 RPM and 61 MAP. The engine goes well past 20 minutes before popping.

Why is the engine dying under presumably less stress?.

p-51 engine shutdown 2min35.trk

p-51 engine shutdown 20mins.trk

P-51D 1v1 FW-190D.miz

Unfortunately I can't open the tracks right now. But it's possible that you overheated? Even at low settings, if you climb too much or hang on the prop, it would lead to overheating. I can't open the track right now, but because you didn't mention it, I'm just asking if it's a possibility.

Also, 50MAP at 2500RPMs seems a bit troubling. You don't want such high MAP with that low of an RPM setting. That would be stressful.

Temps are fine (according to the instruments) and the radiators are on automatic in both tracks.

edit: this was 1 second before the engine blew...

I can't think of anything. I have to work to overheat my Mustang. But you said you're not overheating. I'm quite puzzled. I can't look at the tracks though, so I can't really say much more.

I've got nothing.

A tip for the future, post which version of the game was used to record tracks, so that we know in which one we can play them (though given poor reliability of tracks playback, we probably won't do it successfully anyway).

As for the first scenario - a couple of patches ago, pre-ignition/detonation has been finally implemented in DCS warbirds engine simulation. As a result, flying with high MAP and low RPM is a no-no, just like in real planes. Obviously, at lowest RPM one cannot get highest MAP out of mechanical supercharger anyway, but at certain higher RPM boost jumps up enough for the pre-ignition to begin. In both DCS Merlin engines it's somewhere about 50-ish @ 2500 and it kills engine quickly, so I'm pretty sure that's what happened to you .There's an audible bass rumble before the engine dies, so if you listen carefully, you can still save yourself if you react quickly.

As for the second scenario, my guess is "normal" overheating :D. You really need to watch your speed and temps when dogfighting with combat power parameters.

Yeah, should've said 1.5.7.

Thanks for the info on the pre-ig/det - and I thought I was being gentle on the engine!

Ha! 50" is takeoff setting for lightly loaded plane, while 2500 RPM (normally at 25" :) ) is for econo cruise. That's as far from gentle combination as one can get :D

A tip for the future, post which version of the game was used to record tracks, so that we know in which one we can play them (though given poor reliability of tracks playback, we probably won't do it successfully anyway).

 

As for the first scenario - a couple of patches ago, pre-ignition/detonation has been finally implemented in DCS warbirds engine simulation. As a result, flying with high MAP and low RPM is a no-no, just like in real planes. Obviously, at lowest RPM one cannot get highest MAP out of mechanical supercharger anyway, but at certain higher RPM boost jumps up enough for the pre-ignition to begin. In both DCS Merlin engines it's somewhere about 50-ish @ 2500 and it kills engine quickly, so I'm pretty sure that's what happened to you .There's an audible bass rumble before the engine dies, so if you listen carefully, you can still save yourself if you react quickly.

 

As for the second scenario, my guess is "normal" overheating :D. You really need to watch your speed and temps when dogfighting with combat power parameters.

When you are stressing the engine at all, you must manually open the radiator flaps (for at least 20 second after which they will remain open). I have a button on my throttle for that purpose and use it frequently.

The lower the RPM the longer you're subjecting the connecting rod to pressure. I recommend always keep the plane at 3000 unless you're cruising... then reduce pressure FIRST and then reduce RPM so both are in the green section of the dials. Upon needing more power again... increase RPM FIRST then increase pressure taking care to not let that over rev the engine.

All good advice, thanks chaps.

You need to watch engine temp like a hawk in this aircraft guys, it's part of your scan. Do you guys know what that is? If I were your flight instructor I'd be constantly harping on you. Engine temperature and pressure parameters will prevent blown motors. Please adhere to this rule and SCAN constantly.

I've been told that the real P-51D was a lot more tolerant of high temperatures than it is in DCS. I haven't read up into it at all however. You guys have any input on that? I thought the engine was pretty accurate (as can be in a sim, for the first WWII aircraft in it).

While at it, it came to my attention some time ago that the Mustang had a release valve for the coolant, if it got too hot, and the pressure built up too much. It was built into the airframe, by what I've been told. I don't know what that means but that's what the guys said. This is off of memory from months ago, but I brought it up in the P-51 group on Facebook, and it's a thing. They told me some stuff about it, but it was a while ago.

ED would probably want actual documentation, but still. What other Merlin dynamics are we missing in DCS? :/

You need to watch engine temp like a hawk in this aircraft guys, it's part of your scan. Do you guys know what that is? If I were your flight instructor I'd be constantly harping on you. Engine temperature and pressure parameters will prevent blown motors. Please adhere to this rule and SCAN constantly.

At least based on the screen shot above he didn't blow it because of temps... It's because he was running 2400RPM and 50 an the MAP. That'll do it :).