Spitfire oil pressure always high and weird starter stuck

[-0303-]

Multiplayer, so no meaningful track. Don't know how to recreate so therefore not a bug report.

 

1) Oil pressure

Generally oil pressure is at 120 psi or over unless boost & rpm set low. Recommended is 60-120. I find it a bit off that oil press is almost always at 120 or more. Specific case now. Flew 100 nm abouts. Boost 7, rpm 2850. I noted how the oil pressure was stuck at upper range (150). Why? Wasn't stressing engine at all. -3'C degree Aerobatics Online Server. Landed, engine quit. Figure it was the high oil press was the cause.

 

I've noted typically oil pressure drops with radiator closed (switch forward off). Flipping switch rearwards (radiator auto, opening), oil pressure always goes up even more.

 

2) I long noted occasional weirdness with the starter. Specifically sometimes it refuses to turn over after repair and adding ground power does nothing.

 

Brand new weirdness (same flight as above). Attempting to start after engine quit, it didn't, as expected, assuming engine seized. But, further, volt meter dropped and stayed dropped after releasing starter button. Then I could watch the voltage dropping as if something (starter engine?) just drew tons of current.

Immediately after repair finished, prop turned over as if starter engine was still stuck. Watching the voltmeter I clicked the starter button and prop stopped turning and voltage shot up a bit again (as if "unsticking" the starter button).

 

Attempting to start to start after repair. Voltmeter at 10V (which I remember is to low, needs 13-15V). Prop turns over slowly. Add ground power and once again confirm ground power does not work. With ground power, obviously prop should spin over fast enough to start. I even believe starting by battery was the exception in real  life. Add a link to my old thread when I find it.

One thread (commented but not started by me) on no working ground power.

I observed some weird volt flickering, which i note is commented on in linked thread also.

Edited March 4, 2021 by -0303-

[-0303-]

Found (and bumped just becos ...) my old bug report on "Connecting Ground Power will not turn over engine with drained battery". This linked bug report is specific, well defined, one year old without ED input, an unambiguous bug unlike my unspecific meandering above ...

Edited March 4, 2021 by -0303-

[grafspee]

Spitfire has not implemented real Cooling model, which consists  thermostatic valves on oil and coolant radiators, which prevents over cooling, at low power settings or at high speeds, oil and coolant temp may go below operating temperatures and this directly influencing oil pressure. If you would cruise at 2500rpm at 4lbs boost  at  -10C SL temp your oil temp would pretty much go near 0 C.

As you noticed already, spitfire's cooling doors have 2 positions closed=normal operation and wide open=when coolant temps exceeds 130C. This is complete different case then in P-51 where cooling doors will adjust position to maintain set temps.

In spitfire only mean to manage temps are those thermostatic valves which are now wide open all the time.

Solution for this in cold temps if just run engine at least at 2850 and 12lbs of boost

Edited March 4, 2021 by grafspee

[Art-J]

-303- just to emphasise one thing which Graf mentioned above, although indirectly - you've got switch position mixed up. It's the other way around:

- Forward = auto (and thus usually doors are closed until you start overheating);

- Rearwards = manual, and it has only one emergency setting - doors full open. If you keep flying that way in cold conditions (even if we forget about thermostatic issue), you're most likely have the engine overcooled often, thus oil temp below recommended limit and oil pressure above it.

Edited March 4, 2021 by Art-J

[-0303-]

Quote

not implemented real Cooling model

 

Explains ... a lot. Assuming it's coming.

 

Quote

got switch position mixed up.

Ok, I was uncertain. Anyway I had, and have, it forward 90% of the time to keep oil pressure down. I only flip the switch rearwards when it's obviously overheating.

Edited March 4, 2021 by -0303-

[-0303-]

3 hours ago, grafspee said:

As you noticed already, spitfire's cooling doors have 2 positions closed=normal operation and wide open=when coolant temps exceeds 130C.

You wrote 115 before editing to 130? DCS manual states:

Quote

Control of the radiator grates is automatic depending on the coolant temperature. The grates open at temperatures above 115°C. In case of system failure, the grates may be opened by pressing the button located on the left side of the pilot seat.

and also

Quote

Do not allow an increase in coolant temperature beyond 120°C and oil temperature beyond 85°C.

so 130 would be way to late.

Edited March 4, 2021 by -0303-

[grafspee]

Yes they open at 115C. The main point was that radiators can open or close nothing between.

[-0303-]

Didn't know the radiator On/Off nature. Always assumed it was gradual. But reading "Pilot's notes" it never says "gradual", it just says "open at 115C".

[grafspee]

10 minutes ago, -0303- said:

Didn't know the radiator On/Off nature. Always assumed it was gradual. But reading "Pilot's notes" it never says "gradual", it just says "open at 115C".

Exactly, they open fully only when coolant temp is at critical level, temp regulation is done vie thermostatic valves, which will regulate how much of oil/coolant is directed to radiators.

I think that radiators with closed shutters, provide the lowest drag possible.

Higher end of temps will act the same way no matter if valves are simulated or not, since those would be wide open anyway.

The difference shows up at lower temps = low power setting, fast flight, high alt cruise, cold conditions. When coolant/oil temps drop to 80C thermostatic valves will cut off flow in to radiators completely. So coolant and oil will circulate only with in engine, for example when you will reduce power to 0 even at cold conditions coolant and oil should not drop below 80C.

In DCS case valves aren't there, so full oil/coolant flow goes through radiators quickly reducing temps way below minimal level.  

Edited March 4, 2021 by grafspee

[-0303-]

Always love learning about the airplane systems. Spitfire cooling is both more complex and simple than I thought. Design makes sense, keep max low drag until absolutely necessary. Control temp by redirecting cooling fluid to the radiator and only open the flap at 115'C.

 

So Spitfire cooling modeling is incomplete with the result that one cannot do what I did. Cruise long distance in cold weather on low power without destroying the engine.

 

Is this on a list for "fixing"?

Edited March 6, 2021 by -0303-

[Art-J]

Well, we've read a few times lately that inline engined planes are going to have a general  overhaul of cooling system modelling in unspecified future, but that's all we know.

 

Just like all things DCS, it's done when it's done.

Edited March 6, 2021 by Art-J

[Nealius]

Revisiting. Is there a definitive issue with high oil pressure? On Normandy, 10C mission temp, oil pressure is pegged at 150+ from engine start. It doesn't appear to affect the engine at all, but I periodically dilute the oil down to 120. Oil pressure will go back to 150 within two minutes or so. Oil temp around the 1~2 o'clock position. Rad temp at 60 or a smidge more...getting a bit overcooled at 2850/+4 to maintain formation with AI in campaigns.