correct as-is Unusual Oil Pressure Activity (vid and track included)

[Magic Zach]

Since the update to the radial engines in DCS, I noticed an odd behavior with the oil pressure in the Anton.  The pressure while warming up (1100 and 1500RPM result in the same oil pressure) is high at 15 kg/cm².  What is odd is that right when the oil temperature reaches 45C, the oil pressure will immediately drop to roughly 8 kg/cm².  I would normally expect oil pressure to gradually decrease as oil temperature increases, not instantly drop right at 45C.
I have a link to a video on Google Drive, showing the moment of the pressure drop here.
Additionally here is the track during of the time of this video here.  It's from the Storm of War server, but seeing as warmup only occurs on the ground, the track doesn't have an opportunity to lose its accuracy and kill me before you should see the oil pressure behavior yourself.

[grafspee]

This oil pressure behavior in fw190 is like that since release.

Edited December 30, 2020 by grafspee

[71st_AH Rob]

To close the loop and for historical record:

 

There may be a bug with the oil pressure in the A8, however the overall behavior as described is not unexpected.  For example in my classic car the way you can tell the engine is warm enough is when the oil pressure suddenly drops to the normal zone, which is coincidentally just before the temperature enters the normal operation zone. The the oil pressure jumps to 60 psi on start up and gradually begins to drop when the temp begins to rise. As the temp approaches 70c it will suddenly drop to 35c or so from about 50c.

 

Engine oils today are different from oils produced in the 1940's.  Oils produced then were what we call today mono-grade as opposed to modern multi-grade oils like 10W-30.  Modern multi-grade oils provide protection at a wide range of temperatures older oils provided protection at a much narrower band of temperatures. Older mono-grade oils tend to be 'thicker' at room temperature and are not providing protection to the engine when cold so warming up is more important, the oil will suddenly become more fluid as temperature approaches the range it was designed to operate at.  Modern multi-grade oils are fluid at room temperature and provide protection at start up as well as at the designed operating temperature so warming up your car, except in the coldest conditions is not as much of a requirement.

 

The original owners manual for my classic recommends Castrol XL or Mobiloil Special etc as the replacement oil, which was likely 40 or 50 SAE, today I use 20W-50 which provides greater protection at start up but still wait for it to reach operating temp before driving it.  The manual goes on to state ' the minimum pressure at 3,000 r.p.m. when hot should not be less than 40p.s.i.'  Normally at idle it is 35 and increases as engine load increases.  I would expect an aircraft engine to behave similarly.

[grafspee]

44 minutes ago, 71st_AH Rob said:

To close the loop and for historical record:

 

There may be a bug with the oil pressure in the A8, however the overall behavior as described is not unexpected.  For example in my classic car the way you can tell the engine is warm enough is when the oil pressure suddenly drops to the normal zone, which is coincidentally just before the temperature enters the normal operation zone. The the oil pressure jumps to 60 psi on start up and gradually begins to drop when the temp begins to rise. As the temp approaches 70c it will suddenly drop to 35c or so from about 50c.

 

Engine oils today are different from oils produced in the 1940's.  Oils produced then were what we call today mono-grade as opposed to modern multi-grade oils like 10W-30.  Modern multi-grade oils provide protection at a wide range of temperatures older oils provided protection at a much narrower band of temperatures. Older mono-grade oils tend to be 'thicker' at room temperature and are not providing protection to the engine when cold so warming up is more important, the oil will suddenly become more fluid as temperature approaches the range it was designed to operate at.  Modern multi-grade oils are fluid at room temperature and provide protection at start up as well as at the designed operating temperature so warming up your car, except in the coldest conditions is not as much of a requirement.

 

The original owners manual for my classic recommends Castrol XL or Mobiloil Special etc as the replacement oil, which was likely 40 or 50 SAE, today I use 20W-50 which provides greater protection at start up but still wait for it to reach operating temp before driving it.  The manual goes on to state ' the minimum pressure at 3,000 r.p.m. when hot should not be less than 40p.s.i.'  Normally at idle it is 35 and increases as engine load increases.  I would expect an aircraft engine to behave similarly.

Unless you have thermostatic oil pressure regulator which will increase oil pressure for low temps, once desired oil temp is reached regulator will switch to normal oil pressure.

It is obvious that this oil pressure behavior is not simple solution like it is done in car's engines.

higher oil pressure in automobile's engines when engine is cold is done by design, diameter of the pressure regulator is set to specific value, that when engine is cold oil pump will provide increased oil pressure. This is why you see gradual oil pressure drop during warm up. If pressure regulator would be twice the size you would not see this, oil pressure would be low even at low temps, but engines bearing would be dead quickly at very high viscosity and very low oil pressure there would be almost non oil getting in to bearings.

Once main pressure regulator kick in in fw190 oil pressure remains steady no matter the rpm, so regulator diameter is large enough to dump any excessive pressure no matter the rpm, unlike in car when  you increase rpm oil pressure will increase as well, even when engine is warmed up, so fw190 need second regulator for warm up.

another thing whne engine is warmed up in fw190 and your rpm will drop below certain value main oil pressure regulator is cut out and auxilary regulator kicks in increasing oil pressure, this system protect engine from low oil pressure. Complete different oil system then in automotive engines.

Edited December 30, 2020 by grafspee