Engine running too cool LOP?

[Little Dipper]

Question for the engine guru's.     Unless I am in a hurry I've been operating my new 310 hp IO-55O lean of peak.  When I am flying LOP in cold air I can't keep my cylinder temps above 225  or my oil temperature above 150.  If I run ROP my temps return to normal.    My question is does it do long term harm the engine to run it LOP when the engine operating temp are that cool?  

Norm

N995K

[Brandt]

13 minutes ago, Little Dipper said:

Question for the engine guru's.     Unless I am in a hurry I've been operating my new 310 hp IO-55O lean of peak.  When I am flying LOP in cold air I can't keep my cylinder temps above 225  or my oil temperature above 150.  If I run ROP my temps return to normal.    My question is does it do long term harm the engine to run it LOP when the engine operating temp are that cool?  

Norm

N995K

Based  on what I’ve read, would seem the two issues are water vapor in the oil that doesn’t boil off, encouraging corrosion and lead deposits in the cylinders because the chts aren’t high enough to burn them off. 

[PeteMc]

Not a mechanic... but in talking to some about LOP in general...

There are LOTS of internal engine components that are plenty hot enough to get rid of any moisture if the plane is flow regularly.  (Or will get rid of it if that particular flight is pretty long to allow for the moisture to be eliminated. 

And there is less lead due to the reduced fuel flow and a better burn LOP, so led deposits should not be an issue.  Best way to confirm this is to look at the dark plugs with buildup from a plane that runs ROP and the very clean lighter plugs from a plane that is run LOP (especially if leaned aggressively on the ground).

 

[LANCECASPER]

45 minutes ago, Little Dipper said:

Question for the engine guru's.     Unless I am in a hurry I've been operating my new 310 hp IO-55O lean of peak.  When I am flying LOP in cold air I can't keep my cylinder temps above 225  or my oil temperature above 150.  If I run ROP my temps return to normal.    My question is does it do long term harm the engine to run it LOP when the engine operating temp are that cool?  

Norm

N995K

There is a cold temperature kit that Mooney makes to slide over and partially block the oil cooler on Ovations to keep the temps up in cold weather.

[Shadrach]

Need more info. “Running LOP” is not a lot of information to go on.

What power setting?

How far LOP? 

I run LOP almost exclusively this time of year because the dense air makes for near SL power into the cruise altitudes (I often see DAs of -3000ft or lower at my 700ft field).  However, LOP means 5° to 15° not 50°. I use CHT as proxy for cylinder pressure but he noumber must change with OAT. A power setting that yields a CHT of 370° in August (acceptable detonation margin) is much different than the power setting that yields a CHT of 370° in February (quite a bit less detonation margin).

Your problem is at the other end of the spectrum and it may be that you’re running way more conservative than necessary. Is it a problem, likely not in the short term. Longer term you may have problems with lead scavenging (fouled plugs) and high moisture content in the oil. The latter can be solved with the cold weather kit Lance mentions above. I use the cheap and cheerful method of blocking the oil cooler with aluminum tape. Not necessarily because I am cheap (guilty) but because of the 40° swings in OAT. It’s not unusual to see 60° and 14° in the same week during daylight hours. I like having the option to block, partially bock or completely block the oil cooler in just a few seconds. 
I adjust cooler winterizing to facilitate cruise oil temps between 185 and 210°.

[StevenL757]

3 hours ago, Little Dipper said:

Question for the engine guru's.     Unless I am in a hurry I've been operating my new 310 hp IO-55O lean of peak.  When I am flying LOP in cold air I can't keep my cylinder temps above 225  or my oil temperature above 150.  If I run ROP my temps return to normal.    My question is does it do long term harm the engine to run it LOP when the engine operating temp are that cool?  

Norm

N995K

Norm, the kit that Lance @LANCECASPER shows above is a necessity for us in the NE, so not sure if you have this already installed on the front of your oil cooler.  Agree with Ross, in that we'd need to know your MP, RPM, and what altitude(s) and temperatures in which you're operating to give better feedback.

Steve

[GeeBee]

I've had similar issues, running LOP. Your minimum CHT is 250, and mine approaches that on #1 at 65% in the winter. You have no choice, if you want to adhere to the operating limitations. You need to increase power, fuel flow or both. 

[A64Pilot]

41 minutes ago, GeeBee said:

I've had similar issues, running LOP. Your minimum CHT is 250, and mine approaches that on #1 at 65% in the winter. You have no choice, if you want to adhere to the operating limitations. You need to increase power, fuel flow or both. 

Agreed, Even in Summer to keep the cyl head temp in the green I often have to turn the red knob in a little and get closer to peak, of course that increases power, speed and fuel flow, but puts me back in the green.

Cyl head temp follows power output pretty closely and LOP and low RPM and manifold pressure is pretty low power, 22 squared deep LOP puts me at 50% or less.

I’m an IO-360 and have cowl flaps, I will adjust them so they fully close in Winter and open them up in Summer so that they don’t close completely.

I fly down South where it’s never really cold so I’d assume it’s even more relevant if your in actual cold wx.

I don’t do actual cold 

[PT20J]

Various references have stated that the highest oil temps in the engine are about 40 F higher than the temp probe location. You want that to be above the boiling point of water which is 212 F at sea level on a standard day and decreases with altitude (194 F at 10,000’). https://www.thermoworks.com/bpcalc/?gclid=EAIaIQobChMIkLSq4ZGI9gIVjR-tBh05zAaYEAAYASAAEgI6yfD_BwE

[StevenL757]

4 hours ago, GeeBee said:

I've had similar issues, running LOP. Your minimum CHT is 250, and mine approaches that on #1 at 65% in the winter. You have no choice, if you want to adhere to the operating limitations. You need to increase power, fuel flow or both. 

Agree.  Another note for @Little Dipper…flying in Maine during the cold months, I’m regularly at temps on the ground between 0C and -20C, and colder at altitude.  It isn’t uncommon to fly ROP to keep the cylinders above 250F in these temps.

[Little Dipper]

9 hours ago, LANCECASPER said:

There is a cold temperature kit that Mooney makes to slide over and partially block the oil cooler on Ovations to keep the temps up in cold weather.

I have the cold weather kit.  Thanks.

[carusoam]

There is a reference temp around here somewhere…. For the conversion of lead additive to its byproducts…

It may be found doing a search for a paper by Shell oil…
 

We have also discussed the physical limitations in the past… piston, rings, and head tolerances…

 

Now, I have to go read up on min cylinder temps… 

Fuzzy PP memories at best…

Best regards,

-a-

 

[A64Pilot]

12 hours ago, PT20J said:

Various references have stated that the highest oil temps in the engine are about 40 F higher than the temp probe location. You want that to be above the boiling point of water which is 212 F at sea level on a standard day and decreases with altitude (194 F at 10,000’). https://www.thermoworks.com/bpcalc/?gclid=EAIaIQobChMIkLSq4ZGI9gIVjR-tBh05zAaYEAAYASAAEgI6yfD_BwE

This is Lycoming’s class slide.