hecilopter

hecilopter

Well Known Member
In an effort to solve the never ending question of why airplanes which are similarly configured have such widely varying oil temps, just looking for data from local observations.

It has been noted that engines equipped with piston squirters will have higher oil temps, so we need data from engines without piston squirters.

Locally we have 3 unpainted engines (and one with the thin lycoming gray), all run oil temps in the 160 - 180 F range, even with ambient temps over 100 F.

Then there are 3 painted engines, esp. the oil sumps, varying colors, red, blue which all have oil temps 200 - 240 range even with ambient temps in the 85 F + range.

All configurations are the standard #4 mounted van's oil cooler, baffling, etc.

Looking for 2 data points just to see if this is an anomaly or if there may be something to it. No need to reply if you have piston squirters. Looking to see if maybe the painted sump is acting as an insulator and holding some heat in.

1. How many unpainted engines out there with high oil temps (200 F+) ?

2. How many painted (not the thin lycoming gray) engines with low oil temps (<185 F) ?

If there are several replies then no need to research this one further, just curious and trying to figure this out.

Thanks!
 
Last edited:
Thanks for the article

Excerpt:

One more finding from the NACA reports; to further aid cooling, you should paint the engine with a VERY thin black enamel. The paint should not be thicker than .002 " This will improve cooling by three (3) percent over bare metal. If the paint is thicker than .005" you get no benefit and in fact thicker paint will insulate the cylinders. Use black RTV for the wraps and paint everything under the cowling with a thin coat of black high temperature grill paint.


This is great info and at least partially confirms my theory.
 
Last edited:
Rusty,

I am also curious if those who apply the "heat shield" AKA foil tape to the interior of the cowling has an additional insulating (resulting in higher temps) effect.

I did foil tape mine and am thinking that I am going to remove it.
 
I used foil tape

to protect my cowling and I'm running very cool. I also had my exhaust ceramic coated as another data point. It works so well, I can shut the engine down after a flight and get out and grab the exhaust where it exits the cowling without burning my hand!
 
oil temp

If you are still getting Boomer sized oil temps, try changing the vernatherm ? sp?,,, I have heard on good athority that might just fix the problem
 
Just curious about what results you're going to get. I'm thinking there are a lot more variables than whether someone uses piston skirt squirters or not. What about Cylinder Head bore material? Compression ratio? Elec. Ignition? Fuel Injected or Carb? Oil type? Oil pressure? etc, etc, etc.

There are way too many variables to make pinning oil temps on one or two things. I'm guessing it's a combination of all of the above, or at least a majority subset of all the variables.
 
I think you would have to include power setting as a variable, my temp at 65% or less is usually 185 with temps in the 100 oat range. Higher power settings and higher oat's mean higher oil temps. I've never seen more than 210 with a power setting of 75% with oat of 109.
Engine has thick coat of red paint, everthing is painted except the cylinders.
SW oil cooler.
 
Red paint

Walt, one of the red painted engines has temps very similar to yours. It is an eci as well. It had piston squirters and temps were in the 225 - 235 range at 75%. Those cylinders were removed due to the crack inspection AD. The piston squirters were plugged and now the temps are down almost identical to yours.

My engine is unpainted and I can run WOT at 2000 msl and 2700 rpm with an oat of 100 and my temps struggle to get to 180. Any lower oat and they won't see 170. The other 2 unpainted engines have temps very similar to this flying side by side.
 
I actually had a similar problem, where if the OAT was lower than 90-degrees or so my oil temps wouldn't get past 170 (and that's if I ran it really hard). I thought I had an oil temp problem of the other extreme - too cool.

Then I discovered that I had the wrong sender selected in my EFIS. Doh! :eek: That brought my temps up into the low 200's. Just another variable, I suppose.
 
lostpilot28 said:
I actually had a similar problem, where if the OAT was lower than 90-degrees or so my oil temps wouldn't get past 170 (and that's if I ran it really hard). I thought I had an oil temp problem of the other extreme - too cool.

Then I discovered that I had the wrong sender selected in my EFIS. Doh! :eek: That brought my temps up into the low 200's. Just another variable, I suppose.
Click to expand...

Along that same line when I changed my Van's oil sensor/gauge to EI my temp went up 20 degrees, the EI is correct.
 
My engine is painted Lycoming gray and runs cool.

The key to adequate cooling is more a factor of exit area and not the color of engine paint. Reduce the pressure in the bottom cowl area and more air will flow through the cylinders and oil cooler. This seems so basic.

Just my 2 cents worth. It works here.
 
You must log in or register to reply here.