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How about another oil temp discussion

Bavafa

Well Known Member
My oil temp trends very closely with most RV14 running a IO390 engine but I am hoping if I can improve it. With that in mind, I build a diffuser for the oil cooler exit and had one flight with it last night which does not seem to have made much of a difference, but it is hard to measure such change.

I have also been checking my oil temp right after shut down by pulling the dipstick and measuring the oil temp. In 5-6 times checking, it seems there is an average of 20-30 degree difference between the temp on the dipstick than what is reporting from G3X. The oil from crankcase is cooler. I have also point the infrared temperature sensor to the oil temp probe body and they all report cooler temp. Any thoughts on that discrepancy?

For a reference, my oil temp in cruise is between 175-200 depending on the OAT and on a climb, I could hit 205-215 going from sea level to 10000 at full power and again depend on OAT
 
did you test the sensor?

Can you test the sensor in hot/boiling water? It would provide one data point. Also, does it match OAT when cold?
 
Just looked up a Lycoming oil flow diagram. It shows the flow from pickup -> pump -> oil cooler (or bypass thru vernatherm) -> passed oil temp sender -> filter -> on to crank case ports.
So is the G3X temp sender reading the 'cooled/temp regulated' reading, and crank case oil temp would be the hot not yet cooled oil temp?
 
For a reference, my oil temp in cruise is between 175-200 depending on the OAT and on a climb, I could hit 205-215 going from sea level to 10000 at full power and again depend on OAT

I think you are beginning a quest to solve a problem that doesn't exist (based on the oil temp #'s you have reported.... and are typical with RV-14's)

Very few (if any) high performance aircraft can fly in a wide range of OAT's and have the oil temp gauge always stuck on 185 F. That is because the regulating range of the vernatherm on a Lycoming engine is rather narrow.... It doesn't come even close to working in the way the coolant thermostat does on your car.

200 Deg or less in cruise during hot OAT's is totally fine, and if you can climb to 10K at max power in the hottest OAT's you would likely encounter, and never exceed 215 F., you do not have an oil cooling issue.
 
Just looked up a Lycoming oil flow diagram. It shows the flow from pickup -> pump -> oil cooler (or bypass thru vernatherm) -> passed oil temp sender -> filter -> on to crank case ports.
So is the G3X temp sender reading the 'cooled/temp regulated' reading, and crank case oil temp would be the hot not yet cooled oil temp?

with oil flowing, that is correct. However, it is possible that the oil in the area of the sensor heat soaks rapidly after the oil stops flowing at shutdown. FYI, your oil temps listed are fine and do not represent a problem, assuming drain intervals of 35-50 hours.

Larry
 
Keep in mind that Lycoming's recommended oil temps are taken at the probe position, not the dipstick. Thus, your temps are in the correct range. If you go much lower, you will not boil off the moisture that collects in your oil.
 
Scott, Bill, Larry,
I understand and agree I don?t have an oil temp problem. But I am on the quest of improving, if that is possible, while it keeps me busy and I learn.
But I am also puzzled to explain the difference in the oil temp from reading the prob and reading it off the dipstick right after shut down. If any, I would have expected to be higher on the dipstick and not lower.
BTW, I have found airflow thru air cooler (i.e. speed) has a lot more affect than reduced power or OAT. One of my highest oil temp I noticed was when I was trying to find my effective ceiling and while I was flying thru FL19-20 and climbing my airspeed had dropped so much that the oil temp was going really high while the OAT was in a single digit. Reducing the climb rate to 300 fpm brought the oil temp down.
 
I have the opposite problem... (although recently I posted here and found out the same information that I DO NOT have a problem). My temps are always 165ish to 175ish. Even here in hot south alabama. I was informed the mfgr has taken all of this into account. The readings as you say are coming from the coolest oil in the engine. The oil temps elsewhere throughout the engine are 25 or so degrees hotter. This is what Mike Busch says in his online videos as well.
 
I have the opposite problem... (although recently I posted here and found out the same information that I DO NOT have a problem). My temps are always 165ish to 175ish. Even here in hot south alabama. I was informed the mfgr has taken all of this into account. The readings as you say are coming from the coolest oil in the engine. The oil temps elsewhere throughout the engine are 25 or so degrees hotter. This is what Mike Busch says in his online videos as well.

opposite problem is easy to remedy, put an oil shutter on the oil cooler. I had one on my RV7 and also on the 14 as well which I do use it in winter time.
 
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