High oil temp

I have been having high indicated oil temps with my newly finished RV-7. I have the Garmin G3X. All other engine indications are normal.

I have the Aerosport IO-375 with 9.5-1 compression, and after searching here have found that others with this engine have also sometimes had temp issues.

We have checked the vernatherm. I even replaced it just to be sure, with no change.

Today we wired up a steam gauge to a separate probe to see if it was an indication problem. The results were interesting.

The engine has about 42 hours on it now.

At 74% power, 25" at 2300RPM, 3400' MSL, 66 degrees OAT, leaned 170 degrees rich of peak this was the result:

CHT's: 356 357 338 341
EGT 1235 1205 1205 1200

Oil pressure: 67 psi

Garmin oil temp 225, steam gauge temp 205

I tried it again at WOT, 90% power 27.3" at 2630 RPM, full rich mixture

CHT's 358 369 338 342

EGT 1215 1185 1180 1180 (maybe a different injector for #1 is in order)

Oil pressure: 65psi

Oil temps: Garmin 239, steam gauge 218

So a twenty degree difference between the Garmin and the steam gauge.

I have a 9 row cooler and am thinking of going to a 12 row from Airflow Systems, but I have two questions:

#1) How to tell which gauge is the more correct gauge?

#2) Is there a way to recalibrate the Garmin gauge if it is the one reading too high?

Boiling water or silicone oil with a lab thermometer and heat gun both work well. If you are well above SL the hot oil may be more accurate. Depending upon where you are measuring OT with the two probes it's very possible both are accurate.

EDIT: just noticed you are in FL so likely not more than 50' MSL )

deek

Hopefully you have solved your problem by now...sorry for the late reply. I had high oil temps when I started flying my -6A (O-320D1A), oil cooler on the firewall. I tried a bunch of things but what solved the problem was adding louvers to the bottom of the cowling. The exhaust pipes and nose gear leg structure take up a whole lot of room in that opening in the bottom of the cowl, and the air couldn't get out of the area between the baffles and the firewall.

Jim Bower
RV-6A N143DJ

... You may want to go to our website and have a look at our new EZ Cool that addresses these types of problems. Installing louvers will slow you down with unnecessary drag. Thanks, Allan....

Signal ground for oil temp

I just resolved this with my -10 with the G3X with help from Chris @ Steinair. Maybe it's your issue too. Verify that the oil temperature probe is grounded with a signal ground and not a airframe ground or backshell ground. The gauge will read hotter than actual temperature. Mine was off by around 20 degrees in my case. It was great to find out I didn't have a cooling issue, just a instrumentation issue.
Good Luck!

Regards,
Don Orrick
N410JA