View Full Version : Oil temps
06-15-2008, 11:06 PM
I'm still on the very steep learning curve on my Rocket and would appreciate some advise. If possible can you guys who are flying post your typical oil temps? I believe mine are a bit high but I'd like to know what I should be expecting before I go chasing a solution. On my last flight I was seeing 220 at a power setting of 24 in/2400 rpm @ 3000'. The OAT was 28 deg C. Reducing the power to 23 in/2400 rpm brought the temp down to 215. On a straight climb @ 120 KIAS from 3000' to 6000' at full power the temp hit 225 and then came down to 212 in cruise @2300 RPM. I forgot to log the OAT at 6000'. From 6000' I made a decent into the pattern. The oil temp never went below 200 and was 215 when I shut down. Through all this the highest cyl temp was 405 at the top of the climb and they were 370-390 in cruise so I think I have good airflow through the cowl. What do you guys think?
I don't think your temps are unreasonable. I like to see the oil run between 190-210 in cruise. yours might be a little on the high side but still within "my" limits. I consider 230-240 my upper limit. I'd much rather see them on the high side than too low. 180F is my minimum.
06-16-2008, 07:49 AM
With a plenum, I almost never see oil temps over 200 dF, even in summer. Cylinders are typically around 340 dF to 370 dF range. In a 24 square cruise at 3K, I'd be surpised if my oil got to 180 dF.
The plenum sure helps but what really got the temps down was smoothing out the airflow on the top of the cowl. I also installed rounded ramps in front of the cylinders to route the air up and over the front cylinders. I also cut the bottom edge of the cowl back about an inch to allow for more exit area.
I think your numbers are in the acceptable range given the heat in Florida, but you can probably make them a little better with some fiddling. BTW, you never stop fiddling.
06-16-2008, 06:18 PM
Sent you a PM essentially agreeing with the two previous folks.
08-30-2010, 03:28 PM
F1 Rocket, Did your temps come down? If so after how many hours?
This is an old thread, but might be interesting to those breaking in a rebuilt engine. A few more data points for others having trouble.
Sadly, I can't offer any solutions. I have read a bunch of threads on this site and have come to no conclusion. Interesting how many opinions there are on this subject ranging from a meticulous step by step process (usually referred to in another thread) to "Fly the bleap out of the airplane". I had several issues on the ground before my maiden voyage, increasing the likely hood that I have glazed cylinders.
I have an O-360-A1A with a VS prop. I have Superior Cylinders and a Lycoming Case. Hartzel Blended Airfoil 7497 prop. I have only Mags (Bendix). I now have about 14 hours on the engine. My outside air temps are between 100 and 108 degrees F. (I live in the Dallas/Ft worth metro area). It is August. My CHT are between 350 and 395 at about 24" and 2300 RPM. My oil temp is about 210-215. I am hopeful that the rings will seat soon. The engine performs well and delivers over 2K per min in a climb (28" 2700). Of course I can't enjoy that but for a minute and must level off and drastically reduce power (to about 20" and 2100). If I don't arrest the climb, the oil temp hops up to 220 and is moving fast to 230. The hottest CHT moves past 415 with the rest of the cylinders around 390 - 400. I can lean at power settings below 75% (2500 to 3500 msl and a fuel flow rate of 9 gal/hour), but the temps will be begin a slow climb upward in cruise and after about 15-20 mins, I must reduce power settings down in the 20 / 2100 range and enrich a bit to reduce the oil and chts.
The #1 and #3 cylinders are 35 to 45 degrees hotter with the #1 cylinder being the hottest. I am using Aeroshell 100 oil.
I will report back at 25 - 30 hours and again at 50 hours.
08-31-2010, 11:34 PM
When I bought my HR2 I had 15 years of RV4 and other RV problem solving behind me. My HR2 exhibited the same symptoms yours had so I started with a tape measure. I measured my standard Harmon cowlings inlets and exhaust area. An acceptable ratio I like is exit area 1.2 times greater than inlet. This solved my RV4's issues along with a larger oil cooler and tighter baffling.
On my HR2 I cut out a U shaped section of my lower cowling lip increasing my exit airflow area by 15%. This brought my cruise CHT's down to a 323 average running 10 LOP with numbers as low as 285 at low power settings. Climb CHT's never exceed 385.
My oil temps at altitude and LOP in summer run 185-195 and never exceed 215 in climb even out of Leadville CO Sunday afternoon. One fix that worked for Oil Temp was the Airflow systems RV-10 oil cooler sold by Aircraft Spruce. Far superior to the SW I ran before. I installed it aft of the left rear baffle tilted at a 30 degree angle with #8 lines.
All this combines for heat reduction and very efficient cruise numbers. I just completed my annual Swamp to Idaho backcountry jaunt with some impressive numbers.
If you have any questions, contact me off line, I'd love to help.
09-02-2010, 12:21 PM
I typically run 105C-115C, 220F-240F with my Aeroshell 15-50 semi-synthetic.