How much will oil temp drop after break in on an IO390?

[Desert Rat]

Let me preface this question by saying I'm sure there's some low hanging fruit to be picked with airflow improvement and sealing the engine baffles a bit tighter and whatnot, but I'm curious how much of my slightly elevated oil temp is just a result of a new engine being run hard. I know that 390's carry away a lot of heat in the oil, but this is the first one I've ever flown behind and I'm unsure how much to expect the temp to come down as everything wears in.

I'm not planning to take any drastic action until it settles down, but like I said, I'm curious how much work I have ahead of me.

Today's flight was 80 OAT at 4,500 MSL. I was running 25/25 at 75% power and had leaned to 14.5 gph in level cruise flight. IAS was 156 kts (without wheel pants). CHT's were 350*f, EGT's were 1,300*f. Oil pressure was 73 psi and oil temp was 211*f.

 

[Full Throttle]

How many hours on the engine?

 

[Bavafa]

You should expect better temps once you install your wheel pants, the additional speed will help much but as it is, that is not too bad for a 80F OAT
For improvement, you might one to consider changing it to a 5" scat tubing to the oil cooler if you have a 4" scat tubbing, that should also help.

Congrats on getting to the 10 yard line

 

[1949MGTC]

Virtually identical to my engine early on. Magic happened after fairings and wheel pants after 50 hours. Oil temp dropped 15 to 20 degrees

 

[Desert Rat]

Hey guys

- 6 hours on the hobbs 3.7 on the tach

-I can't fit a 5" scat without heroic efforts. it's a 390 shoehorned into a RV7 with a 13 row cooler in an RV10 plenum on the pilot side firewall and it's really tight back there. I do have some room for improvement with duct routing though and can eventually go to skeet which is smooth on the inside for better flow, but it's also $$$ more than scat, so here we are for now.

- 20* drop would be awesome. I'm looking for that magic 180* number and that would get me most of the way there.

 

[D-Dubya]

Go ahead and do the things now that you know are going to help cool the oil. You're probably going to end up doing them eventually anyway.

1. If the baffles can be sealed better, by all means do that. It doesn't take long and the RTV will cure overnight. With that said, your CHTs look pretty good.
2. Put your pants on. I've never fully understood why many fly without their pants and gear leg fairings on for Phase 1. Even with higher power settings to break in the engine, you're not going to exceed Vne unless you're getting into very unusual attitudes. My pants have been on since the first flight. I'll probably get shot down for that and people will wonder how I'm not a smoking hole in the ground. Anecdotally, one of the past well-known RV-7 guys actually had the thin bracket that holds the wheel pants break during Phase 1, as it apparently was fluttering in the wind. He had to get another and go through all the hassle of installing it again.
3. There are indeed improvements that can be made to the hose going to the oil cooler. SCEET does have slightly less pressure drop than SCAT. In my opinion, it's worth the cost if it gets you a little improvement. And as BAVAFA referenced, bigger is better. But it's also more work to change sizes.
4. Double check your cooler to make sure that piece of trash didn't find its way in there and could be obstructing oil flow. But given the conditions you listed, you're not crazy high on oil temps.

I just saw your last post and I think 180 is unrealistic for the summertime. Nor is it necessary or beneficial. Most of us would be perfectly happy with 190-195 degrees F in the summer.

 

[Desert Rat]

Hey DW- you won't get shot down by me. I fully agree that I should have wheel pants on. My excuse is that I left them off for the first flight due to wanting to burn the brake pads in on the long taxi to the takeoff end of the runway. Well, that and I'm just tired of fiberglass work and don't have the intersection fairings done yet. At this point it's not much of an excuse and I'll get them on soon. I have the gear leg fairings on though

180 is a stretch goal for sure, but it's something to shoot for. Lycoming says 180 will get you max engine life and I have no reason to doubt them. I was thinking about this last night as I was doing touch and goes with a student in a 172S. It was close to 100 degrees in the pattern and that thing was rock solid at 180 start to finish. I know that's not an apples to apples comparison, but I do think that I can get close to that with enough shade tree engineering and I aim to eventually squeeze out every bit of cooling that is achievable. In addition to being nice to my engine, it will be fun to try.