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IO-360 PV high oil temp

RV7 To Go

RV7 To Go

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Looking for suggestions from the group on my higher than I like oil temps on my RV-8. The oil temp has run as hot as 210F in a 3500' cruise at 65% power (about 24 square) with an OAT of 75F. Yes, I know the temp is still in the green but I like to see 180-185F. The cooler is mounted on the engine mount fed through a 4" SCEET duct. CHT's are always in the low 300's in cruise and never see 400 even on a hard climb. The engine is an IO-360 PV with 85 hrs on it. Compressions are high 70's and oil consumption 1L/12 hrs. Oil pressure is 87 PSI hot. Prop is a WW 300 series 3 blade.

So the other day... 100kt climb to 5500' on a 75F day and a warm engine with oil temp 170F at startup. Oil temp 201F at 5500'. Highest CHT 390F. In cruise at 148 KIAS at 24 square LOP the oil temp came down to 185 in about 15 min at 55F OAT. When descending to 3500' the temp rose to 190F with no power change. Descending to 1900' (cct alt) and bringing the power back the temp climbed to 195F. Seems weird to me that when I reduce power to slow down when entering the cct the temp rises. By the time I am on the ground and the short taxi to the pumps the temp was 200F. The Anti-splat shutter was open the entire flight.

What I have tried:
- changed from a 7 row to a 9 row Aero Classic cooler and used 4" SCEET instead of SCAT- slightly better but still 195-200 on a hot day
- checked the cooler/engine fittings were full open when changing the cooler
- verified temp probe accuracy
- changed Vernatherm - no change
- cut the cowl discharge opening square - no change
- installed .024 injector nozzles, cleaned all injectors and checked flow - no change
- baffle seals are as good as I can get them

I haven't removed the shutter since I am sure I will need it for the cold weather ops coming shortly.

Any ideas would be appreciated!
 

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Does the right angle duct have diffuser/turning vanes inside? Looks like a pretty abrupt transition from the outside.

Oil cooler optimization

I'm looking to further optimize my oil cooler setup, in a ROP cruise I'm seeing temperatures between 210-220 *F at OATs of around 40*; CHTs in this cruise regime are 380-390*; my engine is a parallel valve 320 with piston squirters. My cooler is a 7 row Aero Classic (PN 8000075) supplied by -8...
www.vansairforce.net
 
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Mikeyb said:
Does the right angle duct have diffusers inside? Looks like a pretty abrupt turn from the outside.

Oil cooler optimization

I'm looking to further optimize my oil cooler setup, in a ROP cruise I'm seeing temperatures between 210-220 *F at OATs of around 40*; CHTs in this cruise regime are 380-390*; my engine is a parallel valve 320 with piston squirters. My cooler is a 7 row Aero Classic (PN 8000075) supplied by -8...
www.vansairforce.net
Click to expand...
Nothing in the duct. Just wide open except for the shutter on the front which is confirmed wide open.

As per the writeup...85 hrs on the engine since OH.
 
RV7 To Go said:
. In cruise at 148 KIAS at 24 square LOP the oil temp came down to 185 in about 15 min at 55F OAT. When descending to 3500' the temp rose to 190F with no power change. Descending to 1900' (cct alt) and bringing the power back the temp climbed to 195F. Seems weird to me that when I reduce power to slow down when entering the cct the temp rises. By the time I am on the ground and the short taxi to the pumps the temp was 200F. The Anti-splat shutter was open the entire flight.
!
Click to expand...
Above 185, you are full flow through the cooler and sump temps are probably 210 or so. As you slow down, the airflow over the cooler reduces. Therefore the oil doesn’t shed as much heat as it did at higher airspeeds. The OT is measured as it comes out of the cooler, so it is not a system temp, but a post cooled snapshot temp. The ot rose to 195 because the cooler was less efficient with a lower airflow rate. Due to the lower airspeed. The overall oil temp isn’t changing, just the efficiency of the cooler is reducing and this raises the post cooled temp. You only notice this phenomenon when ots are above 185. Otherwise these changes are modulated via the thermostat.

My speculation is that you have too much turbulence in your air duct setup and this is reducing actual air volume through the cooler. Those transitions are pretty sharp and sceet is known for creating a lot of turbulence also.

There may be ways to clean all of that up, but might be easiest to mount the cooler on the baffle. When steps are taken to reinforce, cracking doesn’t happen.
 
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To me your oil temperature is fine. I have the same engine airframe but the stock cooler on the baffle. I did the same flight today in the same conditions. My oil temp was 185 max with half the oil cooler taped up. If you want it lower you have to work on your plenum/duct design
 
RV7 To Go said:
I run 6 quarts and fill at 5. Phillips Victory 20-50.
Click to expand...
Oil temps climb faster when using 5 to 6-quarts vs the recommended 8-quarts and would probably stabilize higher, too. I run with a simple drain-back style oil/air separator and always fill to 8-quarts (7-min), and I don't lose oil though the breather with an oil/air separator. Thinking this might just help lower your oil temps back down to around 195 F, especially during the summer months.

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Mikeyb and I have the same engine, and we have the same oil coolers mounted at the rear of the baffle. My oil temperature was below 190degF even when flying in warm SoCal weather and in mostly in the same temperature range as his. I fly in much hotter weather condition in the desert than Mikeyb. Like he said, find ways to clean up the oil cooler plenum.
 
lr172 said:
There may be ways to clean all of that up, but might be easiest to mount the cooler on the baffle. When steps are taken to reinforce, cracking doesn’t happen.
Click to expand...
I have my oil cooler on the baffle, and have added a lot of reinforcements, but still get cracks. I do have very low oil temps, but I would not recommend moving the oil cooler to the baffle. Or ever installing it there. Look at the RV-14 and do it that way and you will have a good system.

Also, it looks like the anti-splat shutter is installed on the baffle. This will cause a lot of turbulence in the ducting down to the oil cooler. I'd put it right in front of the oil cooler, if you can make that physically work. Can't hurt to try it without the shutter for a few flights to see the impact.
 
Has anyone mounted their oil cooler right up against the baffle behind the #4 cylinder, but not physically attached to the baffling?
This would require a "rubberized gasket" to ensure all the air goes to the cooler, and then all the cooler mounting would be done on the engine mounts. This would be similar to the Showplanes method but without the plenum and not on the #3 cylinder.
Would love to see pics and/or plans for alternate oil cooler mounting on the RV-8 as I have the same issue with bad airflow to a firewall mounted cooler (Sceet ducting making bends).
 
rv8ch said:
I have my oil cooler on the baffle, and have added a lot of reinforcements, but still get cracks. I do have very low oil temps, but I would not recommend moving the oil cooler to the baffle. Or ever installing it there. Look at the RV-14 and do it that way and you will have a good system.

Also, it looks like the anti-splat shutter is installed on the baffle. This will cause a lot of turbulence in the ducting down to the oil cooler. I'd put it right in front of the oil cooler, if you can make that physically work. Can't hurt to try it without the shutter for a few flights to see the impact.
Click to expand...
Not sure what the differences are in reinforcement across builders. I have 1600 hours with no cracks on my 6. Have seen other posts with builders having long term success with reinforcement. I am sure there is a contingent that doesn't have success. Clearly that method works well from an airflow perspective. At some point, it would be valuable to have a thread comparing approaches to this issue.
 
If you're wanting to stick with the current oil cooler location, then the easiest thing to try would be replacing that fiberglass inlet piece from the rear baffle to the hose. As others have said, that's a pretty abrupt directional change that will almost certainly cause some pressure drop. Even if you don't have access to a 3D printer that can make internal turning vanes, you could still make improvements with some gradual curves going to the 4" hose. You can easily shape rigid foam into the shape you need and use that as a form for fiberglass layups.

And yes, skeet has slightly better flow characteristics that scat, so go with that as well.
 
I don't see a problem here. I've got a 390 in my 7 and extended climbs on a hot day will see the oil temp hit 220. The key is that temp is transient with 3-5 minutes at level cruise the only temp settles at 185. I think you're fine. I use 6 qts of Philips Victory 20-50.
 
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