Oil temps running warm on climbs.

The warm weather is back again, here on the West Coast.

We are looking for ideas or suggestions on fabricating ways to distance the oil cooler up front a little bit farther away from the muffler pack of the exhaust system, for more cooling effect.

What avenues have people gone down to do this? I assume no one cuts and rewelds the exhaust system, so, to me, the logical solution is to cut out a portion of the cowling to move the oil radiator further forward into the inlet of the cowling, and lengthen the oil hoses a bit to compensate?

Thoughts on how'd you approach and handle it. I've no love for fiberglass layup, but if it has to be done, it has to be done. Proper temperature oil is the lifeblood of a very expensive Rotax engine, there's a lot of mountains around us with desert, sometimes you can't just decrease your climb rate, unless you want to look like a Cessna 150 flying in circles to gain elevation. That's not very "RV" esqe performance.

There have been several threads discussing this issue. I have an early SN 12 with muffler located just behind the oil cooler. On hot summer days, with two onboard and extended climb, I see oil temp in the yellow arc for several minutes even after leveling in cruise. Temps always come back into the green, albeit high green on hot days. Yellow arc is yellow arc ? not red arc. You can run in the yellow arc for a period of time so long as condition corrects itself. Oil can be operated as high as 250F but conventional wisdom says upper limit should be closer to 230F. Best to run oil hot enough to drive off moisture contamination from combustion process.

The Rotax engine design has a sealed crankcase and only the oil tank is vented to atmosphere. This is a real plus. Continental and Lycoming engines have vented crankcase that ?breathes? when engine is not in use. Humidity from the air enters crankcase and causes rust and corrosion on internal parts as they cool.

Niner-

Here is a link to a thread containing some photos you may find helpful. I know there was another set of photos somewhere that were much more detailed but I had the link to this one bookmarked.

http://www.vansairforce.com/community/showthread.php?t=89532&highlight=moving+oil+cooler

If I remember correctly, those that have moved the oil cooler have only moved it forward about an 1" to 11/4" and were able to use the standard oil cooler hoses.

Happy flying,

Thoughts on instead just running E10 Mogas and running a full synthetic motor oil instead, maybe the Mobil 1 T4 Motorcycle 10w-40 oil?

Is there an adjustment to run the muffler as far aft as possible to provide a bit more clearance?

Is there an adjustment to run the muffler as far aft as possible to provide a bit more clearance?

Click to expand...

Niner-

There is no real adjustment per se ... however, that said, there is some aft movement (but not that much) that can be created when installing the springs.

To the best of my knowledge, Van's has provided three exhaust systems for the 912ULS engine.

The original version on older RV-12's placed the muffler very close to the oil cooler ... the exhaust pipe exits the lower cowl at an aft angle.

The second version has different exhaust pipes (perhaps muffler too) and moves the muffler slightly more aft ... the muffler's exhaust pipe exits the lower cowl straight down (this is the version I have ... my RV-12 was one of the very first to adopt this version from Van's).

The third version (which I'm not sure what changes were made) has the exhaust pipe exiting the lower cowl at an angle canted aft ... much the same as the exhaust on the original RV-12. This was mentioned here on VAF last year or so by Scott at Van's in a thread talking about the exhaust system changes on the 912ULS.

If you have one of the latter two versions and need more oil cooling, perhaps you could improve oil temps by adding a heat shield plate between the muffler and oil cooler. I would think a plate close to the muffler would really help ... and may not even need to be that big if you are only trying to bring the temps down a little more.

Just a quick word of caution? be careful if you decide to move muffler aft. Check for muffler / oil drain line clearance. Muffler, in some installations, is very close to oil drain line elbow on bottom of crankcase. I replaced with Aircraft Specialties Conductive Teflon hose with Banjo fitting for extra clearance.

Good tip on the Banjo fitting for more clearance.

We had the same problem with an older RV-12 and tried changing thermo couples, shielding but nothing seamed to work here in Bakersfield, CA. We talked to Vans last year and bought a new muffler that is set back away from the oil cooler. So far no more problems. I think it was around September when we put it on so the weather was starting to cool off. So now, we are just coming into the "Hot" season and it will get a real test. I'm pretty sure we got the problem solved (minimized).

Let us know how that goes taking off on a 25-30 C temp day, with 4 minutes of climb near 1320 # at Vy