Oil Line sizing

[lr172]

I am rebuilding an O-320 for installation in my RV-6. The engine came from a twin commanche and it had -6 AN fittings for the oil cooler lines. I acquired new AN fittings and hoses in this size for the oil cooler and remote oil filter that I am installing. Today I noticed that Van's plans suggested -8 lines for the oil cooler and that is consistent with what I have seen in my automotive experience.

Are -6 lines adequate for this application? will I cause starvation or just limited oil flow through the cooler? Can this reduce my ability to cool the oil?

Curious others opinions with more experience than I.

Thanks for any assistance that you can provide.

Larry

[az_gila]

The Grumman Cheetah (150 HP) and Tiger (180 HP) both use -6 sizes hoses from the engine to and from the oil cooler.

Field modifications to reduce oil temps usually involve a larger oil cooler rather than larger lines.

[TS Flightlines]

Larry---for most RV applications, we build -8 cooler hoses. On a few occasions with 320's ive seen some -6's, but most were 8's.
Tom

[Toobuilder]

Though the -6 lines will work (obviously), I'd say you need to make sure that you keep them as short as possible to minimize line losses. That said, the fact that you are also running a remote filter leads me to believe that you are going to have a lot of hose running around... The -8 would give you more margin there.

I'm not familiar with any actual testing being done, but pumping cold, thick oil through "fuel line" sized hose seems like it's asking for problems.

[lr172]

Thanks for the guidance here. I am only planning 3 hoses of about 1.5' - 2.0' apiece. I am not too worried about the cold oil situation, as the Vernatherm will bypass the external oil routing when the pressure in that circuit is too high and that is built into the design of the Lycoming Oil system. Further, the Vernatherm won't even route oil through the external circuit until the oil temp reaches 85*C. My bigger concern was overall flow impacted by line size at temp.

I may try it and see what happens. If I hadn't already ordered the hoses and fittings I would go with -8. However, I have $100 invested in the -6 lines and hoses already.

Larry

[Toobuilder]

For the cooler circut, maybe... But what about your oil filter? Is that part time too?

And for what it's worth, I think 2' hoses are on the long side. I worked on the routing on mine and got them both down to under a foot each (and no 90 degree fittings either).

[lr172]

Originally Posted by Toobuilder

For the cooler circut, maybe... But what about your oil filter? Is that part time too?

And for what it's worth, I think 2' hoses are on the long side. I worked on the routing on mine and got them both down to under a foot each (and no 90 degree fittings either).

Yes, cooler and filter will be on the same external circuit and that circuit is bypassed by the vernatherm when < 85* I feel this will adequate, as many of these older engines have no oil filter. The oil will end up being filtered ~80-90% of the time. The engine still has the main screen to filter contaminants as well as a screen in the sump.

I hope that I can get my lines to around a foot. However, my engine isn't mounted yet, so haven't made measurements or determined final routing. Do you have a picture of your setup?

Larry

[mahlon_r]

be aware that many installations will not achieve anywhere near 85C when the ambient is below 30F even with blocking off the cowl inlets with winterization plates. So you may not get the oil filter online during the colder operating ambient's.
Merry Christmas and Good Luck,
Mahlon

[lr172]

Originally Posted by Toobuilder

For the cooler circut, maybe... But what about your oil filter? Is that part time too?

And for what it's worth, I think 2' hoses are on the long side. I worked on the routing on mine and got them both down to under a foot each (and no 90 degree fittings either).

Michael,

Would you mind sharing a picture of your oil line routing? I would like to leverage your efforts/experience here if you don't mind.

Thanks,

Larry

[Toobuilder]

I can try Larry, but it will be tough to see any detail since the engine is hung. Taking the prop off today, so I'll see what I can do when the cowl is off.

Not much detail in this thread, but you can get a glimpse of the setup I have.