Continuing Problems with Oil Temps

[TS Flightlines]

Larry, just from what you have said, I'd think the hoses were clear.
tom

[lr172]

Originally Posted by vic syracuse

Do you have BOTH the vernatherm and the plunger installed at the same time? I think only one of them should be installed at a time.

Vic

I do. I have the Lyc oil filter adapter, so the V/T seats in that housing and not the hole on the face of the accy case (therefore no mechanical interference w/plunger & spring) The V/T and the plunger essentially do the same thing - they block the flow of oil into the oil filter, forcing it to follow the alternate exit in the primary oil pump feed gallery, which is the feed into the oil cooler. The plunger is just doing it upstream of the V/T. The cooler return line goes to a different chamber of the housing (no V/T interaction) and on to the filter/engine. There may be some negative consequences of having two spring loaded devices to bypass oil if the cooler plugs, but I only did this as a test to isolate my problem and will be removing the plunger or the V/T after testing.

Larry

Larry

[vic syracuse]

Larry, I really don't think you can have both. Take the VT out.

Vic

[lr172]

Originally Posted by vic syracuse

Larry, I really don't think you can have both. Take the VT out.

Vic

Ok, i'll try that today.

[DanH]

Larry has it right. Having both the VT and the viscosity valve plunger installed won't make any difference with the AC-style Lycoming filter adapter.

[scsmith]

I'm wondering if the new hoses, if a different brand/style, might just have a smaller I.D. for the same nominal hose size, because of a different liner. The -6 hose may already be a little marginal, and then, a different brand with a smaller I.D. would be noticeably worse.

I would still consider switching to -8 hoses.


There are very noticeable differences in performance of different brands of coolers. Others noted that this one is a a bit light on cooling fins. If/When you switch coolers again, go with a real Steward-Warner style cooler. The Niagra's seem to be "OK" but not as good as the S-W.

[lr172]

Originally Posted by scsmith

I'm wondering if the new hoses, if a different brand/style, might just have a smaller I.D. for the same nominal hose size, because of a different liner. The -6 hose may already be a little marginal, and then, a different brand with a smaller I.D. would be noticeably worse.

I would still consider switching to -8 hoses.


There are very noticeable differences in performance of different brands of coolers. Others noted that this one is a a bit light on cooling fins. If/When you switch coolers again, go with a real Steward-Warner style cooler. The Niagra's seem to be "OK" but not as good as the S-W.

Good points and ideas here. I had been clinging to the hope my cooler was adequate and didn't want to buy another cooler and fab up a new mounting if avoidable. Seems the capacity is just not there. I agree that the hoses may be contributing some, but I am getting 215 when I want 190. My next course will probably be a cooler and will get -8 lines when I do that. My Mocal as tne AN flare fittings, so need new cooler to swap to -8's.

I have a used SW 8406 cooler. I had struggled to get all of the crud out if it, but now thinking I'll flush it a again and try it. It sits upstream of the filter, so if there is a bit of debris left, it will get caught by the filter.

I am still hoping others may offer ideas to improve the airflow through my current filter to improve performance. Does consolidating adn directing the exit air from the cooler help?

Larry

[DanH]

Originally Posted by lr172

I am still hoping others may offer ideas to improve the airflow through my current filter to improve performance. Does consolidating adn directing the exit air from the cooler help?

Consolidating and directing, no. What matters is pressure at the exit side. A duct can be used to port the exit to a region of lower pressure. If increased pressure delta provides more gain then the frictional duct losses subtract, the result should be more mass flow.

[scsmith]

I don't think you gain much from any kind of splitter that shields the flow into the cooler from the flow into the cylinders. That flow has not picked up very much heat yet.

The cooler is just exhausting into a 'plenum', the open space behind the engine baffles, so the cooler exit pressure matches the local pressure there.
A well-shaped diffuser duct on the cooler exit would make the pressure at the diffuser exit match the local pressure, thus the pressure at the cooler exit is lower, and air velocity higher.

BUT....

The space you have to work with is limited, and it is easy to make a poor diffuser. You could give it a try if you want. I would make a short diffuser, maybe 3" or 4" long, with about a 10-degree angle. In case you are unfamiliar, the diffuser duct is just a short section of tapered rectangular tube where all four walls are sloped about 10 degrees and the small end of the tapered tube fits your cooler exit, and the other end of the tube is bigger because of the slope of the walls. There is nothing really magic about 10 degrees. For very long diffusers, something like 2.5 degrees is the limit. For very short diffusers, up to 30 or 40 degrees can work, but generally have a lot of pressure loss. 10 degrees is a moderate diffusion angle for a short diffuser that should give you good pressure recovery.


I don't know the exit area of your cooler, but just as an illustration, if the cooler exit is 4" x 6" (24 sq in.) then a 3" long 10-degree diffuser would have an exit of 35 sq in. almost 50% increase in exit area compared to the cooler exit. That means that, assuming no diffuser pressure loss, the velocity through the cooler would be roughly 50% faster. Of course there are diffuser losses, so the velocity doesn't increase quite that much.

[DanH]

Originally Posted by scsmith

I don't think you gain much from any kind of splitter that shields the flow into the cooler from the flow into the cylinders. That flow has not picked up very much heat yet.

It does pick up some. Data from five years ago, taken during a trip to Jackson MS. Temp probe located at the face of the remote cooler, as compared to OAT under the wing. They were very close in the hangar. The OC air was taken from the rear baffle wall with a 4" SCEET:

Morning OAT 64F @ 8500 ft
Oil cooler inlet probe 81F
81-64= 17 degree rise

Afternoon OAT 86F @ 2500 ft
Oil cooler inlet probe 101F
101-86= 16 degree rise