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Oil temperature question
- Thread starter CamTom12
- Start date
Measure as following image describes. Worn-in bushings are hard to accurately torque.
Think I’d feel better about using drilled bolts and castellated nuts for that application as well.
Then mount your cooler up front and save a lot of fabricating and experimenting. Cylinders need all the air they can get.
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Farmboy
MEMBER
Middlebury, VT
Wes, I’m very familiar with things running hotter than normal. Let me know when I can pick it up. I’ll bring it up north for a year and see if that fixes it. If so, I’ll send a telegram letting you know that it’s fixed.
Peter.
Sent from my iPhone using SuperCub.Org
Peter.
Sent from my iPhone using SuperCub.Org
Schwarz
Registered User
Abilene, Texas Bemidji Minnesota
Ok had a chance this morning to do some testing, used the digital manometer to check air flow through the cowling.
Upper test point
Routing through baffling
Lower test point, tie strapped to motor mount,
[SUB][SUP]
[/SUP][/SUB]
Meter reading,
So it seems that the difference in pressure from upper to lower isn't enough. What are some ways to increase airflow? Sea plane lip is one I've heard recommended, any other ways? Here is a pic or two of my lower cowling area.
Sorry for the fuzzy pic, what else would you check?
Thanks.
Upper test point
Routing through baffling
Lower test point, tie strapped to motor mount,
[SUB][SUP]
Meter reading,
So it seems that the difference in pressure from upper to lower isn't enough. What are some ways to increase airflow? Sea plane lip is one I've heard recommended, any other ways? Here is a pic or two of my lower cowling area.
Sorry for the fuzzy pic, what else would you check?
Thanks.
CamTom12
Registered User
Huntsville, AL
Another test you can do is to unplug first one, then the other tube from the meter to compare upper cowling and lower cowling pressure with static. It helps to have your window or door open for this, otherwise cabin pressure is usually slightly lower than actual static air pressure.
Another note, my meter "normalizes" its pressure differential when I turn it on. This means I have to either turn it on before I crank the motor and keep it awake until I'm ready to take my reading, or I have to disconnect both tubes before I boot it up in-flight. Otherwise I get erroneous pressure differential readings with mine. Not sure if yours works the same but it looks similar to mine.
Go out to the hangar at night and stick a drop-light in your lower cowl. Look around the upper cowl for any light escapes. You will might need a mirror to look through the air inlets with the upper cowl doors closed. That'll check your baffles and rubber seals.
If your baffles and rubber seals are tight, you're either introducing high pressure air into your lower cowling from the free-stream air or you're not evacuating the lower cowl well. From the pictures I'd bet your lower cowl exit is doing both. A seaplane lip will help evacuate the lower cowl and keep the free-stream air out.
A good way to visualize what you need is to take a picture of your airplane from the side and rotate it so that your wing roots are angled like they would be in level flight. Then you need enough lip to create a horizontal "shadow" over your lower cowl exit hole that extends back past where your lower cowl exit hole ends.
Another note, my meter "normalizes" its pressure differential when I turn it on. This means I have to either turn it on before I crank the motor and keep it awake until I'm ready to take my reading, or I have to disconnect both tubes before I boot it up in-flight. Otherwise I get erroneous pressure differential readings with mine. Not sure if yours works the same but it looks similar to mine.
Go out to the hangar at night and stick a drop-light in your lower cowl. Look around the upper cowl for any light escapes. You will might need a mirror to look through the air inlets with the upper cowl doors closed. That'll check your baffles and rubber seals.
If your baffles and rubber seals are tight, you're either introducing high pressure air into your lower cowling from the free-stream air or you're not evacuating the lower cowl well. From the pictures I'd bet your lower cowl exit is doing both. A seaplane lip will help evacuate the lower cowl and keep the free-stream air out.
A good way to visualize what you need is to take a picture of your airplane from the side and rotate it so that your wing roots are angled like they would be in level flight. Then you need enough lip to create a horizontal "shadow" over your lower cowl exit hole that extends back past where your lower cowl exit hole ends.
skywagon8a
MEMBER
SE Mass MA6
Try a lower lip such as this, on this Backcountry Cub. You could attach it to the grey portion of your lower cowl...So it seems that the difference in pressure from upper to lower isn't enough. What are some ways to increase airflow? Sea plane lip is one I've heard recommended, any other ways? Here is a pic or two of my lower cowling area.
Sorry for the fuzzy pic, what else would you check?
Thanks.
Also, how large an opening do you have on your side cowls when they are closed. It should be 2-1/2" to 3" measured at the mid widest point. There is a lot of heat which comes out of these side cowls. I don't have an interior in mine. When I place my hand on the inside of the fabric just below the door it is always very warm. I believe that it actually helps to heat the cabin in cold weather.
This engine is an IO-360 (180 hp) with no cooling issues. The CHT will exceed 400 on a very hot day. This is easily resolved by enriching the mixture. Normal highs are about 380 CHT.
Another view of the lip on the inside.
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Last edited:
Wes,
at cub speeds you’d be doing well if you get in the high 3’s on the manometer, (you’re calibrated to “ of water correct?)
For fun, on your next test run point the nose down till you’re about 115 kts and see what the differential pressure does, because that’s how fast you need to be going, according to lycoming, to meet their recommended 5”H2O.
As cam Tom suggested, check baffling, then a bunch of little mods all start adding up. Lots of info in earlier threads.
But start with:
Timing
Fuel (too lean)
Baffling
I mentioned this earlier, may or may not apply:
My last build I slammed the cowl down as close as the ring gear would allow, Ive seen others do this too,
improves visibility over the nose. Well it also significantly disrupts airflow entering cowl inlets, To the tune of about 20 deg
on the back cylinders.
at cub speeds you’d be doing well if you get in the high 3’s on the manometer, (you’re calibrated to “ of water correct?)
For fun, on your next test run point the nose down till you’re about 115 kts and see what the differential pressure does, because that’s how fast you need to be going, according to lycoming, to meet their recommended 5”H2O.
As cam Tom suggested, check baffling, then a bunch of little mods all start adding up. Lots of info in earlier threads.
But start with:
Timing
Fuel (too lean)
Baffling
I mentioned this earlier, may or may not apply:
My last build I slammed the cowl down as close as the ring gear would allow, Ive seen others do this too,
improves visibility over the nose. Well it also significantly disrupts airflow entering cowl inlets, To the tune of about 20 deg
on the back cylinders.
Schwarz
Registered User
Abilene, Texas Bemidji Minnesota
It's a bit shy of 2.5-3.0 inches,
CamTom, can you explain, not sure what your saying.
Yep, but I may need to go fly it again and play with it a bit, I didn't turn the manometer on until I was sitting in the plane and it was running, I think, but not sure, I hooked up the lines to the manometer after engine start.
Thanks for the replies.
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It looks like you have a outflow problem. This is not uncommon even in stock cubs. The experimental kit makers seem to have a lot of trouble with understanding the need for good air flow. The first thing I would do is a large seaplane lip because it is pretty easy to do. I would say your cheeks are too small but it is a lot more work to replace them and get the paint right so hold off if you can. I would also chase the possibility of air trapped in the cooler ideal mentioned earlier. Have you checked the timing/internal timing of the mags? That is a inexpensive thing to do. If you can afford a 4 cylinder eg/cht you could look at building ramps on the front cylinders but I would not do that unless you can monitor all 4. Thanks for the feedback so far. I am sure you will get this fixed just not sure how much work it will be.
DENNY
DENNY
CamTom12
Registered User
Huntsville, AL
Here’s a not-so-great pictorial example:
If you were to shine a light from directly in front of the plane, my new lip (outlines in red) would create a shadow that extends past the opening in my lower cowl exit (also outlined in red... maybe I should have used different colors, haha).
It made a pretty big difference in my lower cowling pressure as compared to static pressure.
BC12D-4-85
SPONSOR
Fairbanks, AK.
Wes is there a through opening around the air filter element to the rear cowl exit? It would seem that blocking that passage just behind the air filter (or?) might lower the air pressure below the engine. Adding ram air to that area might be raising it is my assumption. Didn't Piper seal that passage?
Gary
Gary
Schwarz
Registered User
Abilene, Texas Bemidji Minnesota
Here’s a not-so-great pictorial example:
If you were to shine a light from directly in front of the plane, my new lip (outlines in red) would create a shadow that extends past the opening in my lower cowl exit (also outlined in red... maybe I should have used different colors, haha).
It made a pretty big difference in my lower cowling pressure as compared to static pressure.
Gotcha, Thanks.
Good question, I'll have to research that, thanks.
BC12D-4-85
SPONSOR
Fairbanks, AK.
Just to make sure I wasn't dreaming I went and looked for the round air cleaner seal...It's a U-shaped hinged plate with edge seal made of felt. Not sure all still have it as one Cub with new engine didn't. Bottom of round filter open but top restricted some. There's more knowledge here than my memories.
If I wanted to seal it today I'd try some round hollow foam water pipe insulation wrapped around the rear filter and tied on for example.
Gary
If I wanted to seal it today I'd try some round hollow foam water pipe insulation wrapped around the rear filter and tied on for example.
Gary
skywagon8a
MEMBER
SE Mass MA6
Gary, Piper did seal that space. I left it off in my Cub just to see what happens and never found a need to put it in as the temperatures all were within my limits. While I can not verify my theory, it appears that maybe the excess ram air which bypasses the round intake filter is actually accelerating the out flowing air thus helping with the cooling. Sort of acting similar to an exhaust augmenter tube?
skywagon8a
MEMBER
SE Mass MA6
It's a bit shy of 2.5-3.0 inches,
IF after trying other things you find that you still need to increase this opening, try adding a "seaplane" lip to the trailing edge of these side cowl doors. You could just duct tape them on for test purposes. Years ago I participated in some cooling tests of a PA-12 on floats to get an STC for an 0-360 (170 hp). To pass the cooling tests a large lip was placed on the bottom opening as well as lips on the side cowls. It was ugly, but it worked.
You could also place some aft facing scoops on the lower cowl as Piper did. This will increase your outlet area with the outside aft facing scoops they will cause lower pressure for additional draw. There are many options for the desired results. The bottom line is to get rid of the heated trapped air.
BC12D-4-85
SPONSOR
Fairbanks, AK.
It's only a guess for or against sealing part of the filter housing. The manometer might offer some info after a quick seal job tho. Piper did seal it for a reason, perhaps for hot and slow A-model sprayers which mine was at one time. Same for the two lower cowl outlets adjacent to the filter housing (see PDF's below).
In winter to -50F I blocked my side cowl cheeks and lower cowl outlets with metal plates. Removed the lower cowl fiberglass seaplane lip from Atlee Dodge, and built a cockpit adjustable shutter for the forward original Piper oil cooler (O-320). Worked well so they all do offer added cooling.
He has two exhaust stacks around which augmenter tubes could be built as another experiment.
Lower cowl outlets:
skywagon8a
MEMBER
SE Mass MA6
Augmenter tubes require a whole different design process. There are specific diameter, length, position of the exhaust exit in relation to the entrance to the augmenter, etc.
What little I do know about this topic is that it would require some major alterations to everything. It is not just a big pipe around the exhaust. It is a sort of venturi effect.
BC12D-4-85
SPONSOR
Fairbanks, AK.
See how Piper did the lower cowl and air filter seal here>>>https://www.univair.com/categories/piper/piper-pa-18/cowling.html?
Gary
Gary
CamTom12
Registered User
Huntsville, AL
I dunno, I think the problem is deeper than just the 3” SCAT to the oil cooler. I think we’re dealing with a couple of things (all airflow related, though).
I think Schwartz needs to increase his SCAT size to the oil cooler to 4” as soon as he has the opportunity. That’ll really open up his oil cooling potential.
I also think that on a cub (I’m assuming has magnetos), cruise CHTs in the 370-380 range are high. High CHTs and high oil temps (plus the picture of the lower cowl exit hole) lead me to think he’s go differential pressure issues in his cowling. Plus the 2” pressure differential that he measured is very low.
But I’m no expert, just my opinion. I moved my airplane (that experienced no temperature issues up north) from AK to the Deep South. Temps are a whole nother animal down here.
I think Schwartz needs to increase his SCAT size to the oil cooler to 4” as soon as he has the opportunity. That’ll really open up his oil cooling potential.
I also think that on a cub (I’m assuming has magnetos), cruise CHTs in the 370-380 range are high. High CHTs and high oil temps (plus the picture of the lower cowl exit hole) lead me to think he’s go differential pressure issues in his cowling. Plus the 2” pressure differential that he measured is very low.
But I’m no expert, just my opinion. I moved my airplane (that experienced no temperature issues up north) from AK to the Deep South. Temps are a whole nother animal down here.
Schwarz
Registered User
Abilene, Texas Bemidji Minnesota
Well making progress, changed the 3" SCAT to 4" SCAT and flew this afternoon, OAT is still 100*f, flew at 2350-2400 about 2500' 800' AGL for 30 minutes. Oil temp stabilized at 220* and didn't increase past that, before it kept going at or above 235* before I got back on the ground. I haven't done anything but put on the larger SCAT, still plan to improve the airflow through the cowling with a lip and address the vernatherm seat, after the weather cools down some.
4"
3"
Back side of my air filter housing is open, don't know if that is hindering airflow or not,
4"
3"
Back side of my air filter housing is open, don't know if that is hindering airflow or not,
Thank you everyone for the tips, its a work in progress to get the oil temps down and tweak the cooling on the engine, its too hot to stay in the hangar long
:roll:[SUB][/SUB]
BC12D-4-85
SPONSOR
Fairbanks, AK.
Above I mentioned seeing factory seals around the air filters on standard Cubs. I've since looked at three 180 Cubs (not Crosswinds STC) and they were also sealed. That's only a for what's it worth comment as I don't know if there's any benefit leaving it open or closed. I can see where any pressure filling or flow disturbance out the cowl caused by an opening might increase local lower cowl pressure. If it were mine I'd temporarily wrap the rear of the filter element to make a seal then go fly and learn something.
Gary
Gary
Steve Pierce
BENEFACTOR
Graham, TX
I run the hoses through the heater box. Make a lip out of posterboard and then you can transfer that pattern to aluminum. Here is a link showing how I have done it. https://www.shortwingpipers.org/for...9-Forming-the-Cooling-Lip-for-the-Bottom-Cowl
Duct tape it and see how much of a change you get.
Duct tape it and see how much of a change you get.
Schwarz
Registered User
Abilene, Texas Bemidji Minnesota
I'm going to do some more testing with the manometer to see how much I can improve the airflow, I think I'm going to wait a couple of weeks and see if the weather changes. I worked late Wednesday evening and early Thursday to try and miss some of the heat. I still carry my roll of duct tape, I will tape it off and do a before and after reading on the manometer. I flew it today, 102 *f and oil temps remained 215-220, much improved.
Thanks.
Thanks.
