The smaller hose diameter is a clever way to bias oil flow through the vernatherm opening, i.e. more oil bypasses the cooler.
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Oil baffle and oil temps
- Thread starter Saville
- Start date
The smaller hose diameter is a clever way to bias oil flow through the vernatherm opening, i.e. more oil bypasses the cooler.
WingsOnWheels
Well Known Member
I have the same low oil temp issue on my carbed, parallel valve 360. Couldn't get oil temps over 165 in the winter. The weather here in Texas varies so wildly I didn't want to use tape or a blockoff plate.
I had designed my own shutter, but before I finished a deal came along for an AntiSplat shutter, so just went with that. I mounted the shutter to the rear of the cooler for the same reasons noted by others (rivets in the way, etc). Somewhat less effective on the rear, but I just need to reduce the flow a bit.
So far it has worked perfectly. Haven't had any really cold days yet, but on the cool days I can get temps to >180. When I left Petit Jean, the temps were moderate. I forgot to reopen the shutter before departure, oil temps topped at 200 with the shutter closed during cruise-climb. Dropped back to about 180 as soon as I opened the shutter some. I have run it during hot Texas days without any high oil temperature issues (shutter open).
I had designed my own shutter, but before I finished a deal came along for an AntiSplat shutter, so just went with that. I mounted the shutter to the rear of the cooler for the same reasons noted by others (rivets in the way, etc). Somewhat less effective on the rear, but I just need to reduce the flow a bit.
So far it has worked perfectly. Haven't had any really cold days yet, but on the cool days I can get temps to >180. When I left Petit Jean, the temps were moderate. I forgot to reopen the shutter before departure, oil temps topped at 200 with the shutter closed during cruise-climb. Dropped back to about 180 as soon as I opened the shutter some. I have run it during hot Texas days without any high oil temperature issues (shutter open).
That would be AWESOME but should pay more than just shipping! I will try to send you a private message to coordinate.
Scott Hersha
Well Known Member
I spoke with Larry Vetterman at length a few years ago about this. Larry had a cockpit controlled ball valve mounted in his oil cooler feed line. He could control it precisely he said. He knew at what oil temp his engine ran the smoothest - something like 192……. He could tell the difference when his oil temp got a little north or south of that optimal temperature, and he could pretty precisely control it to that degree. Seems like an easier solution to some of these oil temperature concerns mentioned in this post, at least after initial installation challenges (running a control cable and then hooking it up to the ball valve lever, installing new length oil lines). You probably have an unused ball valve somewhere.
Sounds like I’m talking myself in to it………
Toobuilder
Well Known Member
I went so far as to buy a shutoff valve and started to mock up the cable. I think its a good solution for control, but in the end I just didnt like the added weight and complexity. My scheme for summer is to add a viscosity valve (which forces all flow through the cooler) and my winter scheme is to remove it (allowing my poor performing vernatherm to sort of do its thing). Its a 10 minute job to swap them out and so far, its good enough for my circumstances.
Using cooler hoses of a smaller diameter is not much like Larry's ball valve setup.
The -6 hose approach retains temperature regulation via vernatherm. There is still flow though the cooler when oil temperature is low (ballpark, below 180F) and the vernatherm passage is open. However, as compared to -8 plumbing, the cold volume through the cooler is reduced, and volume through the open vernatherm port is increased.
Note behavior when hot and the vernatherm port is closed. Recall the system has a positive displacement pump. Measured at the cooler return, there will be increased pressure drop with the smaller hose, but volume will be essentially the same as with -8 hose. The overall result will be a slight HP loss, but there should not be a loss of cooling capacity.
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Scott Hersha
Well Known Member
So it seems like, going with a ball valve to regulate flow through the cooler, you’d be better off removing the vernatherm and installing the viscosity valve, giving you more direct control. Larry said that in his full cold position he still had some opening, so oil would continue to flow through the cooler. Maybe not as much as a cool vernatherm condition bypass.
If I understand this correctly, the viscosity valve pops open with cold oil (high viscosity/pressure) bypassing the cooler. As the OT increases the viscosity valve closes due to lowered viscosity, sending the hotter oil through the cooler. If you are restricting flow through the cooler with a ball valve, it’s like adding another poppet valve that isn’t controlled by the oil viscosity, but by the pilot. Closing off the flow through the cooler increases resistance/pressure, opens the viscosity valve, sending the excess oil through the filter without going through the cooler first, since the oil pump is positive displacement. It seems like that would also consume some horse power. Wouldn’t controlling the efficiency of the oil cooler (regulating airflow through it) be more efficient? That way there would be no back pressure on the crankshaft generated oil pump.
MacCool
Well Known Member
I had the same problem. In the winter with temps at 20F (my personal minimum), I’d get oil temp around 125-130F. Summer temps would get me 135-145F. Last condition inspection (in the spring) I had my A&P install an anti-splat oil shutter on a Bowden cable. Problem solved.
ETA: this is Minnesota. Ambient temps year-round may be different than what y’all might be seeing in some other parts of the country.
What temps do you see now with the oil shutter in place?
Saville
Well Known Member
Source for the "foil tape"
Can anyone supply a source for the "foil tape" used to block off the air to the cooler? Or a description of its properties so that I can buy a roll?
I'm going to put this on the engine side of the baffle, blocking the airflow into the cooler until i get an anti-splat and install it. So I want it to be the right stuff for something in the environment so close to the engine.
Thanks
Can anyone supply a source for the "foil tape" used to block off the air to the cooler? Or a description of its properties so that I can buy a roll?
I'm going to put this on the engine side of the baffle, blocking the airflow into the cooler until i get an anti-splat and install it. So I want it to be the right stuff for something in the environment so close to the engine.
Thanks
It's aluminum foil with an adhesive. Commonly used for sealing ductwork in homes. Lots of discount brands. Suretape AF099 and 3M 3340 are good brand name choices.
MacCool
Well Known Member
Cruise at 3500 feet on a Minnesota summer day with shutter fully closed gets me around 190-200 degrees F. Fully open in the same conditions gets me about 140-150 F. I haven’t flown it this fall (grounded post-op), but that would complete the testing (we have snow on the ground today).
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Saville
Well Known Member
Thanks Dan. I take it that the adhesiive on these brands are long lasting enough so that i don't have to worry about tape falling off and into the engine controls.
AlexPeterson
Well Known Member
We care because, when the oil is colder than something around 130-150F, water vapor in the combustion process is putting water into the oil (some of the exhaust blows by the rings and into the crankcase, condensing into the oil). As the oil warms into the 130-150 range, no net water is being added to the oil. Above something like 150, water will be leaving the oil. The rate at which it leaves the oil will depend on how much above this 130-150 range the oil temperature is. At 160, for example, it will take longer to "dry" the oil than at 180. No magic threshold where all is good.
It is helpful to realize that engine exhaust contains a lot of water - more water comes out the exhaust than the fuel that is burned. Engine exhaust has a dewpoint in the 130-150F range. We've all seen the large amounts of water which drip from a newly started automobile tailpipe. Water keeps condensing inside the exhaust system until it becomes warmer than the dewpoint of the exhaust, at which point it begin to dry out. The oil in your airplane engine is no different.
Thanks Alex. When I get my oil analysis done, it shows no water. Does that mean that I'm getting my oil warm enough? I'm not challenging the fact that a lot of water is produced as part of the combustion process, and a lot of that water ends up in the oil. I'm trying to find data to support a particular oil temperature. Seems the conventional wisdom is around 180F - and conventional wisdom is often correct.
I'd like to understand if there is some actual data to support this temperature recommendation, since my oil runs a lot cooler, and I have no water in my oil (according to Blackstone). If getting oil out is the only reason to increase the oil temp, then I guess I need to take no action. If there are other reasons, then I need to change my oil temp.
I know it's not a perfect analogy, but it used to be conventional wisdom that running LOP would destroy your engine. We now know that's not true.
I've had a strip of the above Suretape sealing the center seam on my firewall insulation for about 1100 hours now.
Most likely because it is the value published by Lycoming. They have to pick something, but there are variables, so there is no perfect pick...
I'm with everything Alex said. Add these factors.
The oil temperature indication we see is not the temperature in all parts of the engine. It's actually the lowest temperature, having just come from the cooler and filter. It's probably 15F or more less than sump temperature, and much lower than (for example) the small quantity of oil draining back from the heads. Further, although 130F oil may condense some water from the blow-by gas, there really is limited contact with that oil pool. The whirlwind of air and aerosol oil droplets in the upper crankcase is somewhat warmer than sump temperature. In my own measurements, breather outflow was typically 15F higher than indicated oil temperature.
The quantity of water being introduced to the crankcase is a function of blow-by. If ring seal is good, there will be less water. If perfect, there would be none. A temperature requirement would thus be variable between different engines.
Cool down after parking in the hangar converts more water to liquid phase than can possibly be condensed while in operation. So, the quantity of water to be converted back to vapor phase (and expelled via the breather) is much higher during the initial run period, as compared to later in an extended run. Short periods of operation need higher oil temperature, while longer flights may be fine with some lower temp.
Airflow question?
I too am in the "it's not quiet hot enough" all the time camp. I, from my angle angle valve days have an 11 row oil cooler mounted on the firewall via an RV-10 mount, fed by a 4 in duct coming off the baffles behind number 4. On normal south Georgia days during climb I could get the temp up to 190 at a slower airspeed even with leaning during the climb....
All's well and I'm not really worried since I fly my plane quiet often.
What I have done is install a plate over the inlet behind number 4 with a 2 inch hole in it.
That did raise the temps a bit but I'm still just about 160 at altitude LOP.
My real question after all this is,
Does the 2 inch opening, feeding into the 4 inch duct all the way to the cooler really do any good, or, once the air is pressurized is it about the same flow through the cooler?
I today with the cooler temps decided to put speed tape over half the hole and I'll report back.
Inquiring minds..
I too am in the "it's not quiet hot enough" all the time camp. I, from my angle angle valve days have an 11 row oil cooler mounted on the firewall via an RV-10 mount, fed by a 4 in duct coming off the baffles behind number 4. On normal south Georgia days during climb I could get the temp up to 190 at a slower airspeed even with leaning during the climb....
All's well and I'm not really worried since I fly my plane quiet often.
What I have done is install a plate over the inlet behind number 4 with a 2 inch hole in it.
That did raise the temps a bit but I'm still just about 160 at altitude LOP.
My real question after all this is,
Does the 2 inch opening, feeding into the 4 inch duct all the way to the cooler really do any good, or, once the air is pressurized is it about the same flow through the cooler?
I today with the cooler temps decided to put speed tape over half the hole and I'll report back.
Inquiring minds..
All very helpful, thanks. Any one ever see a Blackstone report with water in the oil? I wonder if using that as an indicator that I'm doing things right is valid.
BTW, I use an electric engine dryer in the hangar, which might help get out the remaining after-shutdown moisture.
MacCool
Well Known Member
My Blackstone reports all report 0% water. I don't know what that implies. I suspect if there was water, that would be bad.
I use an engine dryer as well 24/7. Don't know if it helps, but it can't hurt, and it was cheap.
RV8JD
Well Known Member
All my Blackstone reports show 0.0% water. I do not use an engine air dryer, but fly fairly frequently. I try to keep the oil temp between 160°F and 205°F, aiming for 180°F to 190°F.
ArlingtonRV
Well Known Member
I too have never had any water reported in my Blackstone oil sample report. I don't have a drier and I fly fairly regularly, though not as often as Carl.
MacCool
Well Known Member
So let me ask this:
If my engine was chronically running too cool, say…130°--140° F indicated on the oil temp gauge…what effect on the engine might I expect to see on borescope and/or oil analysis? Or any other parts of the engine? I realize that the recommended operation oil temp is largely about boiling off the water that accumulates as part of the combustion process, but ultimately, short or long term, what would be the effect on the engine that might result from chronic under-temp operation?
If my engine was chronically running too cool, say…130°--140° F indicated on the oil temp gauge…what effect on the engine might I expect to see on borescope and/or oil analysis? Or any other parts of the engine? I realize that the recommended operation oil temp is largely about boiling off the water that accumulates as part of the combustion process, but ultimately, short or long term, what would be the effect on the engine that might result from chronic under-temp operation?
RV8JD
Well Known Member
Not sure. Note that Lycoming states that the oil temp should not be below 140°F during continuous operation.
Excerpt from the (I)O-360 manual:
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Saville
Well Known Member
foil tape..where and how large?
So I got a roll of the foil tape that was suggested and I need to put some in front of my cooler as the aft cover doesn't get the oil up in temps in the Winter.
The questions are: how much and where?
How wide a strip should I start with? I might start with a 1" wide strip and work up from there (or down if need be).
And where should the strip go? Middle of the height of the cooler? Top? Bottom?
Insight welcomed.
Thanks!
So I got a roll of the foil tape that was suggested and I need to put some in front of my cooler as the aft cover doesn't get the oil up in temps in the Winter.
The questions are: how much and where?
How wide a strip should I start with? I might start with a 1" wide strip and work up from there (or down if need be).
And where should the strip go? Middle of the height of the cooler? Top? Bottom?
Insight welcomed.
Thanks!
I can't answer you directly because my cooler is fed by a 3" Scat tube from the engine baffle. The previous owner (we bought it in Sep) had 2/3 of the 3" engine baffle air inlet hole taped over and suggested we'd want to cover it further for winter flying (that allowed us to get the oil temp up to 155-160 in Fall temps).
In other words - even a small amount of airflow apparently does a lot of cooling. If I were you'd I'd start with 50% covered and take a short flight in the airport area to see the results and adjust in either direction as needed. Unfortunately, removing the upper cowl for each adjustment will be a bit of a pain. Let us know how it goes.
Saville
Well Known Member
Thanks. Will do.
MacCool
Well Known Member
Yeah...I've read that and was the reason I decided to install the oil shutter. At 20° F ambient I was getting 125° - 135° oil temps. The builder and previous owner likely never had to contend with those air temps.
While I recognize that those cool operating temps are bad, I was interested to know why they're bad. I realize that water might not boil off etc, but what damage does it do to the engine and more importantly how might that manifest itself on inspection (as in borescope or oil analysis)?
From my understanding, the only downsides to cool oil are the higher pressures and the slower rate of water removal. Higher pressures are tougher on things, so the manufacturer wants the engine run with designed pressures. This is highly variable in the Lycoming world with the methods used for pressure control. With the regulation methods in a Lyc, cooler temps produce higher oil pressures.
Every engine produces moisture in the crankcase cavity and if the engine is not run long enough or hot enough, that moisture will not be fully removed and will mix with other stuff and create a sludge type product that is corrosive. If that sludge forms on steel parts, they can corrode rapidly, as it is acidic. Used to see this all the time in cars from the 70's that were slow to warm up. Little old lady that only drove to the grocery store has chunks of white sludge under the oil cap. That sludge is formed when moisture particles are present in the oil.
The problem is that we don't know the time/temp relationship to estimate how long of an engine run at a given temp will remove all the moisture that collected after the last shut down, which is also highly variable based upon atmospheric conditions. I am confident that running an engine for 2 hours at 140 OT will remove all moisture, but have no idea at what time point it is gone. I run OT's around 155-160 in winter conditions and I rarely run the engine less than one hour. I have NEVER found any sludge showing that moisture is being retained in the oil and I have seen numerous examples of it in the auto world.
You must remember that the Lyc temp recommendation has to assume you are running straight 60 weight oil, as that is allowed. It is possible that their recommendation is more pressure driven than temp driven.
Moisture is not retained in oil over any extended period of time. An oil analysis with 0 water particles means that the oil did not have moisture at the time of testing. However that doesn't mean it did not have moisture in it at the time it was drained from the engine. The extreme pressure in the oil pump will mix the water with the oil, however, over time, oil and water will separate without an emulsifier.
Larry
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RV8JD
Well Known Member
See Post #28 for a pic. I've done this for many years on two RV-8s with PV 180 HP engines.
