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How to keep engine warm when flying in winter

Ref: https://www.avweb.com/features/avwe...-65where-should-i-run-my-enginepart-3-cruise/

Pelican’s Perch #65: Where Should I Run My Engine? (Part 3 – Cruise)
Cruise -- Time to sit back and enjoy the flight. But wait ... did you leave the mixture set where it was during the climb? Or do you just set it where it

John DeakinFebruary 2, 20030




At this point, the question usually comes up about “minimum CHT.” We know of no data to support a minimum CHT. The only evidence I can find is that many of the manuals for the old radials had a note (not a limit) that said, “Do not take off with CHT less than 100°C,” which is about 212°F. Modern liquid-cooled TCM engines have the thermostat set for 240°F. That seems pretty reasonable to me.
 
center blockage

previously I tried blocking the cowl inlet edges but my CHT's did not remain even so I put the blockage in the middle. that keeps my CHT's even. in a climb you have some air going over the top of the post but less so for cruise so that allows for a wider range of outside air temps for operation.

42b789_c865a71967cb443a904dbb2b122ba732~mv2.webp
 
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previously I tried blocking the cowl inlet edges but my CHT's did not remain even so I put the blockage in the middle. that keeps my CHT's even. in a climb you have some air going over the top of the post but less so for cruise so that allows for a wider range of outside air temps for operation.

42b789_c865a71967cb443a904dbb2b122ba732~mv2.webp

Steve, any CHT numbers associated with the mod?

Also, have you ever tried printing anything to restrict outlet area?
 
Steve, any CHT numbers associated with the mod?

Also, have you ever tried printing anything to restrict outlet area?

I have posted some numbers from time to time. if you restrict the exit, the cooling distribution may be affected, by how much I don't know. in general, it is always better to meter the upstream cooling entrance and let the air distribute thru the cooling fins. in this case the inlet (flow meter) is close coupled with the engine cooling fins and that in itself affects the cooling distribution.
 
I have posted some numbers from time to time. if you restrict the exit, the cooling distribution may be affected, by how much I don't know. in general, it is always better to meter the upstream cooling entrance and let the air distribute thru the cooling fins. in this case the inlet (flow meter) is close coupled with the engine cooling fins and that in itself affects the cooling distribution.

Thanks. I’ll see what I can find in a search.
 
OIL TEMP is critical.... 165F is a minimum. 220f is max but I like 190'ish max.

CHT from Lycoming Engine Manual

At Bayonet Location For maximum service life of the engine maintain cylinder head temperature between 150°F and 400°F during continuous operation.

So CHT 150F Min with the OT limit 165F Min. I will say 400F is sporty for max continuous CHT for me. I like to see something less like 350F give or take 20F.

As other posted cowl inlet blockers will help. I never had to do that but I have in the past partially block oil cooler in winter to keep OT warmer.
 
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Not the most elegant of solutions but allows me to continue flying as the temperatures drop. I also added a small piece of tape 1”x3” over the oil cooler. The tape is “high speed” from airline mechanic friend that they use commercially. I’m planning to build fiberglass inserts during my annual in Jan.

Data: 3500’ ASL OAT -5 C 2300rpm 23” leaned to peak

Pre-tape: Cyl 310/325/285/275 oil 175F
Post-tape: Cyl 330/340/310/305 oil 192F

p35SC4g-0%21sizeoriginal-M.jpg
 
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Quoted from Walter Atkinson...Gami injectors person, amongst a host of other experience on many types


"A couple of things to remember:

Lycoming publishes a min operating CHT of 150dF. TCM has not published a min CHT, but set the liquid cooled CHT to run at 240dF. Reading between the lines in TCM’s writings suggests that anything above 200dF is acceptable.

TCM data on oil temp from Bob Mosely (RIP) suggests 180-190 for one hour gets rid of the water. Consider that the oil (water in the oil) is hitting the under side of pistons and cylinder walls which are above the boiling point of water and being vaporized.

As for runup, based on above and a hundred years of experience in all forms of aviation engines and data from multiple engine manufacturers oil temp should be above 90dF (some radial recommendations are 100dF) and CHTs above 200dF. Based on Lycoming’s min CHT above, 150dF should be enough. FWIW, my personal rules are 90 on oil and 200 on CHT.

Some of this might be altered with different oil weights and multi-vis stuff. I know of no hard data breaking all of that down.

_________________
Walter Atkinson "

I worry most about differential expansion rates of piston and cylinder and the scuffing it can cause, so I set a min CHT of 250F for T/O. If the engine was warm to begin with, I wouldn't worry. I use 20w50 and completely disregard OT, though It is rarely below 75-80 after getting the CHTs to 250. I use an oil sump heater when temps are below 35-40. If I was using 40 or 50 wt oil, I would probably have a min OT for full power.

Larry
 
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Quoted from Walter Atkinson...Gami injectors person, amongst a host of other experience on many types


"A couple of things to remember:

Lycoming publishes a min operating CHT of 150dF. TCM has not published a min CHT, but set the liquid cooled CHT to run at 240dF. Reading between the lines in TCM’s writings suggests that anything above 200dF is acceptable.

TCM data on oil temp from Bob Mosely (RIP) suggests 180-190 for one hour gets rid of the water. Consider that the oil (water in the oil) is hitting the under side of pistons and cylinder walls which are above the boiling point of water and being vaporized.

As for runup, based on above and a hundred years of experience in all forms of aviation engines and data from multiple engine manufacturers oil temp should be above 90dF (some radial recommendations are 100dF) and CHTs above 200dF. Based on Lycoming’s min CHT above, 150dF should be enough. FWIW, my personal rules are 90 on oil and 200 on CHT.

Some of this might be altered with different oil weights and multi-vis stuff. I know of no hard data breaking all of that down.

_________________
Walter Atkinson "

Reading your post reminded me of Walt. I’d like to give that fine man a RIP also. Unfortunately, our community lost Walt last year.
 
Tape

Gaffers tape is a great alternative to duct tape. I've used it for blocking my inlets before with good results. It's much stronger than painters tape and leaves minimal residue. Any residue left is easily cleaned off. Downside is that it's pricey.
 
I am learning from this thread. I have been going over my flight data and seeing my oil temp is not going over 135 though my cylinder temps are in the 370-400 range and exhaust temps up to 1480 at peak, mostly around 1400.

I preheat my engine overnight like this photo and I get the oil to about 75 and the carb to about 90.

I can see the oil needs to get hotter but my exhaust temp is as high as I want it to go. My thought is to cover part of the oil cooler or plug the blast tube on it but I dont want the other temps to go up.

Am I over focused on the exhaust temp?
 

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rockwood: place your EGT probes 2" lower on the exhaust pipes to solve your high exhaust temp problem.:D

your CHT's and Oil temps matter, EGT's shouldn't.
 
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I am ok in the pre heat but having trouble getting the oil up to temp in flight. After an hour flight the max the oil got was 131degrees. My plan is to put aluminum tape over the outside of the oil cooler. I’m sure putting it on the inside of the plenum would be better but thought I would try this first. Is there a reason to not try this? I tried taping the front of the plenum holes 1/3 and it increased the CHT but did nothing for the oil. Any thoughts?
 

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I am ok in the pre heat but having trouble getting the oil up to temp in flight. After an hour flight the max the oil got was 131degrees. My plan is to put aluminum tape over the outside of the oil cooler. I’m sure putting it on the inside of the plenum would be better but thought I would try this first. Is there a reason to not try this? I tried taping the front of the plenum holes 1/3 and it increased the CHT but did nothing for the oil. Any thoughts?

With exhaust gas temperature, I think what matters is not the actual number but the trend. I've been told that using EGT for anything other than finding the peak temp and adjusting mixture rich or lean from there is the not very useful.
 
With exhaust gas temperature, I think what matters is not the actual number but the trend. I've been told that using EGT for anything other than finding the peak temp and adjusting mixture rich or lean from there is the not very useful.

Thanks. I agree - Im not to worried about the exhaust gas temp but I want to make sure I can keep the oil temp high enough. I hoped putting the tape on the outside of the oil cooler would help so I didnt have to take off the plenum to cover the inside.

You are in cold town USA so how do you keep your engine oil hot enough? Im having trouble betting to 120-130.
 
I am ok in the pre heat but having trouble getting the oil up to temp in flight. After an hour flight the max the oil got was 131degrees. My plan is to put aluminum tape over the outside of the oil cooler. I’m sure putting it on the inside of the plenum would be better but thought I would try this first. Is there a reason to not try this? I tried taping the front of the plenum holes 1/3 and it increased the CHT but did nothing for the oil. Any thoughts?

Get that nice plenum off and tape inside the cooler. Completely. You would be pleasantly surprised what it does. When it's very cold tape both sides.

Tape at the back as shown will eventually peel off due to a lot of air pushing on it.
 
I agree with Vlad. I have a cable actuated shutter on the front of the cooler and this time of year it is almost completely shut all the time.
 
As a reference: I have a good cowled airplane and always have cool - cold CHT. I tape almost 100% of the cooler almost all winter. Live in the Chicago area. I fly south just N of Atlanta before I stop for fuel, and I take the tape off then.
 
In the past years I would tape over about half the cooler but last year I taped over the entire cooler. It did help to warm the oil up faster and hotter but to the point that I had to pull the power back so much the CHT's stayed cooler than I would have liked.
Just outside of the Detroit area.
 
New Rv8 owner here. I am dealing with same issue with my 8. Faster I go the colder my oil gets. Cylinders too.
I have not installed oil cooler flapper door yet. What kind of tape are you using? My cylinders were around 230. Too chilly
 
I have the Anti-Splat-Aero oil cooler shutter on the firewall side, and I've fully covered the front side with aluminum tape. I have 2" vertical strip of painters tape centered over each cowl inlet. With OAT 17-35F I typically get cruise oil temp 165F and CHT 270-300F. WOT takeoff oil temp 185F and CHT 350F.
 
here comes just another data point: i recently installed the vans shutter on my oil cooler due to persistent low oil temps. actuated via bowden cable from cockpit.

i saw a delta of around 20 F between fully open and closed. good enough for me. i found it remarkable that it really takes a while for the oil temperature to reach it's upper/lower limits, 5 - 10 minutes or so.

btw... i saw a drop of CHT's across the board by around 5 F when closing the shutter.
 
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Just landed…

Attached is the picture of my “duct tape” mod.

I flew today and here are my notes:

Weather : -25 degrees Celsius, sunny, no winds (beautiful day)
Oil temp throughout flight: 175 - 185 F
CHT’s: 360 - 385

I’m very happy with the mod 🙂
Easy to implement and it will be easy to remove with some gunk remover.
 

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Nice pic and nice temps, Dave. I'm shivering just looking at it. I have one 2" strip of tape in the center and considering adding another inboard.

Have you explored the maximum uppers temps before too much of a good thing is not wonderful?
 
Nice pic and nice temps, Dave. I'm shivering just looking at it. I have one 2" strip of tape in the center and considering adding another inboard.

Have you explored the maximum uppers temps before too much of a good thing is not wonderful?

This was my first time adding tape. I think I nailed it for these temperatures.

I flew two weeks ago in the same OAT and my oil temps were quite low, it was hard to keep my oil above 130.

Here is another pic after I rolled in and shut down. Looks like a sunset picture but it was taken at 1230 in the afternoon. The joys of subarctic winters!

My iPhone shutdown after the photo was taken because it was too cold for it to work properly.

On a side note, it’s pretty hard to fly with all the winter gear I have on. Especially two pairs of thick socks inside huge insulated winter boots. I really have to ensure I don’t snag anything in the cockpit.
 

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Oil Cooler Tape follow up

I have a flight today. It was about 30 degrees. Since I still had the top of the cowl off I had to decide if I wanted to take the plenum off to tape the oil cooler from the inside or just tape the back. It was cold so I took the easy way and taped the full backside between the baffles and firewall.

I went from a high of 128 last flight to 154 today. The CHT were all fine - in the 340-385. My EHT are still pretty high getting up to 1515 but mostly stayed about 1385.

My plan is to order an oil cooler shutter from Alan or Vans - not sure what one to get. The plenum as good as it works is a pain to take on and off and Im sure a shutter would work better. Taping the front inlets raised the CHT but did nothing or very little to the oil temp so that is why I tried taping the oil cooler.

I love the data log from the G3x. It is fun looking at the numbers. Today I got to 192.8 knots groundspeed. Going the other direction wasnt as fast!
 
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I have a flight today. It was about 30 degrees. Since I still had the top of the cowl off I had to decide if I wanted to take the plenum off to tape the oil cooler from the inside or just tape the back. It was cold so I took the easy way and taped the full backside between the baffles and firewall.

I went from a high of 128 last flight to 154 today. The CHT were all fine - in the 340-385. My EHT are still pretty high getting up to 1515 but mostly stayed about 1385.

My plan is to order an oil cooler shutter from Alan or Vans - not sure what one to get. The plenum as good as it works is a pain to take on and off and Im sure a shutter would work better. Taping the front inlets raised the CHT but did nothing or very little to the oil temp so that is why I tried taping the oil cooler.

I love the data log from the G3x. It is fun looking at the numbers. Today I got to 192.8 knots groundspeed. Going the other direction wasnt as fast!

I have heard both shutters are good products (personally I have Anti splats) but just a heads up, Van's orders are significantly delayed right now. May be worth a call to Alan to see how quick they can get you one.
 
I recommend the following modifications to resolve low temps in winter operations.

First: loose the LOP
Second: Whats up with 30-40% power? run it at 65-75%

No additional mods required.

The problems you are causing yourself far outweigh the little bit of fuel you think you're saving.
 
I am ok in the pre heat but having trouble getting the oil up to temp in flight. After an hour flight the max the oil got was 131degrees. My plan is to put aluminum tape over the outside of the oil cooler. I’m sure putting it on the inside of the plenum would be better but thought I would try this first. Is there a reason to not try this? I tried taping the front of the plenum holes 1/3 and it increased the CHT but did nothing for the oil. Any thoughts?

On my -9 (sold), I made an aluminium plate covering the entire back of the cooler attached with 2 an bolts. The -9 being tight cowl, no air restriction needed to maintain cyl. temp. Did the job up to -20F.

Michel
 
I am ok in the pre heat but having trouble getting the oil up to temp in flight. After an hour flight the max the oil got was 131degrees. My plan is to put aluminum tape over the outside of the oil cooler. I’m sure putting it on the inside of the plenum would be better but thought I would try this first. Is there a reason to not try this? I tried taping the front of the plenum holes 1/3 and it increased the CHT but did nothing for the oil. Any thoughts?

On my -9 (sold), I made an aluminium plate covering the entire back of the cooler attached with 2 an bolts. The -9 being tight cowl, no air restriction needed to maintain cyl. temp. Did the job down to -20F.

Michel
 
The oil cooler blocking plates for the O-360 in my RV6. One for winter and one for summer. Just installed the winter plate this morning. Been doing the job for 25 years now.

IMG_0758.jpg
 
I taped the inside of the oil cooler today and was able to reach 168 degrees for the oil temp. CHT's still all below 390. I ordered the shutter from Antisplat and will install it when it comes. With it, I think I can get the temps up to where they need to be.
 
Winter flying over the rockies in Colorado ifr minimums is 15500 and oat temps usually 20 degrees and lower. With overcast skies running low egts and chts make for very little cockpit heater output. Problem with putting tape over the inlet air and or the oil cooler is that where you are goinging might be a lot warmer than where you started. Keeping your engine operating at steady temps 350 to 400 cht and 1300 to 1400 egt and 180 to 210 oil temp is optimal for engine longevity and good heater output. That being said what i did was install an cable operated oil door and a cable operated flap mounted to the lower firewall flange (so I wouldn't have to disconnect it when I removed the cowl) on the exit air in between the exhaust stacks. The only problem with this set up was that it disrupted the exit air when it was open in the summer. So I drilled 3- 3/4 HOLES in the flap and that solved the problem. Now no matter how cold the oat is I can run within the parameter stated above and the heater works as intended.
 
...what i did was install ... a cable operated flap mounted to the lower firewall flange (so I wouldn't have to disconnect it when I removed the cowl) on the exit air in between the exhaust stacks. The only problem with this set up was that it disrupted the exit air when it was open in the summer. So I drilled 3- 3/4 HOLES in the flap and that solved the problem. Now no matter how cold the oat is I can run within the parameter stated above and the heater works as intended.
Any chance you could post a picture of your firewall flap setup?
 
AntiSplat Shutter

I ordered my AntiSplat shutter on Saturday and got it today. I didnt even pay for fast shipping but once again I have been over satisfied with what I have purchased from them.

The shutter is more solid than I expected and Im sure it will work great. I will post a pic once I get it installed. If anyone has a picture they want to post how they installed it, that would be great.
 
Winter flying over the rockies in Colorado ifr minimums is 15500 and oat temps usually 20 degrees and lower. With overcast skies running low egts and chts make for very little cockpit heater output. Problem with putting tape over the inlet air and or the oil cooler is that where you are goinging might be a lot warmer than where you started. Keeping your engine operating at steady temps 350 to 400 cht and 1300 to 1400 egt and 180 to 210 oil temp is optimal for engine longevity and good heater output. That being said what i did was install an cable operated oil door and a cable operated flap mounted to the lower firewall flange (so I wouldn't have to disconnect it when I removed the cowl) on the exit air in between the exhaust stacks. The only problem with this set up was that it disrupted the exit air when it was open in the summer. So I drilled 3- 3/4 HOLES in the flap and that solved the problem. Now no matter how cold the oat is I can run within the parameter stated above and the heater works as intended.

I too would really like to see pictures of this! I have had a similar thought.
 
I ordered my AntiSplat shutter on Saturday and got it today. I didnt even pay for fast shipping but once again I have been over satisfied with what I have purchased from them.

The shutter is more solid than I expected and Im sure it will work great. I will post a pic once I get it installed. If anyone has a picture they want to post how they installed it, that would be great.

I look forward to the picture. I have that Anti-splat oil cooler on order, along with the Bowden Cable kit and fittings. Are you installing it on the outside, or inside of the oil cooler?
 
I look forward to the picture. I have that Anti-splat oil cooler on order, along with the Bowden Cable kit and fittings. Are you installing it on the outside, or inside of the oil cooler?

When I looked before mine was delivered today, it looked like on the outside would be the easiest and less issues bringing the cable to the needed location. I think it will work better on the outside since it will keep all the heat in and not allow the moving air between the baffles and firewall cool the oil as much.

It has been too windy for me - Im a wuss when it comes to flying in bumps so I didnt go to the airport today. I will have some time tomorrow and see what it looks like.
 
I look forward to the picture. I have that Anti-splat oil cooler on order, along with the Bowden Cable kit and fittings. Are you installing it on the outside, or inside of the oil cooler?

When I looked before mine was delivered today, it looked like on the outside would be the easiest and less issues bringing the cable to the needed location. I think it will work better on the outside since it will keep all the heat in and not allow the moving air between the baffles and firewall cool the oil as much.

It has been too windy for me - Im a wuss when it comes to flying in bumps so I didnt go to the airport today. I will have some time tomorrow and see what it looks like.

I definitely wouldn't put it aft of the oil cooler. People have tried it before and there is still enough air circulation on the oil cooler that you won't be able to get the oil to 180 if it is on the back. Unfortunately if you want it to work right it has to go between the cooler and the baffle.

I suppose on the back side it would certainly be better than nothing but I seem to recall a thread awhile back where even then people couldn't get it above 180. Below is what mine looks like for reference. Gaps have since been sealed and the cable bent for security.
 

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Blocking outlet vs. inlet?

Would it not be better to block the outlet flow rather than the inlet because that would result in a higher pressure inside the cowl and especially above the engine to give more delta P to work with for flow to the cabin?
 
I placed my Anti-Splat oil cooler shutter aft because it was easier to install there. That location helped raise oil temps from 150 to 160F. Then I completely covered the front side with aluminum tape and temps are up to 170. I will need to collect more data before deciding to move the shutter to the front.
 
I placed my Anti-Splat oil cooler shutter aft because it was easier to install there. That location helped raise oil temps from 150 to 160F. Then I completely covered the front side with aluminum tape and temps are up to 170. I will need to collect more data before deciding to move the shutter to the front.

Leave it there. Continue covering the front or put the second shutter :)
 
I definitely wouldn't put it aft of the oil cooler. People have tried it before and there is still enough air circulation on the oil cooler that you won't be able to get the oil to 180 if it is on the back. Unfortunately if you want it to work right it has to go between the cooler and the baffle.

I suppose on the back side it would certainly be better than nothing but I seem to recall a thread awhile back where even then people couldn't get it above 180. Below is what mine looks like for reference. Gaps have since been sealed and the cable bent for security.

Nice. How did you get it through the firewall? What kind of fitting?
 
I used some of these guys from Spruce for all cables through my firewall. There are cheaper ways to get it done that I have seen on the forum but require a little bit of fabrication.

I saw those and I like that concept, but I was thinking more about ease of retrofit installation in a flying RV. I hate crawling under that panel.

How big a hole in the firewall do those eyeballs require? What’s involved in pulling off the oil cooler to place the shutters? Any gotchas?

The list of little projects I want to do during my upcoming condition inspection is getting long.
 
I saw those and I like that concept, but I was thinking more about ease of retrofit installation in a flying RV. I hate crawling under that panel.

How big a hole in the firewall do those eyeballs require? What’s involved in pulling off the oil cooler to place the shutters? Any gotchas?

The list of little projects I want to do during my upcoming condition inspection is getting long.

Ya if panel diving isn't your favorite you may want to look up some alternative options. I think just about anything is going to need some amount of panel diving but these more so. The big hole is 1.125" diameter with six screw holes around it. I needed to use a die grinder with a burring bit to remove material; that stainless steel is some tough stuff.

As far as the oil cooler goes you will have to mark the holes and drill the shutter. Longer bolts will certainly be required. The only gotcha I can think of is to take a look at the oil cooler versus engine mount and see if it were moved aft about 1/4" will it interfere with the engine mount tube. I had to remove some of the flange on the oil cooler to get it to clear the mount and even then it is close.

I can't speak for others but when that shutter is closed on my engine I can get oil temps up to 190-200 on a 20 degree day. While flying I barely have to open it to keep my temps at 180.

Hope this helps.
 
Nice. How did you get it through the firewall? What kind of fitting?
Cheap and effective idea from Sport Avation good for cables such as carb heat or in this case oil cooler shutter. Just drill a 3/16 hole lengthwise through a bolt of sufficient diameter (maybe 1/2?). Drill hole through firewall, add a couple large area washers and locknut. After cable situated fill in any (very minor) voids with your sealant of choice. Done.
 
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