How to keep engine warm when flying in winter

[hoyden]

As winter settles in I'm having a hard time keeping my CHTs and oil temps at the desired temperatures. I installed the Anti-Splat-Aero oil cooler shutter on the firewall side and that helps bring the oil temp above 150F. My CHTs are running between 250-300F.

I am flying an RV-6 with IO-360 and CS prop. I typically fly very LOP, or at peak EGT with power levels between 30-40% except for WOT takeoff to cruise altitude (typically less than 2K AGL). This is flying around the patch missions.

I am considering installing some sort of plate to reduce the cowl opening area. Before starting a science fair experiment I wanted to ask how others keep their temps up on cold days.

[dave_091]

Originally Posted by hoyden

As winter settles in I'm having a hard time keeping my CHTs and oil temps at the desired temperatures. I installed the Anti-Splat-Aero oil cooler shutter on the firewall side and that helps bring the oil temp above 150F. My CHTs are running between 250-300F.

I am flying an RV-6 with IO-360 and CS prop. I typically fly very LOP, or at peak EGT with power levels between 30-40% except for WOT takeoff to cruise altitude (typically less than 2K AGL). This is flying around the patch missions.

I am considering installing some sort of plate to reduce the cowl opening area. Before starting a science fair experiment I wanted to ask how others keep their temps up on cold days.

I’m heading out flying today if it isn’t too cold. It’s now minus 26 Celsius here and if it gets a few degrees warmer I’ll go flying.
I’ll take note of my temps and my flying profile during stages of the flight. I’ll let you know my observations.

[lr172]

Lyc recommends OT no lower than 160. Not sure how big of a deal it is to run at 140 or 150. I suspect that the only issue, assuming a 20w50 oil is used, is that moisture removal from the oil is slower at lower temps. Both of my planes run in the 160 range in the winter months. Doesn't concern me. I know the oil gets less viscous as the temps rise, so it is possible that Lyc thinks that puts more strain on the oil pump. It is likely that they have a good reason for setting this recommendation and therefore good to take steps to get your temps there or close to it. Also possible that it is an issue like running LOP, where they recommend against it, not because it is bad per se, but because of other reasons. I think by now it is safe to say that running LOP on a Lycoming is not bad for the engine, yet they still recommend against it.

I fly a good amount in the winter and often see CHTs in the upper 200's. Too me, this is good not bad, I don't know the low end limit for CHT's, but suspect it is well below 250 and that would be for engine performance, not potential damage or wear. If it were of concern for engine longevity, I am confident that a low end recommendation would be found in the Operators manual, just like the low end for OT. There is no reference.

For decades, planes didn't have CHT instruments. Things seemed to work fine in all different climates.

Larry

[Schooner69]

Hoyden:

Here in the south part of BC (Okanagan Valley), we have pretty reasonable winter temperatures, -5C to -15C on ground.

I have a manufactured 'flapper' on the aft side of the oil cooler and will put a strip of 'gun tape' on the forward side if temperatures dictate.


I put overlapped strips of 'gun tape' on the cowling intakes as required: two initially; more as the season progresses and the temperatures fall.


Cruising at 2300-2400 RPM (FP), I see CHTs of 350 and OTs of 170-180.

Replace the gun tape on the cowl every 3 - 4 weeks; if not, the glue will bake on the cowl and be a bear to get off...

[jrtens]

On my Cirrus I used colored vinyl tape as necessary on the cowl intakes. Stayed on just fine and was easy to remove - no damage to your paint.

https://www.homedepot.com/p/Commerci...5336/206874157

[donaziza]

I'm no mechanic, but I watch a lot of Mike Busch's webinars. (I think everyone knows who he is). Anyway, I "think"? he said, don't run your CHT's below 350*. Reason----lead deposits start to form on your valves, and particularly, the exhaust valve, which of course is not good.
I've got one cylinder running about 320*, and don't know how to get it higher---forget now which one it is til I fly again.

[lr172]

Originally Posted by donaziza

I'm no mechanic, but I watch a lot of Mike Busch's webinars. (I think everyone knows who he is). Anyway, I "think"? he said, don't run your CHT's below 350*. Reason----lead deposits start to form on your valves, and particularly, the exhaust valve, which of course is not good.
I've got one cylinder running about 320*, and don't know how to get it higher---forget now which one it is til I fly again.

I have 800 hours on my 320 in the 6. I fly a lot in the winter with CHTs from 275-325. Checked the exh valves a few hours ago and zero lead deposits on the valves. Need to be cautious with some of Mike's guidance, as it appears to be spit balling and non-fact based assumptions or at least generalization. Lead deposits are all about the combustion and exhaust temps, as well as valve stem temps which don't necessarilly correlate directly with CHTs, as they can have wide swings with the same combustion temps due to air temp and volume / velocity over the fins,

Larry

[hoyden]

I've heard similar; don't run with CHTs below 350. OTOH, I subscribe to Savvy's analysis program and at every update I get kudos for my CHTs:

"Outstanding! The maximum CHTs attained during your flights has been exceptionally low, with a median lower than 80% of the cohort. We think you can expect above-average longevity of your cylinders if you continue operating with your current power settings. Keep doing what you're doing!"

The analysis compares 61 flights between Nov 12, 2020 and Nov 12, 2021, compared with 956 flights by a cohort of 34 RV-6 aircraft.

As a Hail Mary to lead fouling valve stems I run at peak EGT (35% power, 19" map, 1900 rpm) which typically is around 1300. I've run at extreme LOP and low power for more than 5 years. When I'm flying around the patch (southern MN) I'm never in a hurry so I putter along at 100 kts.

One reason for starting to build an RV-9 after flying my RV-6 for more than 20 years is to reap some benefit from the bigger wing and willing to sacrifice some performance for better low and slow flying. Plus I want to build an RV-9 now that I have the space and I want a slider this time.

It's a mystery.

[avrojockey]

Originally Posted by donaziza

I'm no mechanic, but I watch a lot of Mike Busch's webinars. (I think everyone knows who he is). Anyway, I "think"? he said, don't run your CHT's below 350*. Reason----lead deposits start to form on your valves, and particularly, the exhaust valve, which of course is not good.
I've got one cylinder running about 320*, and don't know how to get it higher---forget now which one it is til I fly again.

I love Mike Busch...he has done a lot to advance aviation maintenance and safety, but one needs to take his guidance in context. Maintaining a range of 350-400 in a lyc is impossible in all flight regimes.

Within the greater scope of safety...

• In the pattern, fly the airplane. Knowing the health of your engine is great, but there's too much variability in power to focus on temps. If the airplane is producing normal power...fly it.
• OP mentioned flying very lean...if you're lean, and producing much less than rated power, there's less fuel to generate heat. I fly very lean also, and because I'm not producing much power, my temps are usually between 280-300. Well within Lycoming's recommendations. The lower fuel flow also means less lead for the potential to cause valve deposits. I think we're better served looking outside, commanding our craft and mitigating the valves issues through other means.

I'm in the same camp as Larry...you're ok with those temps.

[rv8ch]

Originally Posted by avrojockey

I love Mike Busch...he has done a lot to advance aviation maintenance and safety, but one needs to take his guidance in context. Maintaining a range of 350-400 in a lyc is impossible in all flight regimes.

...

I also wonder if he would change his guidance if running unleaded, since the reason for the higher temps is to avoid lead deposits.