Open cowl vents?

[Cardiff Kook]

My plane has open cowl slots on bottom of engine- both sides. No option to close them.

Is that normal standard? Wondering if not if they should be closed up when temps are below freezing to speed up engine warm up. Need to pay closer attention to low end oil temps while I am up there.

 

[stewartb]

If oil temps aren’t getting up to 180° in flight? Cover part of the oil cooler with duct tape. You shouldn’t need to do anything else.

 

[skywagon8a]

My plane has open cowl slots on bottom of engine- both sides. No option to close them.

Is that normal standard? Wondering if not if they should be closed up when temps are below freezing to speed up engine warm up. Need to pay closer attention to low end oil temps while I am up there.

Do you have a cylinder head temperature CHT instrument? If yes, cover those two outlets and monitor the CHT. As long as it stays below 400F you're safe. This would be like other airplanes which have controllable cowl flaps for this same purpose.

 

[DENNY]

I agree with skywagon, unless you have a 4 cylinder EGT/CHT do not start messing with you cowling inlet or outlet. Adjust the air flow through the oil cooler. Not over you cylinders. Your thinking too hard go fly more. :lol:
DENNY

 

[aeroaddict]

My $0.02. On my plane you can adjust the cowl vents (manual, can't adjust in flight). I have found it didn't make any difference (yes I have full engine monitoring). More effective for oil temps, as stated, is taping off the oil cooler.

And what DENNY said; you're thinking too hard, go fly more.

 

[fobjob]

By my experiments, the bottom vents reduce CHT by 5 deg F each.

 

[BC12D-4-85]

Put an inflight adjustable shutter on the oil cooler to fuss with oil temps. I made my own for a PA-18 but they are commercially available.

Gary

 

[Dog]

I have plates to block them of for real cold weather operation. And 1/3 of the oil cooler taped off works fine from just bellow freezing if it gets much colder than - 20 I tape of the cooler about 50%. Always use the oil cooler tape to get the boil temp up to about 180 in a climb to oil of water that is the main issue moisture =corrosion in your engine.

 

[stewartb]

Are your CHTs low enough to worry about it? My winter CHTs haven’t been. Even when well below zero.

 

[Dog]

Yes they are definitely low - in a hard climb for 5 minutes I can get them to 350 max in cruise around 300-320 at-10 to-20 that is if I keep the oil cooler taped to run 150 to 180

I also have the trust line mod that opens up the bottom of the cowl by about 1.5 inches that keeps her running colder as well.

I prefer to close off the bottom of the cowl to get max upper deck pressure for extra airflow and heat on my rear seat heater.

 

[Cardiff Kook]

If oil temps aren’t getting up to 180° in flight? Cover part of the oil cooler with duct tape. You shouldn’t need to do anything else.

Watched my oil temps today more closely. It was pretty warm out. My guess is 45F on the ground and I was at 1000 feet agl.

My oil temps hovered around 143 during my flight. Thats on a pretty warm day. Engine manual says do not operate continuous if under 140F. If it was 20F colder i cant imagine those temps would have been over 140F.

It certainly never approached the targeted 180F.

 

[stewartb]

Duct tape. I use tape on my 180 even in summer. More in winter. My Cub has adjustable oil cooler air but it tends to run warm so I don’t close them. Every plane is different. To that point I’ve never had CHTs that made me want to mess with things. When I was a new owner I bought a winter front kit for the 180. I used it for about 20 minutes and had to land to remove it. I’m not a fan of limiting flow the cylinders.

 

[Cardiff Kook]

Am I looking for something like this? Will have to see where it is next time I am at plane.

Regular old duct tape across the front? Wont melt? Maybe do 1/3rd to start?

 

[DENNY]

Looks like you have a front mounted oil cooler from a previous post I looked up. It is right below the prop on the nose. 1 inch of tape applied horizontal is usually good for 20 degree change in oil temp. I prefer the aluminized duct tape because it does not leave the sticky mess that regular duct tape does. Start with one inch, go fly, add tape as needed. We should have mentioned that when you first started talking about trying to block off cowling exit I just figured you had already tried to block off the oil cooler air flow.
DENNY

 

[stewartb]

Regular old duct tape across the front? Wont melt? Maybe do 1/3rd to start?

I used regular fabric duct tape for 20 years. It works great. Right now I have aluminum tape on since I had it out. I was using it to tape off cylinder fins to balance CHTs.

Sure, start with a quarter or third of the cooler covered and see how it affects oil temp. I keep my Cessna cooler partially covered in summer. Almost fully covered in winter. My Cub needs all the oil cooling I can give it. Every plane’s different.

 

[Cardiff Kook]

Do you cover all sides, or just block off the front? Of an inch or two of course…

And does it matter what side? I imagine outflow side is better- but not sure what side that is.

 

[mvivion]

Do you cover all sides, or just block off the front? Of an inch or two of course…

And does it matter what side? I imagine outflow side is better- but not sure what side that is.

Nope, tape on front. Tape the back it’ll likely come off….not much grip on those fins.

MTV

 

[Dog]

And make sure to go all the way across the bottom that way the oil will always be able to flow through this part of the cooler thats taped of. So the cooler has a cold and warm, side back when we were using straight weight oil the coolers would clog with with cold oil. The oil temp would go way up then once it pushed through the cooler drop like a hammer.
It is a much more even oil temp if you cover complete length of the cooler part way up.

 

[Kid Durango]

My mechanic said in extreme cold it was best to tape the center of the fins leaving the top and bottom open for the very reason Dog mentioned, the congealing. Made sense to me.

 

[stewartb]

With a rear baffle mounted cooler I taped the back side because it was easier to reach. It worked fine. With a nose mounted cooler I tape the front. Since my Cessna’s (non congealing) cooler has a diagonal bar on the face, I’ve always taped diagonally with the bar. Never any problem. covering the non-congealing row on a Cessna cooler makes no difference in temps. Piper coolers that I’ve had don’t use the non-congealing row.

This pic shows my Cessna’s summer tape. I add more in winter. My Cub has pilot controlled air ducts for the oil coolers. The experimental advantage.

 

[CenterHillAg]

I’ve got an adjustable oil cooler shutter on my Husky, it works great. I’ll pull it completely shut on cold days for warmup and takeoff, then open it as needed while flying. I try to keep the oil temps between 190-205, and it does that easily. Cylinder temp will be around 340 at 24 squared at the same time.

 

[DENNY]

Simple way is start at bottom with one inch strip. Add overlapping 1 in strips until the oil get to the temp you want. As Spring rolls around just remove one inch strip at a time as it gets warmer. Next fall start with it all over again. Leave a little tap at one side of the tape so it is easy to drag and pull off. Normal airflow helps hold the tape in front KISS.
DENNY

 

[Cardiff Kook]

I started from top- didnt see any real change in temps. Hovering under 140F on at -8C

Does top vs bottom matter?

I guess i should just add more?

 

[Cardiff Kook]

Added more…. Maybe a bit too much….

Will temps slowly creep up when adding?

 

[stewartb]

It shouldn’t matter top or bottom. You’re just reducing cooling area. Try more tape. Are you confident that your gauge is accurate?

FWIW, I know guys with 100% covered.

 

[Cardiff Kook]

I know its as accuracy as well as i do in any engine i have ever had a temp gauge on- which is to say not really.

It certainly seems reasonable when the engine is off

 

[55-PA18A]

Since your original concern was low oil temp, you might want to ensure you actually are getting an accurate reading on your oil temp gauge. Test the probe in known temp hot water (ie use an another thermometer). Do a search on this forum for a better description.

Jim

 

[DENNY]

Every plane is different but in general the temps will increase in proportion to amount of cooler blocked off. You may very well be able to block off the entire cooler in colder temps. I have a plate blocking off most all of my rear mounted cooler in the winter. Denny

 

[stewartb]

Cardiff, you’re looking for 180°, so you have a 60° buffer between your goal and OH CRAP. That’s plenty of margin to get down and remove some tape when it passes your comfort zone, which for me is 220°. When my oil has gotten that hot, the smell of hot is more powerful than the gauge. Relax and fly it with incrementally more tape until you hit 180°, abd pay attention to how much tape made how much change so you’ll know how to adjust in the future.

 

[JohnnyR]

This.
If not willing to do cooler shutter, try this 5.9 mil tape. Heavy duty, lasts all season, and won’t deposit adhesive into the fins like some duct tapes.
https://www.amazon.com/gp/product/B07P9J3QQD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

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I’ve got an adjustable oil cooler shutter on my Husky, it works great. I’ll pull it completely shut on cold days for warmup and takeoff, then open it as needed while flying. I try to keep the oil temps between 190-205, and it does that easily. Cylinder temp will be around 340 at 24 squared at the same time.