What is acceptable cht temp in summer?

[Will.iam]

As this will be my first summer with the 252, what are the normal limits we should see climbing out at 120? I saw yesterday with the surface temp of 82dF at the airport, 389 on #3 cyl as the hottest cyl.  Climbing out. i lowered the nose and got up to 130 to climb and it settled down at 382. I noticed a temperature inversion as my outside temp gauge was reading approx 28dC at 5k ft. I leveled off at 7.5k and setup for lop where the temperatures settled at 345 - 310 range. This isn’t even summer temps yet so just wanting to know if this seems high or normal. I only found a thread about temps in the carburetor M20C and how trying to keep them under 400dF was a struggle and normal for that model. Just wanting to hear what is M20K drivers numbers to see if i have a baffle issue. My baffles look pretty new, will have to get a picture on here when I’m out there again. I look for 23-24 fuel flow and i was getting 23.6 on last takeoff interesting that passing through 5k the ff was down to 22.5 i would think with the manifold staying steady at 36” the ff would not change but then with the temp inversion maybe the air was just hotter or maybe i have a problem?

[irishpilot]

Most folk will try to stay under 400 on climb and most would like to see mid-350s at cruise. With good baffling and cowls full open, most can stay at 375 or lower at cruise climb 120 knots. When I bought my Mooney, the baffling looked good, but there were several small problems that added up to higher CHTs. Be methodical in your approach and you'll get them in line. This forum is a great resource!

[LANCECASPER]

5 hours ago, Will.iam said:

As this will be my first summer with the 252, what are the normal limits we should see climbing out at 120? I saw yesterday with the surface temp of 82dF at the airport, 389 on #3 cyl as the hottest cyl.  Climbing out. i lowered the nose and got up to 130 to climb and it settled down at 382. I noticed a temperature inversion as my outside temp gauge was reading approx 28dC at 5k ft. I leveled off at 7.5k and setup for lop where the temperatures settled at 345 - 310 range. This isn’t even summer temps yet so just wanting to know if this seems high or normal. I only found a thread about temps in the carburetor M20C and how trying to keep them under 400dF was a struggle and normal for that model. Just wanting to hear what is M20K drivers numbers to see if i have a baffle issue. My baffles look pretty new, will have to get a picture on here when I’m out there again. I look for 23-24 fuel flow and i was getting 23.6 on last takeoff interesting that passing through 5k the ff was down to 22.5 i would think with the manifold staying steady at 36” the ff would not change but then with the temp inversion maybe the air was just hotter or maybe i have a problem?

First thing I would check is engine baffle seals. Most of them are neglected and are worn out. They blow back under pressure and let air over the top and out the back of the engine rather that forcing the air down over the fins. The infinitely adjustable cowl flaps on your K model (and the M also) cn help keep things cool, and are useful even with good baffle seals.

I bought an Encore in 2014 and on the pre-buy this is what the baffle seals looked like.

No wonder after only 750 hours TT he had to replace the cylinders.

@GEE-BEE Guy Ginbey makes a set of die-cut baffle seals to fit your 252. It was the first thing I did after buying this airplane. I also did it on the airplane I have now, an M model. It makes a huge difference.

[WilliamR]

I see up to about 330-340 on the hottest cylinder on a 252 at all temps and alts. on the climb.  Usually climb out at 115-120 kts indicated.  FF of 22.5 is a bit light.  But it should not change based on altitude assuming all else equal.

 

William

[KLRDMD]

If I see 380º at any time during the flight I do *something* to reduce it. There are many options, of course.

[carusoam]

There is a graph from one of the cylinder manufactures....

Of strength vs metal temp....

Showing a line at 380°F and below...  where the strength is good and pretty even throughout the lower temp range....

Above the line the strength starts to fade away with the temp... good strength, but increased wear can occur...

Above the redline, the strength is still there... but the associated wear is very high...

 

Spring, summer, winter or fall.... 380°F and below for cruise...

In the climb stay as close to 380°F as practical...  2-300 °F ROP... (norm for Continental blue box EGT gauge, or white box on the G1000...)

Guides that work for most piston driven engines...

PP thoughts only, not a flight engineer...

Best regards,

-a-

[FlyingDude]

Hi,

Is there anything like "too low temperatures also lead to wear"? Is it e thing? 

Thanks

[Will.iam]

2 hours ago, FlyingDude said:

Hi,

Is there anything like "too low temperatures also lead to wear"? Is it e thing? 

Thanks

Yes. Mike bush videos talk about too low a cht and the broine chemical reaction doesn’t happen fully and thus you start getting lead deposits IIRC. 

[Warren]

Mike Busch recommends (for Continentals) to keep operating temperatures below 380 for normal conditions and if it starts getting over 380, do something, cowl flaps, adjust fuel flow, reduce power,... do whatever it takes to get back to or below 380.  His recommendation is that at or below 380 the engine will be happy and have a long life.

Mike does say that up to 400 during climb is acceptable but far better to increase airspeed and trade for a lower climb rate to keep temperatures down.

For Lycoming, add 20 degrees to the above numbers — they have liquid filled valves and can sustain a little higher temperatures.

Mike has some great articles, books and videos if you want more detail.

[Tim Jodice]

On 4/12/2021 at 10:54 PM, LANCECASPER said:

First thing I would check is engine baffle seals. Most of them are neglected and are worn out. They blow back under pressure and let air over the top and out the back of the engine rather that forcing the air down over the fins. The infinitely adjustable cowl flaps on your K model (and the M also) cn help keep things cool, and are useful even with good baffle seals.

I bought an Encore in 2014 and on the pre-buy this is what the baffle seals looked like.

No wonder after only 750 hours TT he had to replace the cylinders.

@GEE-BEE Guy Ginbey makes a set of die-cut baffle seals to fit your 252. It was the first thing I did after buying this airplane. I also did it on the airplane I have now, an M model. It makes a huge difference.

+1 for @GEE-BEE I bought a set for my plane and the fit and finish is awesome, no trimming required. I also saw a improvement. I didn't take any pictures before but this is how it looks after. notice no wrinkles.

[r0ckst4r]

On 4/16/2021 at 7:53 AM, FlyingDude said:

Hi,

Is there anything like "too low temperatures also lead to wear"? Is it e thing? 

Thanks

This has definitely been discussed, follow the link.  The tl;dr is keep it in the green arc and within the manufacturer recommendation.

 

[Will.iam]

19 hours ago, GEE-BEE said:

Change the seals and advise

you can’t make them from a 3” roll as you have compound curves.

GB

Gee bee i might be buying a top seal from you as mine is silicone and looks new but is a tad too long and buckles away from the top cowl in 2 places. When the top is put on.  Fortunately i can get a piece of duct tape over the buckled part tape it down since it’s right next to the oil filler door in the top cowl. I flew it yesterday and it helped alot.  I’m close to an oil change and will take pictures then when i take the cowl off for the oil change. 

[Will.iam]

Ok finally got to changing my oil and took a couple of pictures of the baffles with the cowl off. I circled in blue the area where the baffle buckles away from the cowl top when it is on. So far since it is right next the oil access door to check quantity i have just used a piece of speed tape to keep it held up flush with the cowl. I’ll bring it up at annual as I’m sure an AP can trim it to fit better. It does lower the temps but hard to quantify since OAT been changing

[carusoam]

Will.I.am’s

aerobatic plane after the show...

-a-

[A64Pilot]

You have what I believe many have, and that’s a good attempt in making a flat piece bend around compound curves by cutting it into pieces and putting it back together.

‘Unless I’m mistaken custom seals may be available that will fit a whole lot better

Edited May 7, 2021 by A64Pilot