Too lean, too rich... nothing works

[Glen Davis]

So here’s the situation. I am at 8000 feet today at 75% power in my M20J. I have a 30 knot headwind so I’m running it hard for best speed.  I’m at 2600 rpm and 24 inches.    My cylinder head temperatures started creeping up close to the 400 mark. I tried running lean of peak, 8.7 GPH and the CHT’s stayed high. I tried running rich of peak at 13.5 GPH and my CHT’s still stayed high. The only way I could bring my cylinder head temperatures down would be to open the cowl flaps to their first notch. That brought the CHT’s down to 350, But I also lost about five or six knots. The outside temperature today was hot. On the ground it was 90+. Do others have this problem? My baffling looks good to me but I am not a mechanic. Any thoughts?

[A64Pilot]

By all means open the cowl flaps, that’s what they are for, cooling the engine. At power settings like that this time of year I can’t close mine all the way either.

5 kts sounds like a lot, but it’s better than cooking the motor.

LOP as it reduced the power should have cooled things some, if you didn’t lose power and of course speed, then you weren’t LOP

 

Climb or descend to find lower winds, or just live with it, at least your not in a Cub

Edited June 27, 2021 by A64Pilot

[A64Pilot]

You shouldn’t have been able to get 24” at 8000 ft?

[flyingchump]

Try lowering the rpm's?  Lots of internal friction creating heat.

[ArtVandelay]

Check the obvious, make sure your baffles are properly oriented.

 

There are not any that are folded backwards, they should be towards the engine.

 

If there’s a opening, the air takes the path of least resistance, and will not be forced down through the cylinders.

[Glen Davis]

1 hour ago, A64Pilot said:

You shouldn’t have been able to get 24” at 8000 ft?

Well, you’re right. I was between 23 and 24 with ram air open 

[carusoam]

2 hours ago, flyingchump said:

Try lowering the rpm's?  Lots of internal friction creating heat.

+ 10% more power being used…. Burning more fuel, while keeping the cooling the same… 

PP thoughts only, not a mechanical engineer…

Best regards,

-a-

 

See if we can define what Glenn is trying to achieve….

CHTs in flight at 8k’ are near 400°F… in a M20J…

Comparing what you see… to others….  High power settings equals high CHTs…

1) We can burn less fuel… pull back on the throttle… or prop, or both…  decreases heat generation…

2) We can add more coolant… go further ROP. (13gph is a lot of fuel being pushed through the engine…)

3) We can do both… go LOP… 

4) Use the cowl flaps… that is why they are there… increases cooling…

5) Most people cruising with a four cylinder Lycoming around here report FF nearer to  10gph…

6) Use caution while leaning…. Cruise At 13gph may be a bit above 65%bhp?

7) Keep in mind… I fly an M20R LOP using 13gph…  and spread the heat out over another pair of cylinders resulting in cruise speeds of about 165kts…

8) Keep in mind… flying in flaming dragon mode is an acceptable practice…  expect CHTs to be higher than more conservative modes of operation…   

9) For some people… Speed is everything…

10) How hot is 400°F?   When generally targeting 380°F for best cylinder wear…  is this one hour out of 2k… or all summer long?

11) Might want to share that data to support the conversation…

PP thoughts only, not a CFI…

Best regards,

-a-

 

[bradp]

1) baffles - shine a light through oil access door   If you see light though the front cowl openings, your cooling air is missing your cylinders.  Have your seals ever been changed? Mine were awful and it’s not a difficult job - results are impressive.  You can DIY with AP supervision with a roll of silicone - or Guy Ginby has some high quality kits.   

2) cowl flap rigging - ensure they are rigged about 1/4 - 1/2” open in trail in the “closed position” for summer flying.  Maybe Don Maxwell had an article about rigging on his website.  Yes on hot days you may need to run them in trail, but usually only ROP. Proper rigging can give you almost the cooling of in trail position without the drag. 

3) oil cooler clean? what are your oil temps doing?

4) you have an engine monitor, Correct?  Something seems not so LOP if your CHTs are still that high.   How far LOP?  8.7 gph at 8k doesn’t seem very LOP off the top of my head - maybe 10-15 LOP.  Get down to 50 LOP and see what happens.  

 

My bet is your baffles are torn up or flipped backwards. 

[mooneyflyfast]

On my J when temps get to ~400 I monitor the digital CHT of the hottest cylinder.  I then slowly  lean until the temp. starts down. This is a slow prcess so don’t rush it.  I’ve never not been able to get the temps. down to an acceptable value.  You will lose some speed but hopefully not as much as 1 notch of cowl flaps.  I have heard of rigging the cowl flaps to be slightly open in the closed position which should help.

Edited June 28, 2021 by mooneyflyfast

[Ryan ORL]

27 minutes ago, bradp said:

2) cowl flap rigging - ensure they are rigged about 1/4 - 1/2” open in trail in the “closed position” for summer flying.  Maybe Don Maxwell had an article about rigging on his website.  Yes on hot days you may need to run them in trail, but usually only ROP. Proper rigging can give you almost the cooling of in trail position without the drag. 

I recently did this to my J and it helped a lot.  No noticeable drag penalty, and it gave me probably 10 degrees cooler temps.  I live in FL, so in the summer, it's definitely plenty hot enough.

Doing this for warm weather flying is explicitly endorsed by the maintenance manual, so it's probably one of the first things I'd look at doing.  It's very easy and makes a big difference.

[PeteMc]

Baby it's col... er... HOT outside!  What part of the country are you in?  Here in the northeast it is hot right now.

As others have said, I'd probably have to have my cowl flaps open a bit today.  Also, as said, knock down the RPMs.  Though I hear you that you're fighting a headwind.  Also guessing that 8K was the best for the headwinds and going down or up, even with less power, would not have helped?

[Niko182]

Guys baffle kit is a good solution. Decreased my CHTs like 25 degrees right off the bat.

[PT20J]

The early J models had a flat left cowl flap. Later models had one with a curved opening that matches the right where the tail pipe is. Bob Kromer claims that adjusting the cowl flap for a small opening can actually create a slight speed increase. If you have the flat one, you might try adjusting the rod to open it half a inch or so and see what happens.

Skip

[Ragsf15e]

17 hours ago, Glen Davis said:

So here’s the situation. I am at 8000 feet today at 75% power in my M20J. I have a 30 knot headwind so I’m running it hard for best speed.  I’m at 2600 rpm and 24 inches.    My cylinder head temperatures started creeping up close to the 400 mark. I tried running lean of peak, 8.7 GPH and the CHT’s stayed high. I tried running rich of peak at 13.5 GPH and my CHT’s still stayed high. The only way I could bring my cylinder head temperatures down would be to open the cowl flaps to their first notch. That brought the CHT’s down to 350, But I also lost about five or six knots. The outside temperature today was hot. On the ground it was 90+. Do others have this problem? My baffling looks good to me but I am not a mechanic. Any thoughts?

Yesterday I flew from Tillamook OR to Spokane at about 3:30pm.  Not exactly the best thing to do as temps were ridiculous.  99f at TMK, 104f at SFF.  10,500’ was 14c.  It was wicked hot.  So I learned a lot about my airplane, just like you.  Normally I have no issues with cylinder or oil temps.

On takeoff, I expected a slow climb, but didn’t expect the oil temp climbing immediately above 200 even with 380s cylinder temps.  Oil temp maxed at 210 and aircraft climbing (slowly) at 130mph.  Stayed rich to keep cylinders cool, but eventually had to reduce rpm to help keep oil temp down.  As I climbed, I really had to fight to keep cylinder and oil temps down, air temps were isa+33ish.  Cylinders wanted to climb towards 400 without me taking action.  As the air got cooler, it also got thinner and didn’t cool as effectively.

I leveled at 11,500 initially but went down to 10,500’ soon after.  Cruise was just as you described.  I initially was LOP which typically yields 320ish chts.  Instead I saw 390.  Opening cowl flaps helped slightly.  I tried Rop and quickly gave up at 400cht.  Oil temp was about 200 now.  I went back to LOP and then went back to ~2450rpm and maybe 40LOP which is too far lop at 10,500’ but it cooled the engine.  I was only getting 133kts. Typically I see 140 LOP at 10,500.

All this is to say the temps aloft had a much bigger effect than I expected. I probably wouldn’t do that again as it was nearly constant work to keep temps in check during a very slow climb and cruise wasn’t much better.

Finally, I lived in south Texas with this airplane for a year and don’t remember it being this bad?  Maybe I only flew in the morning?

 I do have a SF mag which increases my cylinder temp slightly at higher altitude.

[Shadrach]

17 hours ago, Glen Davis said:

So here’s the situation. I am at 8000 feet today at 75% power in my M20J. I have a 30 knot headwind so I’m running it hard for best speed.  I’m at 2600 rpm and 24 inches.    My cylinder head temperatures started creeping up close to the 400 mark. I tried running lean of peak, 8.7 GPH and the CHT’s stayed high. I tried running rich of peak at 13.5 GPH and my CHT’s still stayed high. The only way I could bring my cylinder head temperatures down would be to open the cowl flaps to their first notch. That brought the CHT’s down to 350, But I also lost about five or six knots. The outside temperature today was hot. On the ground it was 90+. Do others have this problem? My baffling looks good to me but I am not a mechanic. Any thoughts?

1) 24inHg on a day that is 30 degrees above standard at 8000' seems a bit optimistic.

2) that is over 80% hp according to my POH at which 13.5gph is neither rich enough nor lean enough.

3) How long did you run at 8.7GPH? That's about 65% power and should have generated comfortable CHTs in short order.

3) You likely have an airflow problem, not a mixture problem.  

 

[Ragsf15e]

10 minutes ago, Shadrach said:

1) 24inHg on a day that is 30 degrees above standard at 8000' seems a bit optimistic.

2) that is over 80% hp according to my POH at which 13.5gph is neither rich enough nor lean enough.

3) How long did you run at 8.7GPH? That's about 65% power and should have generated comfortable CHTs in short order.

3) You likely have an airflow problem, not a mixture problem.  

 

I generally agree with you, except for  #3.  It was so hot yesterday, i was down around 8.3gph at 10,500’ to get it to cool down.  Normally I can run right at 9gph LOP and it’s real cool like you said, but we’re so far above standard temps, I think it’s not perfect.

[Shadrach]

13 hours ago, Ragsf15e said:

I generally agree with you, except for  #3.  It was so hot yesterday, i was down around 8.3gph at 10,500’ to get it to cool down.  Normally I can run right at 9gph LOP and it’s real cool like you said, but we’re so far above standard temps, I think it’s not perfect.

I know its been miserably hot in the PNW.  While your heat wave is a bit hotter than our normal mid summer weather, we operate regularly in the mid to high 90s here in Maryland with little trouble.  I have never had temp trouble in cruise at any altitude that cannot be resolved with more air or more fuel. I cannot say the same for climb. On the hottest days I used to have to really be mindful of climb performance to maintain healthy CHTs. I still do that but not to the same degree.  The last time I had my fuel servo rebuilt (11 years ago), I had my IA ask the overhauler (Aircraft Fuel Specialists Ltd.) to set the servo up as rich as possible within specs.  Ever since install I have enjoyed full power, full rich EGTs in the mid 1100s. I have never since felt short on fuel flow at any time.

Edited June 29, 2021 by Shadrach

[jaylw314]

 

2 hours ago, Ragsf15e said:

Yesterday I flew from Tillamook OR to Spokane at about 3:30pm.  Not exactly the best thing to do as temps were ridiculous.  99f at TMK, 104f at SFF.  10,500’ was 14c.  It was wicked hot.  So I learned a lot about my airplane, just like you.  Normally I have no issues with cylinder or oil temps.

On takeoff, I expected a slow climb, but didn’t expect the oil temp climbing immediately above 200 even with 380s cylinder temps.  Oil temp maxed at 210 and aircraft climbing (slowly) at 130mph.  Stayed rich to keep cylinders cool, but eventually had to reduce rpm to help keep oil temp down.  As I climbed, I really had to fight to keep cylinder and oil temps down, air temps were isa+33ish.  Cylinders wanted to climb towards 400 without me taking action.  As the air got cooler, it also got thinner and didn’t cool as effectively.

I leveled at 11,500 initially but went down to 10,500’ soon after.  Cruise was just as you described.  I initially was LOP which typically yields 320ish chts.  Instead I saw 390.  Opening cowl flaps helped slightly.  I tried Rop and quickly gave up at 400cht.  Oil temp was about 200 now.  I went back to LOP and then went back to ~2450rpm and maybe 40LOP which is too far lop at 10,500’ but it cooled the engine.  I was only getting 133kts. Typically I see 140 LOP at 10,500.

All this is to say the temps aloft had a much bigger effect than I expected. I probably wouldn’t do that again as it was nearly constant work to keep temps in check during a very slow climb and cruise wasn’t much better.

Finally, I lived in south Texas with this airplane for a year and don’t remember it being this bad?  Maybe I only flew in the morning?

 I do have a SF mag which increases my cylinder temp slightly at higher altitude.

You are a brave, brave man, my friend.  We spent the weekend in Astoria and I drove because of the weather forecast 

[N201MKTurbo]

21 minutes ago, Shadrach said:

We operate regularly in the mid to high 90s here in Maryland with little trouble. 

My engine would be so happy to run at such cool OATs!

Yesterday I flew to Yuma AZ, it was about 5 degrees cooler than it has been it was only 113.

I had to wear my winter gloves I keep on the hat rack for brushing the snow off when I'm in those conditions, to keep from burning my hands while hooking up the tiedown chains.

[Shadrach]

Just now, N201MKTurbo said:

My engine would be so happy to run at such cool OATs!

Yesterday I flew to Yuma AZ, it was about 5 degrees cooler than it has been it was only 113.

I had to wear my winter gloves I keep on the hat rack for brushing the snow off when I'm in those conditions, to keep from burning my hands while hooking up the tiedown chains.

Yes but it's a dry heat...

[Skates97]

15 minutes ago, N201MKTurbo said:

My engine would be so happy to run at such cool OATs!

Yesterday I flew to Yuma AZ, it was about 5 degrees cooler than it has been it was only 113.

I had to wear my winter gloves I keep on the hat rack for brushing the snow off when I'm in those conditions, to keep from burning my hands while hooking up the tiedown chains.

I feel you... We left Pagosa Springs, CO KPSO yesterday morning, it was a nice 55°F outside and landed in KIWA where it was approaching 100°F. We spent the day with my folks and took off at 18:00 for the trip back to SoCal when it was a balmy 111°F, we were the only GA plane moving at KIWA...

[Ragsf15e]

1 hour ago, Shadrach said:

I know its been miserably hot in the PNW.  While your heat wave is a bit hotter than our normal mid summer weather. We operate regularly in the mid to high 90s here in Maryland with little trouble.  I have never had temp trouble in cruise at any altitude that cannot be resolved with more air or more fuel. I cannot say the same for climb. On the hottest days I used to have to really be mindful of climb performance to maintain healthy CHTs. I still do that but not to the same degree.  The last time I had my fuel servo rebuilt (11 years ago), I had my IA to ask the overhauler (Aircraft Fuel Specialists Ltd.) to set the servo up as rich as possible within specs.  Ever since install I have enjoyed full power, full rich EGTs in the mid 1100s. I have never since felt short on fuel flow at any time.

I think it’s the +33c above isa at altitude that’s doing it.  I have enough fuel flow during climb to eventually keep temps down although it requires definitely using less than normal target egt.  Cruise just required less fuel running LOP.

Maybe you’re right, I could have cruised ROP, but didn’t want to cruise 200+ degrees rop, so maybe it was just a choice?

Edited June 28, 2021 by Ragsf15e

[Ragsf15e]

1 hour ago, jaylw314 said:

 

You are a brave, brave man, my friend.  We spent the weekend in Astoria and I drove because of the weather forecast 

Brave or stupid.  Had my family with me.  Actually everyone did fine.  Kids were so tired from playing at the beach they slept from takeoff to 11,500’ where it was cool.  Woke up, looked at a real volcano (st Helens) and asked to watch movies.  Even my wife did ok.  However, I think you’re right that I might not do that again…

Edited June 28, 2021 by Ragsf15e

[Shadrach]

31 minutes ago, Ragsf15e said:

I think it’s the +33c above isa at altitude that’s doing it.  I have enough fuel flow during climb to eventually keep temps down although it requires definitely using less than normal target egt.  Cruise just required less fuel running LOP.

Maybe you’re right, I could have cruised ROP, but didn’t want to cruise 200+ degrees rop, so maybe it was just a choice?

At the end of the day, I was not there.  At the DA's you were flying, LOP stops being an attractive option for me if maintaining Mooney speed is a goal.  The other issue (for me anyway) is that as DA increases,  the mixture spectrum of smooth operation narrows.  I can run 100 LOP 2000msl at 12,500 I start to feel the power variation from cyl to cyl around 25-30LOP

Edited June 28, 2021 by Shadrach

[Bartman]

Obviously it’s hot outside now and this stress will uncover any weakness in the airflow affecting the engine and oil cooling systems.  Before I installed new cylinder baffle kit from @GEE-BEE AEROPRODUCTS I would see 380-390 in summertime climb. Since then which was about 5 years ago I have never seen anything close to that. I also agree to adjust the cowl flaps open about 1/2 inch in the summer and flush in the winter. BTW we flushed my oil cooler at engine rebuild last year and it made a big difference in the oil temps in cruise, and since the elimination of engine heat is also thru the oil cooler this can be a significant factor.