M20C runs hot

[MQQNEY]

I recently purchased my first Mooney, an M20C Mark 21 1964, and am quite delighted with it. My one concern at this time is that operating temperatures are a little higher than what I would be comfortable with. I have heard tell before that this model has a tendency to do so, but i wouldn't have thought quite as warm as she does. It's the very top end of the green arc in climb and cruise, sometimes briefly beyond the green in climb, ( cylinder temp.), but gets nearer to the centre of the green when letting down on descent. Has anybody else had a similar experience, and. If so, any suggestions?

[gsxrpilot]

The M20C's do tend to run a bit warmer than later models. I used to fly around with my cowl flaps open all the time to help keep the temps down.

I eventually solved it with a combination of dog house and baffling work to seal up gaps and holes. But also by managing the throttle better. Once established in the climb, I would pull the throttle back as much as possible but WITHOUT reducing any manifold pressure.  In other words, don't move it very much. That gave me better mixture control, even fuel flow across all cylinders and cooler temps.

All that said, think about adding a proper engine monitor so you can see CHT's across all cylinders. The Insight G2 is my favorite considering value for money.

 

[tigers2007]

From what I have gleaned here, a lot of it has to do with the workmanship of the "doghouse" that surrounds the engine. I took these photos about a week ago. I recommend getting a nice graphic engine analyzer - if you go with Insight, get at least the G2 as it has logging amongst many other features. I too am a newer owner of a '64 D model (converted to retractable gear).

 

 

Sent from my iPhone using Tapatalk

 

[Seanhoya]

Don't forget leaning.  Rember, fuel cools the cylinders, so if you are aggressively leaving, you will run hotter. While I always aggressively leaned on the ground, on the air if I was running hot, I didn't.

Minimize your time idling and running up on the ground - this always caused the engine to run hotter.  

Put the cowl on the horizon for a good cruise climb.  This will force more air into the engine. Accept whatever airspeed this gives you.

Consider replacing the oil cooler and modifying your intake...The guppy hole of old Moonies just isn't good for cooling.

I don't know that you can totally "solve"this issue...I struggled with it for 8 years with a G model which didn't have cowl flaps.

 

[Raptor05121]

2 hours ago, Seanhoya said:

Don't forget leaning.  Rember, fuel cools the cylinders, so if you are aggressively leaving, you will run hotter.

 

Up to a point, and further leaning would cool cylinders dramatically.

[gsxrpilot]

1 hour ago, Raptor05121 said:

Up to a point, and further leaning would cool cylinders dramatically.

Where does that chart come from? It's not exactly accurate. You'd be better to use the similar, but more correct charts from APS.

https://www.advancedpilot.com/redbox.html

[Drumstick]

7 hours ago, Seanhoya said:

 

Consider replacing the oil cooler and modifying your intake...The guppy hole of old Moonies just isn't good for cooling.

 

 

Replace oil cooler with what?  What mods to the intake are you suggesting?  Just curious as I'm trying to improve my cooling as well.

[Hector]

Make sure your dog house is in good shape. Look for holes or any potential leaks. You want to make sure you are forcing as much air as possible through the cylinders for proper cooling. Any leaks detract from that. Look specially for leaks around your starter and generator/alternator

 

I climb at Vy to 1000 feet AGL and then immediately transition to cruise climb of 120 mph. In the middle of the summer you might need to go a little faster. This keeps my temps under 400 in the climb but still over 380 on some cylinders.

 

Mixture full rich to 3500 then target EGT. Look this up if you don't know what it is.

 

Some folks are proponents of full throttle climbs. I do it as much as possible, but in my C climbing at 26 square reduced cyl temps by 20 degrees in my JPI. interestingly enough it's also the climb setting recommended in my POH. Imagine that!

 

Do get an engine monitor. Money well spent and you will no be guessing how hot you are running

 

 

Cowl flaps always partially opened at a minimum. Or fully opened if you need them. The intake flow in early Mooneys is terrible and you need the back pressure of opened cowl flaps to improve the flow.

 

During cruise my temps all settle down in the 360 range or below. As much as I like to climb under 380 it's just not possible in my C

 

 

 

Sent from my iPhone using Tapatalk

 

[Hank]

2 hours ago, Drumstick said:

Replace oil cooler with what?  What mods to the intake are you suggesting?  Just curious as I'm trying to improve my cooling as well.

It's not the best picture of the front, but this is the guppy mouth closure. Zoom in for a better look.

I climb WOT, Vx to clear obstacles then Vy to Vy+10. When cruising above~7500 or so, i pull the throttle back just until the MP needle starts to move, set 2500 and lean. It's easy and works well. 

Edited March 12, 2017 by Hank

[Drumstick]

4 hours ago, Hank said:

It's not the best picture of the front, but this is the guppy mouth closure. Zoom in for a better look.

I climb WOT, Vx to clear obstacles then Vy to Vy+10. When cruising above~7500 or so, i pull the throttle back just until the MP needle starts to move, set 2500 and lean. It's easy and works well. 

Thanks Hank.  I figured it was the LASAR cowl closure mod but figured there might have been something else that was magical.  I have not heard of an oil cooler mod for the M20C.

[Raptor05121]

11 hours ago, gsxrpilot said:

Where does that chart come from?

 

 

It came from Lycoming themselves, the maker of said O-360

[Andy95W]

15 hours ago, gsxrpilot said:

Where does that chart come from? It's not exactly accurate. You'd be better to use the similar, but more correct charts from APS.

https://www.advancedpilot.com/redbox.html

The APS charts have the right side leaner as opposed to the Lycoming chart the has lean on the left side of the graph.  I prefer the APS chart, same as you.

[Jim Peace]

I have a 64 C as well....

my CHT is about 40 to 50 degrees cooler since I put the LASAR cowl mod on...also picked up a few extra knots.....

Also like many said,, climb with a faster speed.........

[carusoam]

Off topic swerve....

We have a few MooneySpace members in Australia...

If you want to reach out to other like planed individuals.

Best regards,

-a-

Edited March 13, 2017 by carusoam