Carbureted o-360 engine CHT/EGT temps on climb out?

[Wesley brown]

Yikes! 400 on climbout? If any of my cylinders hit that I would be inspecting the doghouse for holes.

Your engine can fly all day long at 2700 RPM. I only back the prop off just enough to verify it is working correctly, like maybe to 2650 during the climb to altitude. And never touch the throttle. Leave it balls to the wall. There is no reason at all to back off the throttle during the climb. I think there have been tons of documents written to that effect over the history of Mooney.

If your EGTs are at 1400 during the climbout, how high do they go at peak? Because while CHTs can be compared between all of us, we cannot really compare EGTs across different airplanes, because the sensors are installed in slightly different places. EGT is really only referenced with respect to whatever it peaks at, while CHT is an absolute temperature. If you are flying with high power levels and closer than 100 degrees richer than peak, you're in the "red box", mixture-wise, and might want to take a look at that. My EGTs are often up in the mid 1300's on takeoff, and that is of huge concern to me right now.

Dave Morris

N1960.com

I found out the other day when I turn my fuel pump on or any lights it raises all my Gauge's sperticaly . So climb out temps aren't true with the pump on. The dog house is tight. I have to track the grounding issues before I start getting worried. It sucks to have the gauges and not be accurate. I wanted to make sure so I scoped my pistons and everything is fine no indecation of burning them. Now when I turn my fuel pump off they all level off to around 350-360

[Jim Peace]

The pilot who has been flying my airplane has said that he has been experiencing High CHT and it is not normal for my plane.  He has hundreds of hours in this tail number.

 

This has happened since the annual where I had the left mag (slick) 500 hour inspection and also changed out all plugs to the tempest finewire UREM38S.  The plugs are the correct ones according to the Lycoming document.

 

I also have the LASAR cowl mod which when it was done last summer dropped the temps by about 40 degrees or more......so high CHT should not be noticed at all.

 

Ideas?

 

I have the document from lycoming on what could be the reasons but all was checked.

[xrs135]

What kind of CHTs are you seeing?

[Jim Peace]

What kind of CHTs are you seeing?

He said he was seeing just under redline .....but at cruise all is well....normally this plane is cool all the way up......

 

I wonder if it pays to remove the left mag and have it sent out to the shop so they can inspect their inspection......

[Wesley brown]

Mine does the same thing. It has been tracked down to electrical fault somewhere . When I turn my lights and other things in the gauge will climb up all by itself to 400 deg. I don't trust my gauges and plan on just changing them out to a newer monitor.

[ArtVandelay]

For those with high CHTs on climb, what are they at cruise? decent? Cowl flaps open, closed? Is your fuel flow at cruise match POH performance tables? Climb FF? It can't hurt to go out and get some more data points, helps to have an engine monitor that you can download data afterwards.

[BigTex]

David,

 

You have the same year C model that I have and I actually went in and increased the cowl flap opening by about an inch.  It really seemed to make a difference.  For what ever reason, the factory calls out the flap opening to be 1.1" which might be some of the issue.

[Andy95W]

Dave-

The doghouse itself is usually decent unless there is a huge sheetmetal crack (unlikely). Look hard at the lower front portion of the baffling, especially around the starter and alternator/generator. Also look at the rubber baffling where it mates to the front of the cowling around the wholeguppy mouth.

My cowl flaps also open much further than the maintenance manual says, and I'm not changing them. Easy to do, move the pusrod attaching bolts to the outer holes and adjust the rod end so the cowl flaps close all the way.

[Wesley brown]

I found the problem today! After sitting on the ground and playing with the plane I was switching the landing light on and all the sudden I see my CHT gauge jump to 400 degrees. Keep in mind I'm not running the engine! I called the gauge manufacture and they told me it only takes Mila volts to change the accuracy of the CHT gauge. They are the most sensitive. I have the plug probes that go around the spark plugs. So today I wen to the hanger to research the grounds sat the gauge only needs a ground to the engine block. I noticed my engine didn't have a ground going from the battery to the engine. This also caused my starter to really lag at times and wouldn't even turn the engine over . I thought my battery was going bad. With my plane being a wood wing I wanted to ensure that I had adequate grounds everywhere so I ran one to the engine from the battery and others to the airframe and firewall and other grounding stations. This helped tremendously . My number three cylinder has always been the hottest but I suspect a bad probe as it sometimes climbs dramatically on its own in level flight. Once it settles I see 380 on climb out now instead of 430 once leveled off I am seeing 340-350 all across. There is no hot temps on my plane just bad grounds on the new firewall forward that was just installed. I think I have one bad probe on my CHT and also two on my egt. Now I have better readings and my starter doesn't struggle at all. I also cleaned each ground attachment point they were grimy and not contacting sufficiently.

My cowl flaps open about 2.250".

I wish I had the money for a JPI !!!!

[Jim Peace]

Here is my CHT after taking off in over 90 degree temps and climbing to 6500 feet.  they were about the same in the climb.  Is bouncing around normal?

 

 

[Wesley brown]

For some reason I couldn't download the video. My gauges bounce when switching cylinders. It really nerve racking.

[xrs135]

Here is my CHT after taking off in over 90 degree temps and climbing to 6500 feet. they were about the same in the climb. Is bouncing around normal?

I honestly wouldn't worry about it. C's run hot... they always have, and and they always will... and plenty of them make it to TBO. They aren't exceeding Lycoming's "true" redline of 500F. I see probably 405-435 on mine during climb out no matter what I do. Cylinder 4 being my hottest cylinder right at 435... and all the others somewhere in the previously mentioned range. My cowl flaps are adjustable and rigged to open more than than the factory calls for, I have about 120hrs on a major overhauled engine - everything is new firewall forward... oil consumption 1qt/14hrs, FF is adjusted properly, doghouse is immaculate, I have the ARI cowl mod, and I climb at 120-130. I've stopped worrying about it. When I level off in cruise, and close the cowl flaps, #4 sits just below 400, and all the other are between 360-385.

My stock CHT gauge looks exactly like yours does in the video during climb. I have the EDM700 in my plane to verify all the temps... but honestly it's more frustrating having a JPI on a carbureted engine with the uneven fuel distribution than it's worth.

Back in the 60's/70's people didn't have all this fancy equipment to monitor temps, and they just had that crappy stock gauge (which if you go by that, the CHT's are within limits, even though they are "high" by modern-day standards.) They flew their planes, leaned by pulling the mixture out until roughness, then kicked it in a little bit... no "lean assist" or anything like that. These planes have been operated like this for their entire flying life, and they are still going.

Bottom line is that the C just isn't that efficient when it comes to engine cooling. Would I like it to run cooler? Sure. But at the same time, I try not to worry about it too much, and just fly my plane.

Oh, and reference one of the previous posts... My landing light seems to have no effect on CHT's indications on the stock gauge.

[Wesley brown]

XRS

I actually have seen the same numbers as you. Once I did the oil line reroute and flushed the oil cooler and found the ground issue it helped a lot but occasionally I'll see number two go from 360 to 390- back to 360 and on the flight home it stays at 400 in level flight. I know we have unequal distribution but I'm happy if I see 430 on climb and anything below 400 on level flight. I had a grumman that did the exact same thing Numbers wise. I'm flying it and have done everything to compensate fir correction.

[Wesley brown]

I have good news! I changed my champion 40 plugs to Tempest Urem37by plugs . I also installed new harness mags. What a difference in CHT temps!!! My engine dropped 30-40 degrees on climb out. Instead of 400-430 on cyl #2 I am now seeing 360-380. On cruise all of my cylinders are about 330 and number two is 350. This helped me lower my CHT tremendously!!!

I no longer feel a slight stubble or miss anymore either. It was barely noticeable.

I also cleared up my radio noise the harness wires were sending out a transmission and now my radios are crystal clear on reception.

[xrs135]

I have Champion 40's in my C. Maybe I should throw in some Tempest 37BY's and see if it makes a difference! I also have a barely noticeable stubble/miss as well I'd love to get rid of. The 37's are supposedly the "coolest" running plugs, right?

[Wesley brown]

I would do the change it was a great mod for me with minimal cost . I also did the change on my grumman traveler and I noticed cooler temp but I thought it was because we had just did a top overhaul? I'll never know? But the mooney the only change was mag harness and the BY plugs temps are way down nothing else changed!

[xrs135]

Cool. I'm going to go ahead and try it... I will report back!

[Wesley brown]

Good deal let us know!

[o-360]

I know this is an old post...but if you have the 10-3878 P/N carb there is nothing you can do to prevent these high CHTs on #3 and #4. 

Verify that if you have the 10-3878 that it has an "M" stamped on it...meaning it had the re-jet field mod. Marvel Schweber put out a service bulletin for high CHTs back in 1962. The main jet is too small for this engine.

Or...you can install the newer 10-4164-1 carb that has the mod already. 

My CHTs went from 440+ on climb out to <390...and during level off they dropped the same temp as the front ones...330.

All from swapping the carb to the 10-4164.

Jim   

[carusoam]

Great details on the carb jet for the O360, Jim!

Thanks for adding the detail…

Best regards,

-a-