Cht trouble

[Grant_Waite]

I have a 1977 M20J with the IO360-A3B6D. I have a whole jpi830 monitor with all the options. For whatever reason my #3 and #4 cht won’t stay below 380 unless I’m right on edge of lop, or very very rop. I experimented today and the only way to run 50°rop or 75° rop or even 25°lop, was with my cowl flaps open a bit. I’m running wot and 2500rpm based off the recommendations I’ve seen by others here. I’ve played around with lower rpm and it doesn’t change the issue. I get normal mag drops and egt rises on run up, my mag will be due for the 500hr in about 30more hours. I do have a power flow exhaust and a challenger air filter. The temperature at 7500 today was around 50 to 60f, so quite warm for that altitude, but I’ve flown at 10k where it’s 40f outside and the same issue. Here’s some pictures of today’s flight. It could be baffles, mag timing, something else I’m not thinking of or completely normal. I just don’t seem to remember having any issue at all before my annual, about keeping temps down. 

[MikeOH]

Not sure I'm seeing much of a problem.  Looks ROP based on fuel flow of 12 gph.  I'm normally around 9 gph at 65% power with similar CHTs.

[Grant_Waite]

Yeah, it was about 120° rop. I normally like to run it at 9.5gal or so but I can’t do it without both #3 and #4 chts creeping well past 380

[MikeOH]

2 minutes ago, Grant_Waite said:

Yeah, it was about 120° rop. I normally like to run it at 9.5gal or so but I can’t do it without both #3 and #4 chts creeping well past 380

What's 'well past'?  In hot weather my hottest two may push 390. While it's nice to have everything sub 380, I don't panic as long as everything stays under 400.

[Grant_Waite]

1 hour ago, MikeOH said:

What's 'well past'?  In hot weather my hottest two may push 390. While it's nice to have everything sub 380, I don't panic as long as everything stays under 400.

I don’t know what’s well past, because I never let it get hotter than 390° I’d imagine if I did nothing to stop it, it’d keep going well into the 400’s. For engine longevity I like to try and keep the hottest cylinder in the 360s. It just seems odd that it decides to creep well past 380° even if I’m lop. The topics of rop and lop are so opinionated, I’ve never settled on what’s myth and what’s fact about either. 

[EricJ]

That's not very bad, so I suspect checking the baffle gaskets, baffle condition, etc., will be useful.   Your oil temp seems a bit high, too, so I suspect you just have leaks in the baffles or baffle gaskets.   You can put a flashlight in the oil hatch and see how much light you can see from the front inlets to get an idea of how well the baffle gaskets are seating against the cowl.

You're getting decent speed out of it, so the engine is running fine.

[Grant_Waite]

15 minutes ago, EricJ said:

That's not very bad, so I suspect checking the baffle gaskets, baffle condition, etc., will be useful.   Your oil temp seems a bit high, too, so I suspect you just have leaks in the baffles or baffle gaskets.   You can put a flashlight in the oil hatch and see how much light you can see from the front inlets to get an idea of how well the baffle gaskets are seating against the cowl.

You're getting decent speed out of it, so the engine is running fine.

Yeah, she’s pretty darn fast when you put the fuel to her. The engine was overhauled in 2019, I bought it in December of last year. Not sure if they replaced the silicone baffles then or not. I also thought my oil temp was a bit high. I run it between 6-7 quarts depending on how long I’ll fly. I’m assuming a higher oil temp would correlate to more oil being used or is that a false assumption? 

[EricJ]

14 minutes ago, Grant_Waite said:

 I’m assuming a higher oil temp would correlate to more oil being used or is that a false assumption? 

Generally not.   Higher oil temp in this case may just be a symptom of inefficient air flow in the cowl, e.g., baffle or baffle gasket leaks.

[Ragsf15e]

What surprises me a little is that it still gets warm lean of peak. Mine is noticeably cooler lean of peak and I tend to stay pretty close to peak, like maybe 10degrees or so.  
 

Admittedly, that’s a pretty warm oat at 7500’ compared to what I see.  
Are the cowl flaps properly adjusted when closed - ie are they open the correct amount?

[Grant_Waite]

 

1 hour ago, Ragsf15e said:

What surprises me a little is that it still gets warm lean of peak. Mine is noticeably cooler lean of peak and I tend to stay pretty close to peak, like maybe 10degrees or so.  
 

Admittedly, that’s a pretty warm oat at 7500’ compared to what I see.  
Are the cowl flaps properly adjusted when closed - ie are they open the correct amount?

I’m not entirely sure. In the closed position my cowl flaps are pretty much flush with the lower cowl. So flush that I get streaks from the aluminum of the cowl flaps, rubbing the lower cowl. I did have my cowl flap linkage come loose after a touch in go all the way in KPDK. I didn’t realize it until I got cruise and there was no force required to move the cowl flaps to the closed position. Turns out it was a nut that came loose but I’m assuming that’s how you change the position of them. The nut was on the left side linkage, where the linkage and cable enter the cabin. Since my plane doesn’t have infinitely adjustable cowl flaps, they stay open in cruise in position with the push pull control. If I pull the control aft of that position, the air pushes it the rest of the way back thus opening the cowl flaps. Is this how it’s supposed to function or is something wrong with it? 
Both of these pictures are old but just as a reference. Bottom one is from last year. 

Edited November 14, 2024 by Grant_Waite

[ArtVandelay]

When you lean do all the cylinders peak at about the same fuel flow?

[Ragsf15e]

8 hours ago, Grant_Waite said:

 

I’m not entirely sure. In the closed position my cowl flaps are pretty much flush with the lower cowl. So flush that I get streaks from the aluminum of the cowl flaps, rubbing the lower cowl. I did have my cowl flap linkage come loose after a touch in go all the way in KPDK. I didn’t realize it until I got cruise and there was no force required to move the cowl flaps to the closed position. Turns out it was a nut that came loose but I’m assuming that’s how you change the position of them. The nut was on the left side linkage, where the linkage and cable enter the cabin. Since my plane doesn’t have infinitely adjustable cowl flaps, they stay open in cruise in position with the push pull control. If I pull the control aft of that position, the air pushes it the rest of the way back thus opening the cowl flaps. Is this how it’s supposed to function or is something wrong with it? 
Both of these pictures are old but just as a reference. Bottom one is from last year. 

I think it might be important to get tge cowl flaps working right and in accordance with the maintenance manual.  They are surprisingly effective at changing the airflow and cooling.  It doesn’t sound like they are, but each model has some specific way to adjust them and im not sure about your J.

[Fritz1]

sounds like baffles, make sure they press against the cowl, don't count on ram air pressure to close the baffles, might as well swap CHT probes and clean probe connectors just to be sire they are reading right

[Yetti]

I had the #3 CHT start showing hot.    So I crimped the spade connectors CHT and EGT with a pair of Kliens ie good crimpers.   Surprising little corrosion on small low voltage stuff will cause problems.   Switched the spark plugs between 3 and 1.     Seems to have cleared up the issues.

[Grant_Waite]

Is it true that the number 3 cht that’s piggybacked for the Jpi, reads low on my 830? Because it always is very similar in temps to #4 but I thought I heard somewhere that in reality the #3 is actually 30° higher than what the 830 will display. 

[Grant_Waite]

2 minutes ago, Yetti said:

I had the #3 CHT start showing hot.    So I crimped the spade connectors CHT and EGT with a pair of Kliens ie good crimpers.   Surprising little corrosion on small low voltage stuff will cause problems.   Switched the spark plugs between 3 and 1.     Seems to have cleared up the issues.

My factory cht bounces all over the place, sometimes not reading at all momentarily. You can see it was in bad shape by those pictures. Yesterday it worked just fine the whole flight. It looks like the jpi has its piggyback underneath the probe. I replaced the connector and recrimmped the wire. I still need to tighten the tiny nut more though because you can move it left or right with your fingers 

[Yetti]

17 minutes ago, Grant_Waite said:

Is it true that the number 3 cht that’s piggybacked for the Jpi, reads low on my 830? Because it always is very similar in temps to #4 but I thought I heard somewhere that in reality the #3 is actually 30° higher than what the 830 will display. 

#3 has the worst air flow.   That is why it will read hotter.   The piggy back one is not going to be the same as direct probes.  Too many environmental variable.   The Dynon CHT probes use a screw in adapter and then a twist lock on the thermocouple.  

The Ring terminal crimp on the stock probe is yucky.   Redo it with these from Home depot.  a new ring terminal and some heat shrink for support.    All that stuff has 100mph wind blowing past it.   https://www.homedepot.com/p/Klein-Tools-Crimping-and-Cutting-Tool-for-Connectors-1005SEN/100352095     Use crimp slot with the bump in it.   All those wires should not just be hanging and flapping in the wind.   and it should not be rubbing on the engine.   That fuel line should have fire sleeve on it.  Or replace with the brown hose.

[Yetti]

On the factory you can use a pair of needle nose to gently tighten the nut.  Since you are going to take it all off and redo the ring terminal, take a wire brush and make the brass contacts all shiny.

[Grant_Waite]

1 hour ago, Yetti said:

On the factory you can use a pair of needle nose to gently tighten the nut.  Since you are going to take it all off and redo the ring terminal, take a wire brush and make the brass contacts all shiny.

Those pictures are old, that was before I replaced the ring terminal. I turned the terminal around to the back side. I don’t believe there’s anything for those wires to really attach to. It’s a hard place to take complete pictures of. 

[Yetti]

3 minutes ago, Grant_Waite said:

Those pictures are old, that was before I replaced the ring terminal. I turned the terminal around to the back side. I don’t believe there’s anything for those wires to really attach to. It’s a hard place to take complete pictures of. 

You make wire bundles for support. and then have the bundles go to the middle of the engine (as close a possible to the middle) to transition to the firewall.  That way when there is the least amount of movement.   The about 3 small tywraps should do the job to put those  2 wires together.    also there is supposed to be a large Adel clamp around the orange heater hose that ties to the lug on the end of the footwell.

 

[Grant_Waite]

5 minutes ago, Yetti said:

You make wire bundles for support. and then have the bundles go to the middle of the engine (as close a possible to the middle) to transition to the firewall.  That way when there is the least amount of movement.   The about 3 small tywraps should do the job to put those  2 wires together.    also there is supposed to be a large Adel clamp around the orange heater hose that ties to the lug on the end of the footwell.

 

Yeah, key word supposed to. It’s just held to intake manifold with zip ties through a clamp. Like I said there’s a lot you can’t see but can assume from the pictures. I’m going to fly my ass all the way to Maryland again next year, so Byron and Jack can sort all the riggetry out on it, at annual. There’s a lot that could be done better and the right way. 

[Yetti]

53 minutes ago, Grant_Waite said:

Yeah, key word supposed to. It’s just held to intake manifold with zip ties through a clamp. Like I said there’s a lot you can’t see but can assume from the pictures. I’m going to fly my ass all the way to Maryland again next year, so Byron and Jack can sort all the riggetry out on it, at annual. There’s a lot that could be done better and the right way. 

Think maintainers do alot of putting it back they way they found it and not know how it was supposed to be.  But then what maintainer thought that zip ties through a clamp was the right way to go.  I hate doing Adel clamps, but found that using Hemostats help.    Hemostats also may safety wire a bit easier

Edited November 14, 2024 by Yetti

[Larry]

Consider adjusting the cowl flaps so they are open 1/2" when you close them.  You'll get better air flow and according to a Mooney test pilot a very small increase in speed (1-2 kts).

[Grant_Waite]

22 minutes ago, Larry said:

Consider adjusting the cowl flaps so they are open 1/2" when you close them.  You'll get better air flow and according to a Mooney test pilot a very small increase in speed (1-2 kts).

I think that’s what I’m going to do. According to the service manual you can adjust them by the rods, they connect to. I don’t think the silicone in the baffles is bad, but I’m going to do the flashlight technique to see how well they seal up. 

[Grant_Waite]

1 hour ago, Yetti said:

Think maintainers do alot of putting it back they way they found it and not know how it was supposed to be.  But then what maintainer thought that zip ties through a clamp was the right way to go.  I hate doing Adel clamps, but found that using Hemostats help.    Hemostats also may safety wire a bit easier

Yeah, being in Maryland for a week spoiled me because Byron and Jack know how everything should be on a Mooney. Good thing she’s a fast J!