CHT temps

[Jim F]

4 hours ago, Shadrach said:

Even if it were missing, that would not cause your CHT issue.

Hi Shadrach,

I have seen problems with CHT cooling and the only thing found on inspection was detached seal from the aluminum baffle.  Reattached and the CHT came down.  My take away was that the airflow is dynamic inside the cowl during flight and must have vibrated or folded over.  Back in the day I replaced cowl seals two times a week on average.   I have said before in other threads, I look at the baffling and cowl seal like a water radiator, no air lead are expectable.

[Shadrach]

1 hour ago, Jim F said:

Hi Shadrach,

I have seen problems with CHT cooling and the only thing found on inspection was detached seal from the aluminum baffle.  Reattached and the CHT came down.  My take away was that the airflow is dynamic inside the cowl during flight and must have vibrated or folded over.  Back in the day I replaced cowl seals two times a week on average.   I have said before in other threads, I look at the baffling and cowl seal like a water radiator, no air lead are expectable.

Fair enough. The F model has no grommet in that area as far as I know ( none shown in IPC). My governor line is fire sleeved so there’s not much of a gap anyway. Even so, prior to sleaving it, CHTs were well controlled( high200s to low 300s in cruise).

It certainly is important to ensure proper airflow through the cowl both in volume and direction. However I’ve seen many planes with a lot of attention focused on things that don’t really do anything…Lord, deliver us from copious amounts of RTV. 

I think something else is going on that is either causing the top side flow to leak past the engine compartment or the bottom side is not evacuating air from the lower cowl for some reason.

 

[Ragsf15e]

2 hours ago, Shadrach said:

Fair enough. The F model has no grommet in that area as far as I know ( none shown in IPC). My governor line is fire sleeved so there’s not much of a gap anyway. Even so, prior to sleaving it, CHTs were well controlled( high200s to low 300s in cruise).

It certainly is important to ensure proper airflow through the cowl both in volume and direction. However I’ve seen many planes with a lot of attention focused on things that don’t really do anything…Lord, deliver us from copious amounts of RTV. 

I think something else is going on that is either causing the top side flow to leak past the engine compartment or the bottom side is not evacuating air from the lower cowl for some reason.

 

Or the power setting is around 75% at 50 rop at 8500’ and 5c oat… then the temps are actually pretty good!  

[Shadrach]

23 minutes ago, Ragsf15e said:

Or the power setting is around 75% at 50 rop at 8500’ and 5c oat… then the temps are actually pretty good!  

You might be right. Its been such a long time since I’ve run 50ROP that I don’t have much of a frame of reference.

[Wingover]

2 hours ago, Ragsf15e said:

Or the power setting is around 75% at 50 rop at 8500’ and 5c oat… then the temps are actually pretty good!  

I was at 22” MP and 2400 RPM so closer to 60%

[Ragsf15e]

2 minutes ago, Wingover said:

I was at 22” MP and 2400 RPM so closer to 60%

Gothcha.  Any idea where your egts peaked?  Just seeing their values (which admittedly don’t mean much by themselves), it seems like you were pretty close to peak, but definitely on the rich side… any idea how rich?

[Wingover]

8 minutes ago, Ragsf15e said:

Gothcha.  Any idea where your egts peaked?  Just seeing their values (which admittedly don’t mean much by themselves), it seems like you were pretty close to peak, but definitely on the rich side… any idea how rich?

I can’t remember for sure but maybe 50f.  Was told not to run on the lean side since the engine is new. Give it time before flying LOP.

[Ragsf15e]

8 minutes ago, Wingover said:

I can’t remember for sure but maybe 50f.  Was told not to run on the lean side since the engine is new. Give it time before flying LOP.

Fair enough.  Yeah, you can tell from the ff that it’s likely not lop.  At 60% power, you can pretty much run it wherever you want and not hurt it, however, if you’re trying to make it hot, 50 rop is pretty close to where you might set the mixture.  I would recommend trying it richer, like 100 rop.  Id expect to see closer to ~10.3gph and noticeable cooling in the chts.  There are folks on here who did break in lop, so i think it’s unlikely you’d have problems running lop as well and that would definitely be cooler.  If you’re interested in just taking a look, set up similar conditions to your picture and then lean until the LAST cylinder egt peaks.  Go about 10 degrees leaner (cooler).  Let it settle. I bet your chts will be ~320.  Ff will be ~8.8 and you will lose about 3kts.

[Ragsf15e]

19 minutes ago, Wingover said:

I can’t remember for sure but maybe 50f.  Was told not to run on the lean side since the engine is new. Give it time before flying LOP.

Im about to go flying, so ill set mine up just like you did and show you the temps.  I’m betting they’re similar although I have an F with the old intake.

[Jim F]

5 hours ago, Shadrach said:

Fair enough. The F model has no grommet in that area as far as I know ( none shown in IPC). My governor line is fire sleeved so there’s not much of a gap anyway. Even so, prior to sleaving it, CHTs were well controlled( high200s to low 300s in cruise).

It certainly is important to ensure proper airflow through the cowl both in volume and direction. However I’ve seen many planes with a lot of attention focused on things that don’t really do anything…Lord, deliver us from copious amounts of RTV. 

I think something else is going on that is either causing the top side flow to leak past the engine compartment or the bottom side is not evacuating air from the lower cowl for some reason.

 

Agreed Ross, just my 2 cents

[Ragsf15e]

3 hours ago, Wingover said:

I can’t remember for sure but maybe 50f.  Was told not to run on the lean side since the engine is new. Give it time before flying LOP.

Well shoot, I guess I was wrong!  I flew your power setting (as you said, it was very close to 50rop) in almost exactly the same conditions and it was significantly cooler than your engine.  My cowl flaps were full closed.  
Are you still breaking it in? 
Now of course, I have an F and you have a J so the cowl is different, but I wouldn’t think that yours would run that much hotter?  Maybe looking closer at the baffling is a good idea.

Here’s the engine monitor from the top picture…

Just for grins, the second photo is Lop and you can see it’s cooler (#3 is almost the same as it is closest to peak).

 

Edited March 17, 2024 by Ragsf15e

[Wingover]

7 hours ago, Ragsf15e said:

Well shoot, I guess I was wrong!  I flew your power setting (as you said, it was very close to 50rop) in almost exactly the same conditions and it was significantly cooler than your engine.  My cowl flaps were full closed.  
Are you still breaking it in? 
Now of course, I have an F and you have a J so the cowl is different, but I wouldn’t think that yours would run that much hotter?  Maybe looking closer at the baffling is a good idea.

Here’s the engine monitor from the top picture…

Just for grins, the second photo is Lop and you can see it’s cooler (#3 is almost the same as it is closest to peak).

 

Ha! That’s very interesting. Thanks for taking the time to share.  I looked at the baffles seals and found a small section that was bent backwards just over the last (closest to the firewall) cylinder on the pilot side. There’s also a little “fold” (from extra material) in the opposite corner that’s about 1/2” hole.

The engine has about 30 hours.  No oil consumption anymore but I guess it might run hotter still with a bit of extra friction from tight tolerances.  I was told that I should see a reduction in CHT temperature getting closer to 50 hours.

[ArtVandelay]

I can’t remember for sure but maybe 50f.  Was told not to run on the lean side since the engine is new. Give it time before flying LOP.

I run LOP I’m below 75%, when I did initial breakin flight after overhaul (2 Hours of 75% or above) it was ROP. CHTs started out around 425° but were down to around 400° by end of the flight. After a couple of other flights 65%-75% LOP the CHTs continued to drop.
Air temperatures during these flights were about 80°.
I also had my fuel pump making more than book limit of 30 psi, by end of 10 hours it back to normal as well.
After that I had the prop dynamically balanced.

[Ragsf15e]

7 hours ago, Wingover said:

Ha! That’s very interesting. Thanks for taking the time to share.  I looked at the baffles seals and found a small section that was bent backwards just over the last (closest to the firewall) cylinder on the pilot side. There’s also a little “fold” (from extra material) in the opposite corner that’s about 1/2” hole.

The engine has about 30 hours.  No oil consumption anymore but I guess it might run hotter still with a bit of extra friction from tight tolerances.  I was told that I should see a reduction in CHT temperature getting closer to 50 hours.

Those baffling issues might help.  Use that light in the oil door technique to see any others.  Good luck!

[Ragsf15e]

5 hours ago, Ragsf15e said:

Those baffling issues might help.  Use that light in the oil door technique to see any others.  Good luck!

And checking which cht probe is different on the 830…

[ArtVandelay]

An easy sanity check is before you start the engine, check the CHT and EGT temperatures to see if they match the ambient temperature.

[Wingover]

2 minutes ago, ArtVandelay said:

An easy sanity check is before you start the engine, check the CHT and EGT temperatures to see if they match the ambient temperature.

Will do!

[Wingover]

On 3/16/2024 at 3:10 AM, Jim F said:

The red oval shows the missing rivets

@Jim F Would you know the part number for that grommet?  Looking the the parts catalog I don't see it.

[Jim F]

Hi Wingover,

I don't have the part number but you can measure the tube OD and the opening in the baffling.  Then search the web or a hardware store.  When you get the new grommet just cut and roll it in place.

Jim

[Wingover]

On 3/17/2024 at 8:51 PM, Wingover said:

Will do!

Went flying today.  CHTs and EGTs were at ambient temperature so I guess they work fine.

[Wingover]

On 3/17/2024 at 2:37 PM, Ragsf15e said:

Those baffling issues might help.  Use that light in the oil door technique to see any others.  Good luck!

So it seems that the baffling seals are now fine.  Went for an hour flight at 2000 ft.  After takeoff levelled off and set engine to 22” 2400 rpm with cowl flaps closed.  Leaned to 7.5 gph and temp was 10c over ISA so about 25c on the ground. Highest CHT on #1 stayed at 377/380 lowest was #4 at 330/340

I will check the probs next time.

Edited March 24, 2024 by Wingover

[Aerodon]

I think you are chasing your tail.  First, you have a new engine, go fly it hard for a while, only concern is not to let the temps go over 400.  Then check which cylinder might have a different probe location, just so you know.

Then go learn all about the Gami 'spread'.  Once you understand which cylinder peaks first, 2nd, 3rd, 4th and how the EGT's and CHT's follow one another (or not) you will start to understand why one cylinder is hotter than the rest.  Is more likely unbalanced fuel and air rather than cooling and baffles.

And then cylinders are just different, both in manufacture, location on the engine, baffling, airflow etc.

I don't think you have an unreasonable spread at all.

 

Aerodon

 

 

 

 

 

 

[mooneyflyfast]

This has come up several times over the years.  There is a small  aluminum angle in front of the number 1 cylinder. You can see it looking through the front cowl. It serves no purpose other than reducing air flow over the number one cylinder. My mechanic made a new one about 1/2 inch shorter from scrap aluminum angle.  It took him about  10 minutes.  My no. 1 went from the hottest to coolest.  Problem solved.

 

[Wingover]

I wanted to revive this thread as I went flying again and after landing I looked inside the cowl to find the rear seal folded back from the wind pressure.  I am wondering if the material is too thin or not long enough that it blows back.  What thickness do more of you use/have?

[ArtVandelay]

I wanted to revive this thread as I went flying again and after landing I looked inside the cowl to find the rear seal folded back from the wind pressure.  I am wondering if the material is too thin or not long enough that it blows back.  What thickness do more of you use/have?

I used 3/32”, which was much thicker than the original.