High CHT, 470 degrees +.

[N201MKTurbo]

I was just looking at Lycoming's fuel flow formula. It comes out to a full power fuel flow of 16.5 GPH, you are a little shy of that. I wonder if your carb could stand some scrutiny? 

What are other C owners seeing for max fuel flow?

[ragedracer1977]

52 minutes ago, MIm20c said:

Is that the same manual where the cylinder redline is 500 ish...if so you’re fine...  one inch is not enough IMO and you’ll get dead air around cylinder 4. Again just an opinion from an armchair mechanic playing with the kiddos this morning. 

I believe all Lycoming cylinders "feature" a 500 degree redline. 

Also, I tried opening them up wider and saw no difference

[ragedracer1977]

Just now, N201MKTurbo said:

I was just looking at Lycoming's fuel flow formula. It comes out to a full power fuel flow of 16.5 GPH, you are a little shy of that. I wonder if your carb could stand some scrutiny? 

What are other C owners seeing for max fuel flow?

It looks like I'm getting very close to that. 

 

[MIm20c]

I think one of the problems is our cowl flaps do not have side skirt around them. That IMO would really help pull the air down and out. 
 

To be honest I’m having a similar problem (cyl 4 can increase to 415 during climb) which has ironically gotten worse after I sealed up the doghouse really well. I just reduce MP to 25 squared and it goes away. 

[Shadrach]

22 hours ago, HRM said:

We can agree to disagree. You're right in saying that these engines run hot, but they seem to run extra hot in Mooneys unless all the Mooney-specific parts (baffling, exhaust, etc.) are right.

Riddle me this, same airframe with two engines (O360 and IO360) of the same displacement, number of cylinders and ignition timing. One has some enhanced cooling features (IO360) a different intake system, slightly different cylinder head and higher compression ratio. Both engines will make 159hp at 2500rpm when full rich (88.5% power for the O360 and 79.6% power for the IO360). However, the the spec fuel flow for the IO360 is 12% (1.6gph) higher. 

Another curiosiy is that the POH’s show that the O360 can pull an extra inch of MP over the IO at the same temp and altitude.

This tells me two things. Firstly it appears the O360 is considerable under fueled compared to the IO360 and secondly the POHs are loose interpretations of the actual numbers.

this also tells me that almost any decrease in fuel flow to a cylinder will make for dramatic results in CHTs.

 

Edited April 9, 2020 by Shadrach

[ragedracer1977]

56 minutes ago, N201MKTurbo said:

I was just looking at Lycoming's fuel flow formula. It comes out to a full power fuel flow of 16.5 GPH, you are a little shy of that. I wonder if your carb could stand some scrutiny? 

What are other C owners seeing for max fuel flow?

One thing to add.  I haven't fully calibrated the fuel transducer.  It's possible that what the report is showing is slightly high or low

[ragedracer1977]

3 minutes ago, Shadrach said:

Riddle me this, same airframe with two engines (O360 and IO360) of the same displacement, number of cylinders and ignition timing. One has some enhanced cooling features (IO360) a different intake system, slightly different cylinder head and higher compression ratio. Both engines will make 159hp at 2500rpm when full rich (88.5% power for the O360 and 79.6% power for the IO360). However, the the spec fuel flow for the IO360 is 12% (1.6gph) higher. 

Another curiosiy is that the POH’s show that the O360 can pull an extra inch of MP over the IO at the same temp and altitude.

This tells me two things. Firstly it appears the O360 is considerable under fueled compared to the IO360 and secondly the POHs are loose interpretations of the actual numbers.

 

From everything I've read, I believe the O-360 is under fueled 

[Shadrach]

1 minute ago, ragedracer1977 said:

From everything I've read, I believe the O-360 is under fueled 

So we can further say that even the smallest decrease in spec fuel flow will affect dramatic and detrimental effect on engine cooling (see what I did there).  If you have indeed ruled out intake leaks, I would look at the carb.  My injected engine runs all cylinders well over 300rop on take off when full rich. 220 is not a lot of margin. I would say 250ROP is minimum and that would be just barely acceptable.

[takair]

9 minutes ago, Shadrach said:

So we can further say that even the smallest decrease in spec fuel flow will affect dramatic and detrimental effect on engine cooling (see what I did there).  If you have indeed ruled out intake leaks, I would look at the carb.  My injected engine runs all cylinders well over 300rop on take off when full rich. 220 is not a lot of margin. I would say 250ROP is minimum and that would be just barely acceptable.

Ross...I agree with what you say, but I am curious the best way to establish how much ROP one is at TO power.  I’ve been hesitant to test directly via mixture for fear of detonation.  I don’t have fast acting thermocouples, so it feels like an eternity for the temps to stabilize.  My CHTs are cool, but by extrapolation at higher altitude, I am not convinced I get quite 300ROP at sea level.  Are you extrapolating or do you have a recommended technique to get the number at TO power?

[Shadrach]

Just now, takair said:

Ross...I agree with what you say, but I am curious the best way to establish how much ROP one is at TO power.  I’ve been hesitant to test directly via mixture for fear of detonation.  I don’t have fast acting thermocouples, so it feels like an eternity for the temps to stabilize.  My CHTs are cool, but by extrapolation at higher altitude, I am not convinced I get quite 300ROP at sea level.  Are you extrapolating or do you have a recommended technique to get the number at TO power?

Well, I have never leaned to peak on take off but I have leaned to peak (from the lean side) at DAs in excess of sea level (both below and above) while running LOP down low. 3 of my CHTS peak in the mid 1400s with number three peaking in the low 1500s. My EGTs on take off are always in the mid to low 1100s. I enjoy a very cool running engine. Even in climb, 1 and 4 barely break  300°.  Save for the dead of summer, I have to lean in level flight to get all the cylinders above 300°

By the way the short term risks of detonation in a naturally aspirated four-cylinder Lycoming are small. Huge detonation margins.  I don’t think I could get my engine to detonate even if I tried. Perhaps with sustained with sustained, high powered flight leaned to 50ROP at low speed on the backside of the drag curve...but even then I’d likely have to wait for the CHTs to climb significantly before detonation might begin. 10 seconds at a high ICP mixture setting is not going to do it

[Shadrach]

Something else that is funny. According to Mooney at 2500’ the C model is not only faster than the F, it’ faster on less gas...

Edited April 9, 2020 by Shadrach

[HRM]

1 hour ago, Shadrach said:

Riddle me this, same airframe with two engines (O360 and IO360) of the same displacement, number of cylinders and ignition timing. One has some enhanced cooling features (IO360) a different intake system, slightly different cylinder head and higher compression ratio. Both engines will make 159hp at 2500rpm when full rich (88.5% power for the O360 and 79.6% power for the IO360). However, the the spec fuel flow for the IO360 is 12% (1.6gph) higher. 

No argument there. I really wasn't paying attention to the IO vs O aspect, clearly a factor.

That said, an E with all parameters correct (baffling, exhaust, fuel, spark, air, etc.) does not run hot. If it is running hot, something is wrong and most likely something with the Mooney specific parts.

Good luck with the C.

[Shadrach]

19 minutes ago, HRM said:

No argument there. I really wasn't paying attention to the IO vs O aspect, clearly a factor.

That said, an E with all parameters correct (baffling, exhaust, fuel, spark, air, etc.) does not run hot. If it is running hot, something is wrong and most likely something with the Mooney specific parts.

Good luck with the C.

Your first sentence sums up our disagreement. This is indeed an O vs IO issue.  Many C model owners are temp challenged where E model owners are not. Many cannot use all of the airframe’s climb performance because they have to drop the nose and or power to keep CHTs at an acceptable level. Most accept much higher CHTs than those of us flying behind IO360s. The E has all of the benefits I’ve mentioned in earlier posts given it is equipped with an angle valve IO360. This is why I said from the get go that this is a parallel valve O360 issue and has nothing to do with the airframe. Aviation journalists are fond of saying that “the tightly cowled Mooney’s tend to run hot”.  This is a load of horse manure. The under fueled O360s tend to run hot. Even in the best of tune under the best of conditions they tend to run much hotter than their more powerful injected brethren. This is why I believe this to be an O360 problem and not an airframe specific problem. Especially given that Brice has ruled out the airframe specific variables (doghouse issues).

Edited April 9, 2020 by Shadrach

[goterminal120]

I have a 68 model C, two mags , stock engine. My take off fuel burn is 18.5 gph regardless of da. Field elevation is 550’.

I had a hot #4 on take off, turned out to be exhaust leak. Took two look sees to realize it was leaking. Blowing right on the probe.

 For what it’s worth...and good luck.

    

[Skates97]

On 4/7/2020 at 8:43 PM, ragedracer1977 said:

Alot to reply to there lol.

Intake gaskets and rubber "slip joints" were  replaced not long ago.  Tubes were clean.

Carb has not been touched in over 1000 hours. I would have to pull the logbook to be certain.

How would I compare it to other o360 data?

 

If you're going to replace the carb you want to use the 10-4164-1, it is the richer of the carbs.

23 hours ago, M20Doc said:

A good friend of mine with a Comanche 180 has no issues with high CHT's on his Insight G2 after reworking the baffle sealing tapes.  It's the same basic engine as the C model Mooney.  I'm not sure about carburetor models but it does seem to be unique to the O-360, likely the carb jetting is too lean as both airframes have similar cowl designs.

Clarence

 

19 hours ago, Oscar Avalle said:

Indeed the carburetor is an issue. There are three different kind of carburetors. One of them is extra lean, that is the one that presents more issues. As I mentioned before you have to make sure that you have the right one.

Sent from my iPhone using Tapatalk Pro

 

It is a carb issue that the Mooney's have. I keep meaning to write up a post about my carb replacement journey, I'll try and start a thread on it tonight with all the data/info(work has been crazy cutting down on my MS during the day time...)

In a nut-shell...

There is the 10-3878, 10-3878M, and 10-4164. The "M" is just a modified 3878 which makes it the same FF as the 4164. I went back and forth on emails with Marvel-Shcebler and got some good information out of them. They had the specs from the bench test on my the 3878 that went in my plane in October which they tested at 16.7 GPH but I only saw 14.5-15 GPH resulting in much higher CHT's than I previously had. I have the JPI data from before the carb replacement, which apparently was a "M" despite nothing in the log books, the data with the 3878 that was put in last October, and the data from the 4164 that was put in last month. Some interesting numbers and how the FF on the different carbs acts as well as effect on EGT and CHT. More to come in a different thread, don't want to totally sidetrack this thread as I'm not sure that is Brice's problem?

[ragedracer1977]

24 minutes ago, Skates97 said:

If you're going to replace the carb you want to use the 10-4164-1, it is the richer of the carbs.

 

It is a carb issue that the Mooney's have. I keep meaning to write up a post about my carb replacement journey, I'll try and start a thread on it tonight with all the data/info(work has been crazy cutting down on my MS during the day time...)

In a nut-shell...

There is the 10-3878, 10-3878M, and 10-4164. The "M" is just a modified 3878 which makes it the same FF as the 4164. I went back and forth on emails with Marvel-Shcebler and got some good information out of them. They had the specs from the bench test on my the 3878 that went in my plane in October which they tested at 16.7 GPH but I only saw 14.5-15 GPH resulting in much higher CHT's than I previously had. I have the JPI data from before the carb replacement, which apparently was a "M" despite nothing in the log books, the data with the 3878 that was put in last October, and the data from the 4164 that was put in last month. Some interesting numbers and how the FF on the different carbs acts as well as effect on EGT and CHT. More to come in a different thread, don't want to totally sidetrack this thread as I'm not sure that is Brice's problem?

Let me know when you post it, id be curious to read it

[Skates97]

1 minute ago, ragedracer1977 said:

Let me know when you post it, id be curious to read it

Will do, I've just been trying to find the time to put it all together. And will just post a thread here than on my blog.

My wife doesn't read MS but reads every post on the blog. All she knows is that the AP/IA was doing some "stuff" to the carb while he was replacing the exhaust and then doing some other "stuff" to the carb later because the fuel flow was off. She's not aware of the purchase of two overhauled carbs in about a six month period of time...

[Shadrach]

32 minutes ago, Skates97 said:

If you're going to replace the carb you want to use the 10-4164-1, it is the richer of the carbs.

 

It is a carb issue that the Mooney's have. I keep meaning to write up a post about my carb replacement journey, I'll try and start a thread on it tonight with all the data/info(work has been crazy cutting down on my MS during the day time...)

In a nut-shell...

There is the 10-3878, 10-3878M, and 10-4164. The "M" is just a modified 3878 which makes it the same FF as the 4164. I went back and forth on emails with Marvel-Shcebler and got some good information out of them. They had the specs from the bench test on my the 3878 that went in my plane in October which they tested at 16.7 GPH but I only saw 14.5-15 GPH resulting in much higher CHT's than I previously had. I have the JPI data from before the carb replacement, which apparently was a "M" despite nothing in the log books, the data with the 3878 that was put in last October, and the data from the 4164 that was put in last month. Some interesting numbers and how the FF on the different carbs acts as well as effect on EGT and CHT. More to come in a different thread, don't want to totally sidetrack this thread as I'm not sure that is Brice's problem?

To be clear, I think Brice has a problem that is stacking on top of a system that has only marginal fuel flow (as you describe) when operating at its best.

[Shadrach]

19 hours ago, goterminal120 said:

I have a 68 model C, two mags , stock engine. My take off fuel burn is 18.5 gph regardless of da. Field elevation is 550’.

I had a hot #4 on take off, turned out to be exhaust leak. Took two look sees to realize it was leaking. Blowing right on the probe.

 For what it’s worth...and good luck.

    

You’re fortunate. That’s right at the book number for an IO360 on a standard day at sea level. Who ever set up your carb did you a favor. If every O360 had that kind of flow, most of the CHT trouble shooting threads would go away. A lot of O360 operators report 2-3gph less than that on take off at or around SL DA. How are your CHTs in climb?

Edited April 10, 2020 by Shadrach

[Shadrach]

4 hours ago, N201MKTurbo said:

I was just looking at Lycoming's fuel flow formula. It comes out to a full power fuel flow of 16.5 GPH, you are a little shy of that. I wonder if your carb could stand some scrutiny? 

What are other C owners seeing for max fuel flow?

Apparently they are not using their formula as a recommendation. That’s 1.7gph less than book for an angle valve making the same horsepower.

 

  

Edited April 9, 2020 by Shadrach

[0TreeLemur]

4 hours ago, N201MKTurbo said:

I was just looking at Lycoming's fuel flow formula. It comes out to a full power fuel flow of 16.5 GPH, you are a little shy of that. I wonder if your carb could stand some scrutiny? 

What are other C owners seeing for max fuel flow?

I get 16.5 on climb at full power for the flight I posted EDM data for earlier in this thread.

[Guest]

8 hours ago, ragedracer1977 said:

Was there meant to be pictures?

Oops!  Here you go

[ragedracer1977]

5 hours ago, M20Doc said:

Oops!  Here you go

Yeah, thats pretty much how mine looks.  I did some fuel flow calibration, and the FF transducer is now dead on.  Looking at the data, the fuel pressure started to drop right at 23.9 gallons used (24 gallon tanks).

On takeoff at max power, fuel flow barely went over 15 gph, and then only for about 15 seconds until falling into the mid 14.5 gph range.  I think I'm starting to lean towards needing carb work done.  At best, the carb has 1000 hours since overhaul, but it might be closer to 2000.  I forgot to look in the logs today.  I'll have to check that tomorrow.  

[carusoam]

Calibrating the EGT gauge is interesting....

Doing it during T/O is not recommended... too many other things going on... not to mention the high ICPs...

The Max EGT at peak power is pretty close to the max EGT at other altitudes... more of a chemistry / flame temperature issue... and how far the TC is from the flame...

 

The O’s EGT gauge isn’t much different than the M20C’s, except the O’s instrument is calibrated with numbers...

The 200-300°F ROP range is a permanent blue box...

 

So try it at an altitude that is red box safe... >8k’... and see if you can get 300° ROP... mark (grease pencil) the EGT gauge where peak occurs, and where 200 and 300 occur... now you have a calibrated EGT gauge using your JPI to do the calibrating...

There are a few things that will move the peak around ... but the blue box is a giant / safe approximation of excess fuel used for cooling...

It is extra hard to get too much fuel to the engine... when you can see it on the FF instrument...

We have all experimented with it at high DAs... using the target EGT method...   too cold... is too much fuel... and leads to lower power output than possible...

 

Rough estimates of what could be possible for FF based on other NA Mooney engines... to maintain better CHTs...

310hp 30gph...

200hp  20gph

180hp 18gph

It would be great to swap on a different fuel jetted carb for a simple experiment....

 

Of course this doesn’t account for why one cylinder is hotter than the rest...

 

That is a fuel distribution challenge...

Experiments to change this can include... adjusting the MP enough to close the secondary jet... see if distribution improves or gets even worse...

Closing the carb plate even more... this is known to improve air / fuel mixing to improve any attempts at going LOP...

If you get to fly it again... take it to altitude slowly...  seeing if the reduced VSI, increase ASI helps with the cooling...

Once at altitude... the mixture full in should provide a plethora of excess fuel for cooling... demonstrate how cool the EGT is... does it even exceed 300°F?

Altitude typical reduces the overall fuel burned, generating less heat... the cooling fins don’t change, neither does the air speed... the air density changes a bit...

 

Overall you are looking  to find a way to use excess fuel to improve the CHTs overall... by reducing the EGTs... and minimize any changes is air cooling... even though the OAT and density are decreasing...

Doing this you can prove if excess FF can help cool the cylinders...

Adjusting the throttle plate can prove changing the fuel distribution can help change the hottest cylinder...

 

PP thoughts only, all stuff I have learned on MS... 

Let me know if I can explain anything better...

Best regards,

-a-

[Guest]

7 hours ago, ragedracer1977 said:

Yeah, thats pretty much how mine looks.  I did some fuel flow calibration, and the FF transducer is now dead on.  Looking at the data, the fuel pressure started to drop right at 23.9 gallons used (24 gallon tanks).

On takeoff at max power, fuel flow barely went over 15 gph, and then only for about 15 seconds until falling into the mid 14.5 gph range.  I think I'm starting to lean towards needing carb work done.  At best, the carb has 1000 hours since overhaul, but it might be closer to 2000.  I forgot to look in the logs today.  I'll have to check that tomorrow.  

Here is the MSA Carburetor application guide, this plus the Mooney type certificate should help.

https://msacarbs.com/technical-data/engine-eligibility/

Clarence