Has anyone redirected their oil cooler airflow into the bottom cowl on a C model to improve engine cooling?

[DXB]

On 4/8/2022 at 9:57 AM, Chessieretriever said:

Maybe your engine is producing a beneficial incremental amount of power due to your power flow exhaust and therefore could benefit from the carburetor main jet change that Mooney proposed (larger main jet with different atomizing hole patterns on the jet). I know of a person with a C that uses this mod and requires 19.2 GPH on take off at sea level (also has to climb at 120MPH) and is able to keep temps on the 2/4 bank below 400F. Obviously he is cooling the cylinders with fuel. If all of this does not help perhaps you can take 1 or 2 degrees of timing out (retard it) to reduce the thermodynamic load on the cylinders and hence reduce your temperatures; this may be great on take off but will produce a slightly lower performance at altitude in cruise power settings. Last but not least maybe a little adjustment on the cowl flaps (trailing more open in the fully closed position to allow for a steeper angle when in the open position) associated with that side of the engine can help (mentioned already); there is a little room on the heim joint threads that could be utilized and still meet the specs.

Sadly already have the richer carb for the certified engine (there's a leaner carb, the leaner carb modified to match the richer version, and the richer version - the one i have) - can't get more than 18gph on it - the main jet can be reamed larger on the richer version, though not technically legal in the certified world.  

Sadly already retarded both sides to 23 (also not technically legal for the engine) - no much difference. If I retard it more, there may be a power dropoff...

The cowl flap modifications may be in my future - I have the fixed version on the '68 permanently set to 1.1" opening - no heim joints there...

[TPC]

@DXB

 

C driver to C driver,

My #3 & #4 cylinders run warmer in climb, then switches to #2 & #4 in cruise. I haven't had trouble managing the CHTs, even with surface temps +100. My typical initial climbs are 110-120 mph IAS - WOT - 2600rpm - 18-20 gph

I'll provide some further data for benchmarking. Hope it helps.

Mods:

• Lasar partial cowl closure
• Power Flow exhaust
• Surefly SIM <--saves 1 gph with +20 CHT@8500
• 10-4164-1 Carb
• Challenger air filter

JPI Data:

• 8500 ft - WOT(just off MP movement) - 2500 rpm - 8.5 gph - 147 kts TAS

[carusoam]

Nice data collection TPC!

The only thing better would include the link to the Savvy site…

This way people can read all the various data points if they wanted to…. 

Nice work!

Best regards,

-a-

[TPC]

@carusoam Great suggestion!

M20C JPI Data: 

• 8500 ft - WOT(just off MP movement) - 2500 rpm

https://apps.savvyaviation.com/my-flights/22748/8e869d44-a2bf-4967-9a0c-2d8e3c38362e

[carusoam]

TPC,

Have a look…

The EGT data often gives a hint to what may be happening with CHTs…

In this case…

The cooler CHTs are related to the cylinders with warmer EGTs…

I grabbed a pic from the most recent flight…

To add to the discussion…

With the carburetor… fuel distribution can be pretty widely spread… a Gami test will give a hint of how widely spread your fuel distribution is… Gami spreads near 0.0 are better than spreads >1.0….

-a-

 

 

[DXB]

On 4/21/2022 at 2:04 PM, TPC said:

@DXB

 

C driver to C driver,

My #3 & #4 cylinders run warmer in climb, then switches to #2 & #4 in cruise. I haven't had trouble managing the CHTs, even with surface temps +100. My typical initial climbs are 110-120 mph IAS - WOT - 2600rpm - 18-20 gph

I'll provide some further data for benchmarking. Hope it helps.

Mods:

• Lasar partial cowl closure
• Power Flow exhaust
• Surefly SIM <--saves 1 gph with +20 CHT@8500
• 10-4164-1 Carb
• Challenger air filter

JPI Data:

• 8500 ft - WOT(just off MP movement) - 2500 rpm - 8.5 gph - 147 kts TAS

Interesting. Your configuration is very similar to mine (richer carb, Surefly SIM, Powerflow, LASAR cowl closure). Also you have the same engine monitoring system - BTW I routinely see 18gph on takeoff but not 19 or 20.  The only major difference is your adjustable cowl flaps vs. my fixed ones.  I also have a Donaldson air filter vs. your Challenger and a different system for dumping waste carb heat air, but I can't see how that would explain anything. The OATs don't seem to be the critical determinant for me - things in climb actually got a bit better for me recently with warmer temps - making me think the extra power with the cold dense air was a major contributor to the high CHT on #4 in climb.  

I do think there is a basic issue with the design here, with #2 and #4 getting less airflow in cruise - that may be accentuated on my setup vs. yours since your #3 is hotter than your #2 in climb.  I wish I could figure out why. 

Interestingly, since getting the Powerflow I basically haven't been able to use 2500 rpm in cruise at any altitude (unless I want to burn 13gph to keep it cool). But if I do try to use it, I easily see TAS in the mid to high 150s (kts) !!  I routinely use 2300-2400 /near WOT at altitudes like yours (8500), ~8-8.5gph, to get the same airspeed you describe, maybe even a bit faster, and still often see CHTs on #2/#4 in the 395-415 range.  If I choose to burn 10gph at those MP/rpm settings, my speed is solidly at 150kt and above - I think the variable timing of the Surefly gets some credit for that.  

For some reason, I think part of the issue may be that my engine making a ridiculous amount of power for an O-360, and its cooling capability wasn't designed for it.  We've checked and double checked timing and retarded both sides 1-2 degrees from 25, but I saw minimal improvement 

 

[carusoam]

Next step…

Improved cooling by cowling re-design….

That project is making headway…

With a Mooney front end on wheels….

See SabreMech….

-a- 

[TPC]

@carusoam

Yes, so many variables with a carburetor.........

 

@DXB

I can't image not being able to use the entire RPM range in cruise due to CHT temps. Really strange....

Revisiting the picture below, do you have a upper baffle rubber seal across the entire cowl opening? I'm not sure if the doghouse design changed in the later years, but on mine a rubber seal hides all the sheet metal showing in your picture. Without the seal on mine, incoming air would route above the doghouse.

 

PS. We could start a whole new (4th or 5th) thread regarding TAS...haha

 

TC

 

 

 

[carusoam]

Proper seals at the front of the dog house are a must…

They often get forgotten when installing new starters and alternators…

I think the one missing above is called the lip seal?

We have a seal guy around here for that…

Best regards,

-a-

[chriscalandro]

I’ve been doing a lot of flying out TRM with days over 100degrees. Last time I was there was a check ride which we couldn’t really start the flying portion of until we got some altitude and the temps started to settle. 
 

sitting on the ground my CHTs at TRM will get to 400 and if I don’t do things fast enough I’ll start to get some bubbling gas bubbles through the carb. 
 

TRM I have to climb out every shallow to keep temps below 430. I do t have this problem at KPOC on similarly warm days. The DA will make a huge difference here. When I was based at DVT I didn’t see 400 very often. 
 

i miss the days of flying around with just one gauge on one cylinder with a red mark on it. I like my engine monitor, but I also like being blissfully unaware of the heat my cylinders are producing. 

Edited April 28, 2022 by chriscalandro

[47U]

On 4/23/2022 at 9:07 AM, DXB said:

For some reason, I think part of the issue may be that my engine making a ridiculous amount of power for an O-360, and its cooling capability wasn't designed for it.

Reviving the thread… 

Have you gained any improvement in your CHTs?  After rereading the thread, Paul Loewen says that the oil cooler experiences reverse airflow, so a plenum on the backside of the oil cooler to exit air out of a set louvers installed in the side cowl might actually diminish the amount of airflow through the cylinder fins.  (Yes, it took me only 7+ months to realize that might be the case.) 

As an aside, I reached out to SureFly tech support recently and they said that the magneto cooling tube (off the top of the doghouse) can be removed.  The SIM doesn’t need the cooling air.  I’m not sure if your SIM replaced the left or right mag…. perhaps something worth discussing with your A&P/IA.

One last thought, if you have a Concorde RGM (sealed) battery, that probably doesn’t need the same positive airflow as the flooded battery the battery box was designed around.  I’m thinking that the battery box drain tube is subjected to a Venturi effect in the cowl flap exit, so battery gets enough air circulation through the battery box cover.  If the vinyl tube connection between the baffle and battery box is removed, there’s potentially additional airflow into the battery box.  Plug the tube out of the #4 baffle and the air that was going to the battery box is now going down through the cylinder fins. 

[Jsno]

I thought about the Powerflow exhaust but after reading reviews about it I opted for a new original exhaust.  Knisely Welding makes one for about half of what a Powerflow runs.  Still putting the engine together but this spring will find out how well the system works.

[Pinecone]

If you duct the back of the oil cooler to a low pressure point (near the cowl exit) it may actually work better.  If the flow reverses, there are times when there is no flow.

[jetdriven]

On 4/9/2022 at 5:09 PM, DXB said:

Sadly already have the richer carb for the certified engine (there's a leaner carb, the leaner carb modified to match the richer version, and the richer version - the one i have) - can't get more than 18gph on it - the main jet can be reamed larger on the richer version, though not technically legal in the certified world.  

Sadly already retarded both sides to 23 (also not technically legal for the engine) - no much difference. If I retard it more, there may be a power dropoff...

The cowl flap modifications may be in my future - I have the fixed version on the '68 permanently set to 1.1" opening - no heim joints there...

We found a shop that will install a larger jet and They can put the fuel flow wherever you want it. And it’s legal. 
I’ve seen it a few times now if somebody installs either a power flow or an engine monitor on an engine with a power flow and find out it runs way to lean at  takeoff power, you need to supply more fuel because the exhaust scavenges better

[DXB]

On 12/3/2022 at 9:03 PM, 47U said:

Reviving the thread… 

Have you gained any improvement in your CHTs?  After rereading the thread, Paul Loewen says that the oil cooler experiences reverse airflow, so a plenum on the backside of the oil cooler to exit air out of a set louvers installed in the side cowl might actually diminish the amount of airflow through the cylinder fins.  (Yes, it took me only 7+ months to realize that might be the case.) 

As an aside, I reached out to SureFly tech support recently and they said that the magneto cooling tube (off the top of the doghouse) can be removed.  The SIM doesn’t need the cooling air.  I’m not sure if your SIM replaced the left or right mag…. perhaps something worth discussing with your A&P/IA.

One last thought, if you have a Concorde RGM (sealed) battery, that probably doesn’t need the same positive airflow as the flooded battery the battery box was designed around.  I’m thinking that the battery box drain tube is subjected to a Venturi effect in the cowl flap exit, so battery gets enough air circulation through the battery box cover.  If the vinyl tube connection between the baffle and battery box is removed, there’s potentially additional airflow into the battery box.  Plug the tube out of the #4 baffle and the air that was going to the battery box is now going down through the cylinder fins. 

Leaving the throttle out an inch at takeoff does result in cooler CHTs in climb, though still well above 400 frequently on #2 and #4, occasionally past 440, but never the 450+ I used to see - the improvement appears to result from better mixture distribution from the cocked throttle plate, despite a slight reduction in fuel flow from loss of the enrichment circuit.  Putting a still richer nozzle onto my richer carb, as @jetdriven suggests, would probably help further but I've been reluctant to do much more elective invasive work on my 1600 hr, 22 year SMOH engine.  I'll address the carb at overhaul at the very latest.  The carb doesn't explain the high temps I see at lower powers in cruise.  I think the difficult to manage temps on #2 and #4 leaned at lower power in cruise result primarily from the timing advance on the Surefly and not the Powerflow; I probably should just switch it back to fixed timing on the Surefly.  The combination of Surefly and Powerflow gives me an absurdly fast C model at my previous MP/RPM settings in cruise  (like 155-158kt), but I have to either pull back power or richen past 12gph to keep it acceptably cool, so it ends up being a zero sum game at best.  I basically see the same cruise speeds and slightly higher CHTs now at 22/2300 vs pre Powerflow/Surefly at 22/2500 (each at ~9.5gph, ~8000 ft).

Plugging the cooling tube on the Surefly (left side for me) is a great idea. I'll double check with Surefly and just do it if they say it's ok. 

I'm apprehensive about plugging the cooling tube to the battery box even with my sealed Concorde.  I imagine they moved to the tail in later models for very good reason, perhaps cooling being one of them?  The battery does have an operating range up to 131 F, but I have no clue how hot it gets in the box vs. how hot it would get if I plugged that cooling tube behind #4.  I'm also not sure the voltage regulator could compensate adequately for the higher temps (need to charge to lower voltage to avoid trashing the battery).

 

[kortopates]

We found a shop that will install a larger jet and They can put the fuel flow wherever you want it. And it’s legal. 
I’ve seen it a few times now if somebody installs either a power flow or an engine monitor on an engine with a power flow and find out it runs way to lean at  takeoff power, you need to supply more fuel because the exhaust scavenges better

Very true, i’ve helped many clients through this process with the engine monitor data to get the max FF increased.


Sent from my iPhone using Tapatalk

[Will.iam]

11 hours ago, DXB said:

Leaving the throttle out an inch at takeoff does result in cooler CHTs in climb, though still well above 400 frequently on #2 and #4, occasionally past 440, but never the 450+ I used to see - the improvement appears to result from better mixture distribution from the cocked throttle plate, despite a slight reduction in fuel flow from loss of the enrichment circuit.  Putting a still richer nozzle onto my richer carb, as @jetdriven suggests, would probably help further but I've been reluctant to do much more elective invasive work on my 1600 hr, 22 year SMOH engine.  I'll address the carb at overhaul at the very latest.  The carb doesn't explain the high temps I see at lower powers in cruise.  I think the difficult to manage temps on #2 and #4 leaned at lower power in cruise result primarily from the timing advance on the Surefly and not the Powerflow; I probably should just switch it back to fixed timing on the Surefly.  The combination of Surefly and Powerflow gives me an absurdly fast C model at my previous MP/RPM settings in cruise  (like 155-158kt), but I have to either pull back power or richen past 12gph to keep it acceptably cool, so it ends up being a zero sum game at best.  I basically see the same cruise speeds and slightly higher CHTs now at 22/2300 vs pre Powerflow/Surefly at 22/2500 (each at ~9.5gph, ~8000 ft).

Plugging the cooling tube on the Surefly (left side for me) is a great idea. I'll double check with Surefly and just do it if they say it's ok. 

I'm apprehensive about plugging the cooling tube to the battery box even with my sealed Concorde.  I imagine they moved to the tail in later models for very good reason, perhaps cooling being one of them?  The battery does have an operating range up to 131 F, but I have no clue how hot it gets in the box vs. how hot it would get if I plugged that cooling tube behind #4.  I'm also not sure the voltage regulator could compensate adequately for the higher temps (need to charge to lower voltage to avoid trashing the battery).

 

Just buy a blue tooth temperature sensor and zip tie it to the location you want to know the temperature of and go fly. The bluetooth link to your phone will reach to you in the cabin and you can see for yourself in real time what temperatures the battery is seeing and what temperature is there after  you plug up the hole. Make sure you do some slow flight / high angles of attack flights or just extended climbs to give that compartment time to stabilize as that really heats up things in the cowl. 

[cliffy]

Those who have an Interav alternator you will see that the air flow is also from inside to outside by the way the fins on the fan are set up. 

Talked to an Interav engineer about it and they designed it that way.

ENGINE COOLING IS A PRIME FACTOR IN CERTIFICATION so any design changes to that  can affect certification  status. Something not to be taken on a whim or "minor mod" IT DON'T QUALIFY THAT WAY

Sealing the dig house is essential to cooler temps. All around the engine case and accessories in addition to the cylinders.

Double check the case seals and the alt/starter seals. Are they hard as a brick? Are they touching the affected parts?

Check to make sure you have the "inter-cylinder" baffles along with tight outer bands with the small threaded rods holding them fore and aft. 

The cowl lip seals are as mentioned a big area of cooling air lose if not sealed correctly after every cowl removal 

Check each thermocouple in boiling water to see if it reads correctly or hot oil with a candy thermometer (350')

I have no problems on my D except when over a 100 at my airport altitude (4000') Then only after a couple 1000 feet I have to accelerate 

to 110-120 and MAYBE pull back the cruise power (2500 and WOT) for a few minutes and even then never above 400