M20C Engine Baffle Question

[MarkC]

I have a question about the engine baffle on my M20C.  Right behind the #3 cylinder on the back side of the baffle there is a round ~1 inch diameter opening that has a flange where it looks like you would attach a vent tube.  But, mine has the opening capped with a plastic cap held in place with a hose clamp.  Should that flange have a length of scat tube attached that runs down to the bottom of the engine compartment for venting?  It sure seems like it would help reduce the engine temps on #3.  

Any advice appreciated.

 

[Sabremech]

43 minutes ago, MarkC said:

I have a question about the engine baffle on my M20C.  Right behind the #3 cylinder on the back side of the baffle there is a round ~1 inch diameter opening that has a flange where it looks like you would attach a vent tube.  But, mine has the opening capped with a plastic cap held in place with a hose clamp.  Should that flange have a length of scat tube attached that runs down to the bottom of the engine compartment for venting?  It sure seems like it would help reduce the engine temps on #3.  

Any advice appreciated.

 

I think that should have a scat hose connected to the mechanical fuel pump shroud. 

[Bob_Belville]

2 minutes ago, Sabremech said:

I think that should have a scat hose connected to the mechanical fuel pump shroud. 

That's what my E model has.

[Skates97]

Is it at the top back corner of the doghouse? 

4 hours ago, Sabremech said:

I think that should have a scat hose connected to the mechanical fuel pump shroud. 

I would love to see a picture of that, I think mine is going down to the carb heat box? 

[DXB]

Like @MarkC, I have a '68C.  I'm not aware of anything coming off the back of the doghouse behind #3 that cools the engine driven fuel pump - nor could I find something like that  diagrammed in the parts manual.  I just have the air intake hose for the carb heat at that location, as @Skates97 describes.   

After some digging a while back, I had found that the hose to the cooling shroud for the engine-driven fuel pump was routed from this little circular intake on the front of the bottom cowl, just above air filter (not my plane pictured). My hose and shroud for the pump were long missing when I got my plane, so I just sealed the hole.  It would be game to revisit that system and whether it is really necessary.   I also just looked for that diagram in the parts manual too and could not find  -  maybe I'm wrong - I could have sworn that I saw it diagrammed somewhere before.  

Of course @Sabremech knows WAY more about this stuff than I do  -  I could be totally wrong here...

 

[Sabremech]

13 minutes ago, DXB said:

Like @MarkC, I have a '68C.  I'm not aware of anything coming off the back of the doghouse behind #3 that cools the engine driven fuel pump - nor could I find something like that  diagrammed in the parts manual.  I just have the air intake hose for the carb heat at that location, as @Skates97 describes.   

After some digging a while back, I had found that the hose to the cooling shroud for the engine-driven fuel pump was routed from this little circular intake on the front of the bottom cowl, just above air filter (not my plane pictured). My hose and shroud for the pump were long missing when I got my plane, so I just sealed the hole.  It would be game to revisit that system and whether it is really necessary.   I also just looked for that diagram in the parts manual too and could not find  -  maybe I'm wrong - I could have sworn that I saw it diagrammed somewhere before.  

Of course @Sabremech knows WAY more about this stuff than I do  -  I could be totally wrong here...

 

The little one out front went to the generator or alternator if you upgraded ( at least it did on my 66C ).

Edited May 5, 2019 by Sabremech

[Skates97]

2 minutes ago, Sabremech said:

The little one out front went to the generator or alternator if you upgraded ( at least it did on my 66C ).

Yes, on mine it is a short little hose from that one on the front to the generator. 

[DXB]

25 minutes ago, Sabremech said:

The little one out front went to the generator or alternator if you upgraded ( at least it did on my 66C ).

 

21 minutes ago, Skates97 said:

Yes, on mine it is a short little hose from that one on the front to the generator. 

Huh.  Thanks - I clearly had the wrong idea on that one.  

Would love to see pic of the cooling system from the engine driven fuel pump I'm missing, and also figure out if it is important or not.  

[Skates97]

15 minutes ago, DXB said:

Would love to see pic of the cooling system from the engine driven fuel pump I'm missing, and also figure out if it is important or not.  

I would as well. 

[Sabremech]

Mines not connected to the fuel pump housing and it’s never been an issue. 

David

[Guest]

Some vents on the back baffles for magneto cooling, some dog house baffles took mag cooling off the top cover, some fuel pump cooling off the back baffle as well.

Clarence

[MB65E]

65e mine has an exit  behind #4 not #3 for the fuel pump scat cooling hose. 

-Matt

[MarkC]

Here's a picture of the opening.  The parts manual shows it and notes it as "Tube, Blast".  The cap has been removed as I took the picture.

 

[DXB]

@MarkC  Here's the schematic for that part of the doghouse from '68 C parts manual.  The only hole behind #3 cylinder is labelled 55,  listed as "connection, air duct."  I'm confident that is the air intake for the carb heat and must have a scat hose that goes to the muffler shroud.  However my connection at that site is angled down by 90 degrees, unlike yours. Note the baffling for the E and F models (a couple pages later in the manual) does have a hole labeled "Tube, blast."   I'm guessing your baffling was swapped at some point for the baffle from an E or F model? But then where is your carb heat air intake??

[MarkC]

DXB, you are correct with the parts manual reference.  I was looking at the wrong model in the parts manual.  So it is 55 in the parts manual that I am referring to.  I will have to check the carb heat connection on mine and report back.  I am certain it is connected someplace because it works!

[mike20papa]

  On my A model - that always runs cool with under 375F cyl head temps - has a 2" duct at the taxi/landing light bucket that feeds the exhaust system heat exchanger that feeds carb heat or cabin heat.  NO HOLES in dog house for cooling except for two 1/2" blast tubes for the mag.s - mounted on top of the house.  I also have the 1" blast tube that runs from front of lower cowling back to the fuel pump.

The entire design of this system got lost when Mooney dropped the dual pipe exhaust and went to the single pipe - I've had both.  The dual pipe system is way superior.  My opinion.  Joe

 

Again - sorry for the inverted photo ?!

Edited May 7, 2019 by mike20papa
photo

[Skates97]

3 hours ago, mike20papa said:

  On my A model - that always runs cool with under 375F cyl head temps - has a 2" duct at the taxi/landing light bucket that feeds the exhaust system heat exchanger that feeds carb heat or cabin heat.  NO HOLES in dog house for cooling except for two 1/2" blast tubes for the mag.s - mounted on top of the house.  I also have the 1" blast tube that runs from front of lower cowling back to the fuel pump.

The entire design of this system got lost when Mooney dropped the dual pipe exhaust and went to the single pipe - I've had both.  The dual pipe system is way superior.  My opinion.  Joe

 

Again - sorry for the inverted photo ?!

 

Here you go.

[carusoam]

Looks like a brand new A! 

MP, gotta post more pics!

Best regards,

-a-