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Exhaust pipe orientation


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In Dan's thread about the Sensorcon and CO readings there was some discussion about levels people have seen. Rather than sidetrack his thread I started a different one.  I made mention that I sometimes see numbers in the 40-50's and sometimes it's 2-3 so I think it may have to do with the direction of the wind. Always once established in cruise it drops to zero or 1. Today while taxiing with the wind behind me I saw readings in the upper teens but once I turned around with the wind at about 10 o'clock for run-up the numbers dropped. 

I have checked for places I thought I could be getting leaks from and also recently replaced the old door seal with no changes in readings. I have wondered if the direction my exhaust pipe is oriented is causing some issues. I've looked at other Mooneys and haven't seen one with a pipe like mine has. 

20180218_165516.thumb.jpg.238ef39b84660b56d0c7a01d55c4553e.jpg

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Draw a line directly up from the exhaust pipe.

Do you have an air vent mounted in front of the door?

In that vent is there a tube that feeds the back of your radios for cooling them?

That would be a way for CO to get easy access while on the ground...

There is not a tight seal for our cabins.  Especially on the older models...

Another place to look, is further back, where the wing and the fuselage come together.  If you haven’t seen the duct tape that was used to seal the cabin from the outside.  There are some real gaps there as well, hiding under the molding....

PP thoughts only. Not a mechanic...

Best regards,

-a-

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19 minutes ago, carusoam said:

Draw a line directly up from the exhaust pipe.

Do you have an air vent mounted in front of the door?

In that vent is there a tube that feeds the back of your radios for cooling them?

That would be a way for CO to get easy access while on the ground...

There is not a tight seal for our cabins.  Especially on the older models...

Another place to look, is further back, where the wing and the fuselage come together.  If you haven’t seen the duct tape that was used to seal the cabin from the outside.  There are some real gaps there as well, hiding under the molding....

PP thoughts only. Not a mechanic...

Best regards,

-a-

There is a vent there which had a duct that went to cool the ADF. When the ADF was removed the duct was also removed and the vent was plugged so that's not it. I will have to check where the wing and fuselage come together. 

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Mouse socks aren’t very air tight... areas where the landing gear comes into the fuselage...

Nose gear has some penetrations as well...

Rudder pedals and the J bar all have large holes around them...

The trim wheel is mounted in the floor board.  

The exhaust enters the area below the floor board a little easier than expected.  See the first pic above...

check all the openings for CO levels while on the ground.  

On the ground, the exhaust fumes are measured in hundreds of cubic feet per minute... the plane is getting surrounded in exhaust, unless the wind is doing a nice job of sending it towards the tail....

For Best results, point into the wind...

PP thoughts only, not a CFI.

Best regards,

-a-

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Milotron posted a pic of the door on his plane with the interior panel removed.  Sunshine can be seen entering through where the door handle comes through the sheet metal.  There is an old rubber seal there that is worth looking into.  Too old, it lets a lot of daylight in...

right next to that is the door lock.  No sunshine, but no seal either...

Best regards,

-a-

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My guess would be around the rudder pedals, check the sheet metal in the exhaust cavity, if they don't fit tight exhaust can get between the floor and belly and its open behind the rudder pedals. Might be able to seal the seam with aluminum tape?

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Thank you all for the ideas, that gives me some more things to check. It isn't terribly concerning because the levels don't get to where it is a real problem and the levels always drop as the climb progresses and down to nothing or almost nothing in cruise, but I would still like to see the initial levels lower.

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I've been told when the nose gear landing door opens in flight a venturi effect occurs between the tail pipe exhaust and wheel well.  In my plane I can smell exhaust fumes when lowering the landing gear prior to landing.  Once on the ground the exhaust smell clears out.  I've never notice an increase in my CO detector.  My CO detector is attached above my compass with Velcro.  A few years ago I sent my exhaust system to Dawley Aviation to have it overhauled.  My tail pipe was shot and I ask Dawley to make my new tail pipe longer thinking it would prevent the exhaust smell.  Dawley explained to me they had to duplicate my tail pipe to original.  I noticed a few other Mooney's with different lengths of tail pipes.  I always wondered if a longer tail pipe would make a difference.

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23 hours ago, bluehighwayflyer said:

I’m surprised you don’t have a second tailpipe clamp.  My ‘78 J’s tailpipe is very similar to yours and in addition to the clamp on the firewall it has another one about midway back. I’m glad it does, too, because after 12 trouble free years I discovered the firewall clamp to be broken during my most recent annual inspection. 

Jim

Do you have a picture? Maybe I need another clamp?

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