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Thread: Interesting extreme power loss with carb heat in Wren Converted C182

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    Alex Clark's Avatar
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    Interesting extreme power loss with carb heat in Wren Converted C182

    I was with the new owner of a Wren 460 yesterday. ( a C-182 with extreme stol wings and canards)
    Because the weather was all misty I told him to give the carb heat a few seconds.

    Well we went from 2350 squared to 1700 and choking real fast. The nose dropped and it was interesting.

    So today the new owner took it to a local IA ( non-pilot) who is thinking it is because of the small 3 inch scat tubing being sucked upon by a O-520 engine. I think my O-520 uses 3 inch tube for the carb heat set up and it does not do this....

    A call to the previous owner revealed that he tried the carb heat once 3 years ago and never tried it since then...

    I thought it might have been a messed up vent flap or maybe somebody left a rag in the scat tube during an annual.

    Anyway, no cure so far... It also has an electronic ignition on one side...

    I will post more info about that highly modified C-182...

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    skywagon8a's Avatar
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    Quote Originally Posted by Alex Clark View Post
    ...Because the weather was all misty I told him to give the carb heat a few seconds.

    Well we went from 2350 squared to 1700 and choking real fast. The nose dropped and it was interesting.

    So today the new owner took it to a local IA ( non-pilot) who is thinking it is because of the small 3 inch scat tubing being sucked upon by a O-520 engine. I think my O-520 uses 3 inch tube for the carb heat set up and it does not do this......
    What happened when you tested the carb heat during the before takeoff run up?
    What had the manifold pressure done prior to pulling the carb heat on? Had it gone down indicating that there was ice?
    The rubber coupling hose between the engine and the air box on 185s has internal wire reinforcement which prevents it's collapsing. When running up a 185 with the cowl off and that rubber coupling still in place it can get sucked into the intake giving the same results that you describe.
    Perhaps the scat coupling on that Wren is not reinforced against collapse? Get it fixed.
    N1PA

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    It sounds like he may have had ice. Is the drop consistent?

    Where's the source of heat? The drop from a heat robber on a riser is way less than the drop from an outlet in the muffler shroud. Because it's not what you're used to doesn't mean its broken.
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    www.SkupTech.com mike mcs repair's Avatar
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    Muffler cracked. Feeding exhaust into carb when carb heat on....


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    Alex Clark's Avatar
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    For the above questions:

    It acted OK on the ground but was more drop than I am used to, ( he has a digital tach which is kinda sensitive) We did it three times in flight. Even after having it applied for 15 seconds, then back on again after a 30 second break, it did the same thing.

    Not my plane, but I want to steer him in the right direction since he is a 1st time owner and a nice guy.
    The IA who thought nothing was wrong, also told him that he did not need to worrying about carb ice around here....So I had to repeat the how carb ice is made lesson.
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Alex Clark View Post
    For the above questions:


    The IA who thought nothing was wrong, also told him that he did not need to worrying about carb ice around here....So I had to repeat the how carb ice is made lesson.
    pull muffler shroud inspect muffler can....

    you really need to find a new mechanic....

  7. #7
    Alex Clark's Avatar
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    I did.
    I hope new owner will too.

    Is there any way to do a quick and dirty with a reversed shop vac, two girls from the strip club and a rubber chicken suit?

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    As everybody else said...cracked exhaust.

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    Obstruction in the air intake hose going to the muffler? Once in a while I find a C150 with a bunch of wet leaves and crap stuck in that hose.
    You can't get there from here. You have to go over yonder and start from there.
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    How many of you have Cessnas that draw carb heat from the muffler?

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    Check for loose screws on the carb float bowl
    DENNY

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    skywagon8a's Avatar
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    Alex,
    I would accept up to 150-200 rpm (200 would be high, 150 better) drop when the Carb heat is applied as long as it is reasonably smooth. And stewart is right, if this is the same system as a 180 the carb heat is taken from a baffle around the exhaust pipe. The muffler has nothing to do with it. IF there is a leak or broken clamp at that joint in the exhaust pipe it could be sucking exhaust gasses which could give an excessive and possibly rough drop.
    A 650 rpm drop in flight sounds more like the scat tube collapsed restricting the air flow. Or something else restricting somewhere in that tube like a rag or birds nest.
    N1PA

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    I may be wrong, but I don’t recall any O-520 engines, aren’t they all IO-520? If so, it shouldn’t have carb heat. Maybe alternate air, but not carb heat.


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    Pponk (that STC recently was sold, by the way), Kenmore Air, and Texas Skyways all have offered carb converted 520s for many years. Very common engines in 180s and 182s.

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    Quote Originally Posted by stewartb View Post
    Pponk (that STC recently was sold, by the way), Kenmore Air, and Texas Skyways all have offered carb converted 520s for many years. Very common engines in 180s and 182s.
    O-470-50?


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    www.SkupTech.com mike mcs repair's Avatar
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    Carb heat door/flapper broke free from actuator rod??

    It’s time to pull the cowling and look


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    Quote Originally Posted by dgapilot View Post
    O-470-50?


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    That's Pponk's term. Kenmore and TS call them O-520s, as do the vast majority of Pponk owners.

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    Quote Originally Posted by stewartb View Post
    That's Pponk's term. Kenmore and TS call them O-520s, as do the vast majority of Pponk owners.
    TS starts with a 520, Pponk starts with an o-470 and puts 520 parts on it...

    Now, back to the original post- I have heard lots of good answers. Two stick out: Find a new mechanic, and pull off the cowl and inspect from inside the heat muff to the carb.

    I bet it is easy to fix.

    Watch the stripper with the rubber chicken, when applied near the Wife unit, it will cost you way more than you want to pay.
    I don't know where you've been me lad, but I see you won first Prize!
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    Pponk swings both ways. You can start with an O-470 or an IO-520. Or a bastard like mine, a 470 case married with a 520 crank. They all end up in the same place. 520 cubic inches with a carb that likely needs the main jet reamed!
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by stewartb View Post
    Pponk swings both ways. You can start with an O-470 or an IO-520. Or a bastard like mine, a 470 case married with a 520 crank. They all end up in the same place. 520 cubic inches with a carb that likely needs the main jet reamed!
    but, to get the higher TBO, you MUST start with a 470.....

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    Quote Originally Posted by Alex Clark View Post
    I was with the new owner of a Wren 460 yesterday. ( a C-182 with extreme stol wings and canards)

    A call to the previous owner revealed that he tried the carb heat once 3 years ago and never tried it since then...
    This is a comment that scares me, the problem is inherent in this build and no one has seen a need to fix it over recent years.

    I find it hard to think a cracked exhaust would go un-detected for year after year.

    Are the intake hoses Scat or Skeet?
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    In Alex's scenario the first "test" I'd have done would have been to lean the mixture to see if/how RPMs recovered.
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    skywagon8a's Avatar
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    Quote Originally Posted by stewartb View Post
    In Alex's scenario the first "test" I'd have done would have been to lean the mixture to see if/how RPMs recovered.
    After this? "Well we went from 2350 squared to 1700 and choking real fast. The nose dropped and it was interesting."
    The first thing is to undo what he just did. Then to declare "Sum Ting Wong"​ and head for the airport.
    N1PA
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    I read what he said, including
    Even after having it applied for 15 seconds, then back on again after a 30 second break, it did the same thing.
    . Apparently they knew failure wasn't imminent. With that established I'd have explored the mixture.

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    Canard is creating a vortex at the carb heat inlet. Can't believe previous owner went 3 years not needing carb heat. Seriously You better get it fixed.

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    Alex Clark's Avatar
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    STEWARTB:

    A. The initial power loss and nose drop was 15 miles from the airport with a limited ceiling. ( 1,000 ft)

    B. The 15 second repeat test were done after I returned to the airport at max speed and was in a better ceiling area 1,500 feet over the runway. Followed by landing.


    UPDATE:

    One of the scat tubes had the wires cut out far too much and the soft part was not pulled up far enough into the metal tubing. Thus collapsing under suction.
    After cutting off some excess and sliding it further up before re-securing it, the rpm loss was reduced to 150 rpm on the ground and 175 to 200 in flight depending on throttle settings. At low power setting like on final it now only drops 150 rpm.

    Further investigation to follow just in case....
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  27. #27
    RaisedByWolves's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    but, to get the higher TBO, you MUST start with a 470.....
    I thought the skyways 0-520 was a high tbo. But only if they overhaul it in house. Adds a different oil sump drain or something.


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    Alex Clark's Avatar
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    Took it out again in better conditions today:
    Carb heat now results in much less RPM loss, however it still seems rather rough while using heat. A sort of burbling feeling.
    So I did the mixture leaning and it did smooth it out somewhat. So it is excessively rich.

    I have been noticing that the fuel burn it this carbed 520 is more than my carbed 520.
    Using the same manifold and RPM setting this one goes from 15.1 to 17.8 per hour
    Mine will get down to 13.0 to 17.0

  29. #29
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by RaisedByWolves View Post
    I thought the skyways 0-520 was a high tbo. But only if they overhaul it in house. Adds a different oil sump drain or something.


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    I’m referring to the pponk


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    Quote Originally Posted by Alex Clark View Post
    Took it out again in better conditions today:
    Carb heat now results in much less RPM loss, however it still seems rather rough while using heat. A sort of burbling feeling.
    So I did the mixture leaning and it did smooth it out somewhat. So it is excessively rich.
    I have been noticing that the fuel burn it this carbed 520 is more than my carbed 520.
    Using the same manifold and RPM setting this one goes from 15.1 to 17.8 per hour
    Mine will get down to 13.0 to 17.0
    There are various sizes of main jet the 0-520 can have. I had the same problem and knopp recommended a smaller main jet. My original fuel flow at full power full rich was 30gph and would run super rough with carb heat. I now get 22gph and it behaves normal.
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    Go see what the leaning authority is at cruise. That's the test that matters. It sounds like you should test yours as well.

    What power settings are you using to see 13 gph? I'm generally at 24/2400 and leaning to 16 gph makes my engine happy. If I leave it full rich it's just over 19 gph at that power. Like most Pponk owners I know it took work to get more fuel. Pponk's carb specs were way too lean.

  32. #32
    Alex Clark's Avatar
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    What power settings are you using to see 13 gph?
    20 inches , 2200 rpm, leaned to temps, at around 8,000 ft. That is my slow over the ice-field setting for flight-seeing folks to take photos.

    My 180 hits 22 gph on take-off.
    around 17 gph at 25/2500
    16 at non-leaned 23/2350
    15 gph at a leaned 23/2350

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    What’s the EGT spread between full rich and peak at cruise power? Your flows sound like mine used to be. No criticism, just interested in the fuel flows of different PPonks. Mine had carb work several times after the basic mod trying to improve fuel flow and engine temps. Fortunately a mechanic friend familiar with Pponk fuel issues sorted it out. Now the temps are so even you’d think it was injected.

    Does yours make ice?

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