Page 2 of 3 FirstFirst 123 LastLast
Results 41 to 80 of 97

Thread: Exhaust Advice

  1. #41
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Gordon did you place the restriction on the air inlet to the muffler heat shroud (a single 2”) or the outlet, just past the heater and carb heat connections (two 2” outlets?). If it was the outlet what percentage of the outlet did you restrict?
    I placed the restriction on the inlet to the carb air side of the muffler shroud. It helped considerably, but carb heat is still not as aggressive as I'd like. In difficult conditions, i.e. low OAT, I pull carb heat at cruise power, then immediately reduce power - sometimes to idle - to get the carb temp up. I have an EI carb temp probe and readout. I want to get 40F, when I pull carb heat.Click image for larger version. 

Name:	Carb Heat Restrictor Plate.jpg 
Views:	77 
Size:	119.0 KB 
ID:	41400
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  2. #42
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,463
    Post Thanks / Like
    Most heat at low airspeed full power.
    N1PA
    Likes DENNY liked this post

  3. #43
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    Carb air passes over the exposed end of the muffler can, hopefully, and over the #2 and #4 exhaust pipes going into the muffler. Heat ribbons will not increase the temp of the carb air as the carb air does not pass over that portion of the Sutton muffler. That is my recollection and I will confirm it when I get to the airplane.

    To anyone with a carb temp probe and any exhaust system, I am interested to know what your temp probe display does with the application of carb heat. Up? Down? No change? PM’s welcome, Jim
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	AA1B769F-AB1B-476E-8D98-4DA51A7651F6.jpeg 
Views:	64 
Size:	190.7 KB 
ID:	41402  
    Last edited by cruiser; 02-09-2019 at 07:36 AM. Reason: Photo added

  4. #44
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Quote Originally Posted by skywagon8a View Post
    Most heat at low airspeed full power.
    Pete, that's correct, but incomplete - only half of the process. First, note the difference between 'heat' and 'temperature'. Heat is energy, and temperature is a measure of energy per unit mass.

    So with greater airflow through the muffler shroud, i.e. more air mass needing its temperature raised, more heat is required to raise the temperature of the air. For a given available heat from the muffler surface, greater temperature rise will occur with reduced airflow.

    For that reason, the greatest temperature rise is obtained by running the engine hard, pulling carb heat and promptly reducing power to idle while the muffler is still hot. If you have a carb temp gage, give it a try.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Thanks Jonnyo thanked for this post

  5. #45
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    CAR 3 suggests:

    § 3.606 Induction system de-icing and antiicing
    provisions. The engine air induction
    system shall incorporate means for the
    prevention and elimination of ice accumulations
    in accordance with the provisions in this section.
    It shall be demonstrated that compliance with the
    provisions outlined in the following paragraphs
    can be accomplished when the airplane is
    operating in air at a temperature of 30° F, when
    the air is free of visible moisture.
    (a) Airplanes equipped with sea level
    engines employing conventional venturi
    carburetors shall be provided with a preheater
    capable of providing a heat rise of 90° F. when
    the engine is operating at 75 percent of its
    maximum continuous power.

    Might be a reason for that spec.

    Gary
    Thanks Gordon Misch, cruiser, Beaverpilot thanked for this post
    Likes DENNY, cruiser liked this post

  6. #46
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    90 deg - wow! My STC'd installation won't come even close to that.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Thanks cruiser thanked for this post

  7. #47
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    Quote Originally Posted by Gordon Misch View Post
    90 deg - wow! My STC'd installation won't come even close to that.
    How's that noted: "Trust but verify"

    Edit: Here's an exhaustive discussion of carb ice (good pun, eh?). Notice the strong suggestion not to move the throttle closed if icing is suspected and the reason why it may cause engine stoppage:

    http://www.whittsflying.com/web/page...e_and_Heat.htm

    Gary
    Last edited by BC12D-4-85; 02-09-2019 at 02:56 PM.

  8. #48
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    Quote Originally Posted by Gordon Misch View Post
    Pete, that's correct, but incomplete - only half of the process. First, note the difference between 'heat' and 'temperature'. Heat is energy, and temperature is a measure of energy per unit mass.

    So with greater airflow through the muffler shroud, i.e. more air mass needing its temperature raised, more heat is required to raise the temperature of the air. For a given available heat from the muffler surface, greater temperature rise will occur with reduced airflow.

    For that reason, the greatest temperature rise is obtained by running the engine hard, pulling carb heat and promptly reducing power to idle while the muffler is still hot. If you have a carb temp gage, give it a try.
    Note that your carb heat air does not flow under the muffler shroud with a Sutton exhaust. At least not around the muffler can in the way most of us expect it to. The shroud is extended out over the end of the muffler where the #2 and #4 exhaust pipes enter. The carb heat air passes by this area as it is drawn into the carb heat box by engine vacuum. Perhaps that might help explain your experience in post #46

  9. #49
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Location
    Graham, TX
    Posts
    17,995
    Post Thanks / Like
    This topic kind of threw me off. For one I don't get much carb ice in Lycomings. I only pull mine on pre-flight and when humid which isn't often around here. Also I get quite an rpm drop from my Sutton exhaust when I pull carb heat. I have been around airplanes long enough to know that there is a lot of PFM between two airplanes that appear exactly the same. For this reason I called Brian Sutton and asked him what he knew about it. Having maintained a couple of Grumman Tigers many years ago I knew he had pretty much used that design for this exhaust only tweaking it slightly for clearance with the cowl so that he could install the prop governor for his constant speed prop STC. I did not realize that the exhaust system is actually an Elano 100 design and used on almost 60 different fixed wing and helicopters. Brian did add the end plate to the muffler can where carburetor heat is drawn. He recalls having had one call with this issue. He did say there is a lot more carb heat from the stock Super Cub exhaust system. Brian enlightened me to some things about the system I had not thought about. The cold wetter air tends to get drawn to the rear cylinders and the drier air gets drawn down between the front cylinders and into the carb heat baffle. Something I had to think about and never realized.

    My Dad and I talk a lot about mechanical things. He is a retired mechanical engineer and is the reason I got interested in how things work and fixing stuff. He lives in Memphis which has a fairly humid climate. He installed the Sutton exhaust on his Clipper via a field approval several years ago to get away from the exhaust AD and to get the muffler off the firewall and free up engine space. When he and I got caught in the arrival procedure gauntlet at Oshkosh this year, I was in my brothers Clipper, he was in his, we diverted to New Holstein to regroup. When we departed New Holstein he noticed I was running off and hiding from him which is usually not the case. This is when he noticed he had left his carb heat on. On our return triphome he didn't feel like he was making normal power and temps (UBG16 engine monitor and FP5L fuel flow) so we landed to check things out. We figured out his carb heat flapper valve was slightly open so we readjusted. I post this just to establish that in his application with a rear oil cooler and 160 hp O-320 he seems to be getting carb heat. He does not have a carb temp gauge.

    Now, another piece of this puzzle recently when I was helping a friend order a Electronics International CGR30P engine monitor for his Cessna 180. We were discusssing the carb temp option and he told me about the inaccuracies of carb temp gauges as ooposed to carb ice detectors such as the ARP gauge that detects actual ice crystals. https://www.aircraftspruce.com/catal...clickkey=25900 This was something else I was not aware of and made for some interesting reading. I do not know the answer to Jim and Gordon's issues but with all the information I have gathered the one question I have is have you actually gotten carb ice and if you did would the system not melt it?

    Sorry if I have rambled but I have been sick for a week and still feel a bit impaired so some of this might not make any sense.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
    Likes nightflyer liked this post

  10. #50
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,463
    Post Thanks / Like
    Quote Originally Posted by Gordon Misch View Post
    Pete, that's correct, but incomplete - only half of the process. First, note the difference between 'heat' and 'temperature'. Heat is energy, and temperature is a measure of energy per unit mass.

    So with greater airflow through the muffler shroud, i.e. more air mass needing its temperature raised, more heat is required to raise the temperature of the air. For a given available heat from the muffler surface, greater temperature rise will occur with reduced airflow.

    For that reason, the greatest temperature rise is obtained by running the engine hard, pulling carb heat and promptly reducing power to idle while the muffler is still hot. If you have a carb temp gage, give it a try.
    Then the heat stops and the carb refreeze, now what?
    N1PA
    Likes TurboBeaver liked this post

  11. #51

    Join Date
    Feb 2004
    Location
    Mt.
    Posts
    1,271
    Post Thanks / Like
    Quote Originally Posted by Steve Pierce View Post
    Hmm, I have not heard of this issue. Of course it rarely gets in the 20s and when it does and I am flying it is pretty clear and I don't remember pulling carb heat. Has anyone asked Brian Sutton about this? I wonder about closing the end of the shroud and putting pressurized air to it.
    Steve, ask S2D about carb ice and cabin heat in 37L. I remember it trying to quite one day with a little snow in the air when no other cub flying in close proximity was havin any trouble. I think he fixed it but don’t remember how.
    Dave

  12. #52

    Join Date
    Apr 2017
    Location
    ND
    Posts
    51
    Post Thanks / Like
    One of the crashes of one of my Cub’s previous lives was due to carb-ice - noticed shortly after take-off. Application of carb heat put the cub into the trees.

    I dont know much about it, but a mechanic told me there was a carburetor/0320 specific combination that was referred to as the “ice maker.”

    I don’t think I have ever experienced carb ice, and mine is no longer the so called ice maker combo.

    I can comment that my old leading edge exhaust caused a bigger rpm drop with carb heat applied than my Sutton does. Can’t really tell much difference in cabin heat.

  13. #53
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    I do not know the answer to Jim and Gordon's issues but with all the information I have gathered the one question I have is have you actually gotten carb ice and if you did would the system not melt it?
    The short answer is I do not know. I have been suspicious of carb ice a couple times but unable to get the carb temp above freezing. So there was no way of telling for sure if ice was present. That was before I came up with the technique I mentioned.


    Then the heat stops and the carb refreeze, now what?
    Low power (not necessarily idle) only lasts a few seconds (10 max?). I go back to cruise power as the carb temp starts decreasing. Then the cycle can resume, but most likely not. Also, just because the carb gets cold doesn't necessarily mean it ices up right away. This is a technique that is effective, based on measured carb temperature.

    One other matter I've encountered with the Sutton exhaust, that scared me pretty good the first time. The plane had been setting out in the rain and wind for a couple days, facing into the wind. I took off from my hayfield, and in climbout pulled carb heat as a precaution, because it's the still-cool engine that is most prone to carb ice. The engine quit immediately. It didn't cough or stumble, it quit. Over hostile terrain at fairly low altitude. I pushed the carb heat back in and the engine came right back at full power. I determined that water had blown in the nose bowl into the engine compartment, thence into the heat muff. It happened one more time in the same circumstances, but I was suspicious it might happen and I was ready. The lesson - do the carb heat part of the runup at high RPM and pull carb heat gradually, so that any water gets sucked up from the bottom of the muff gradually. Another solution might be a small drain hole in the bottom of the muff.

    Overall I like the Sutton exhaust and I'm not trying to bash it. But carb heat is indeed an issue. I think there might be a way to add baffle(s) between muffler and shroud to increase the carb air's contact with the hot muffler.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Thanks Jonnyo thanked for this post

  14. #54
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    I guess a STC should still comply with whatever regs the aircraft was originally certified under (like the CAR 3 carb heat temp rise above). Or if that's not the case how do they obtain and document any deviation for others to know? I have no opinion of Sutton's systems.

    I've suggested before adding a manifold pressure gauge as a quick indicator of an induction restriction...both on the air filter when flying in visible moisture or snow and in the carb. It does work if we pay attention to the instrument in level flight at constant power. The link in #47 supports that.

    Wrap an annealed door spring around the exhaust for more heat.

    Gary
    Last edited by BC12D-4-85; 02-10-2019 at 01:14 PM.
    Likes mike mcs repair liked this post

  15. #55
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    Thanks for your input Steve and taking the time to call Brian. If he claims one call, I will take credit for it. I will be polite and say it did not go well from my point of view.
    As to his points about the cold, wetter air going to the rear cylinders and drier to the front, two points. Would like to see the data on that and even if it is accurate, I do not understand his point. Please clarify.
    i do not know anything about carb ice detectors. I have a carb temp probe. I flew today. 20 degrees F ambient temp. Runup at 1700 was a feeble 20 rpm carb heat drop with an EI tach. An hour into my ride my carb temp was showing 64 degrees. Full carb heat for 5 full minutes did not change that temp one degree. Am I confident in this system being able to clear carb ice. Nope. My experience, Jim
    Likes TurboBeaver, mike mcs repair liked this post

  16. #56
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    points about the cold, wetter air going to the rear cylinders and drier to the front, two points. Would like to see the data on that and even if it is accurate, I do not understand his point. Please clarify.
    I agree. If Brian is on here perhaps he could clarify?
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Likes TurboBeaver liked this post

  17. #57
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    A quick search of what an “Elano” exhaust system is revealed that this style muffler has been used on various airplane types. The Cessna 152 muffler/system looks remarkably similar to the Sutton system with one exception. The shroud has 4 scat attachment points. I assume they take the carb heat feed off the muffler can with ram air. Cessna is dealing with an 0235, perhaps the heat is not adequate with the smaller displacement engine.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	856278D7-735A-477A-A308-AE7BF3E245A9.png 
Views:	46 
Size:	182.2 KB 
ID:	41438  

  18. #58
    Eddie Foy's Avatar
    Join Date
    Dec 2014
    Posts
    2,994
    Post Thanks / Like
    Surprisingly, he is not a member.


    Quote Originally Posted by Gordon Misch View Post
    I agree. If Brian is on here perhaps he could clarify?
    "Put out my hand and touched the face of God!"
    Thanks Bommer thanked for this post
    Likes cruiser liked this post

  19. #59
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Location
    Graham, TX
    Posts
    17,995
    Post Thanks / Like
    I remember hooking SJ's carb heat up backwards one time. He had great carb heat and poor cabin heat. Might be an interesting test to see what your carb temp gets to.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
    Likes cruiser, AkPA/18, mike mcs repair, Bommer liked this post

  20. #60

    Join Date
    Oct 2006
    Location
    Seldovia, Alaska
    Posts
    122
    Post Thanks / Like
    Quote Originally Posted by cruiser View Post
    I do not believe this is correct. The cabin heat is taken off the entire muffler under the can via Ram air. The carb heat is taken of the end of the muffler, outside of the can, and off a small portion of the left hand exhaust stacks under the small shroud. No ram air. This is a view of the carb air intake. Now if a guy was creative, and non certified, I suppose a Y tube could be used in the cabin heat duct to provide fully muffler can heated ram air to both cabin and carburetor heat.
    cruiser
    I was in error and you are absolutely correct. I was not aware of the baffle in between the cabin air vent and the carb air vent or that the carb air inlet is at the opposite end of the muffler If the Sutton is short of carb heat is likely because there is such a sort distance for the heat exchange to take place.

    I cant help but wonder what would happen if one ducted some of the ram air from the cabin heat to the carb heat. Carb heat is not in my experience ducted under pressure and I have no idea what that would do.
    Likes cruiser liked this post

  21. #61

    Join Date
    Jan 2007
    Posts
    1,498
    Post Thanks / Like

  22. #62
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    I checked my carb temperature rise a couple days ago. Normal cruise, 2400 RPM, carb temp 15 deg F. Pulled carb heat and max was 31 deg F. 16 deg rise. Both CAR-3 and Part 23 specify a 90 deg rise. I read them both yesterday and confirmed. How did this get STC'd?

    Personal opinion, but 90 deg seems like substantial overkill. However 16 deg is clearly insufficient.

    Edit, a little more data: Cruise altitude in this test was approx 1500 MSL. I did not check OAT, but probably mid to upper 30's. My carb air box is in good condition, rebuilt with excellence by Randy Rubbert, and it is properly adjusted. The scat tubing from muffler shroud to airbox is in good condition.
    Last edited by Gordon Misch; 02-15-2019 at 01:00 AM.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
    Likes mike mcs repair liked this post

  23. #63
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    Gordon how about another experiment? Connect a heater hose from the cabin heat shroud to the carb heat and see what it shows? Might tell the limits of that muffler's setup.

    So are you seeing a 15*F drop from ambient air in the carb venturi (~30 - 15*F)...cooling through fuel vaporization? Then I wonder if CAR3 and 23 measured the 90* rise over ambient air or carb temp?

    Gary

  24. #64
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Yeah, I wondered the same thing about the reference temp. It is ambiguous. If it's ambient though, then 90 would be even more dramatic, and harder to attain.

    And agreed, running cabin heat to the carb would establish a baseline. HOWEVER - do you really expect me to go without cabin heat when it's way down in the 30's outside?
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  25. #65
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    For science yes. Dress warmly and pretend you're Orville.

    Edit: Ok, then hook the carb heat up to the cabin inlet. Might get some comfort.

    Gary
    Likes Gordon Misch liked this post

  26. #66
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Haha, spoken like a Biologist!
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  27. #67
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    And as appreciated by an Engineer. Now go do the right thing for critical data and report back...Ha!

    Gary

  28. #68
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    Odd, to me, your carb temp readings are so wildly different from mine. 20 degrees ambient and 54 degrees on carb temp my last flight. Full carb heat at cruise power for 5 minutes resulted in no change. I have never seen below freezing temperatures on my carb temp gauge, Jim

  29. #69
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,463
    Post Thanks / Like
    Gordon, look in AC-23-8C. Flight test guide. The instructions for all testing is there. As I recall there is a condition when you add 100* to the calculations.
    N1PA
    Thanks Gordon Misch thanked for this post

  30. #70

    Join Date
    Oct 2006
    Location
    Seldovia, Alaska
    Posts
    122
    Post Thanks / Like
    I agree that it would be worth while knowing what the temperature rise in the carb would be with the cabin heat outlet hooked to the carb heat inlet. Keep in mind it is ram air your introducing. With ram hot air it will change your mixture significantly. Watch the CHT and RPMs during the experiment.

    I would be be very interested in hearing the results and I appreciate your doing the tests for the benefit of all of us.

    Stu

  31. #71
    BC12D-4-85's Avatar
    Join Date
    Feb 2016
    Location
    Fairbanks, AK.
    Posts
    1,188
    Post Thanks / Like
    Quote Originally Posted by cruiser View Post
    Odd, to me, your carb temp readings are so wildly different from mine. 20 degrees ambient and 54 degrees on carb temp my last flight. Full carb heat at cruise power for 5 minutes resulted in no change. I have never seen below freezing temperatures on my carb temp gauge, Jim
    I wonder Jim if it's possible your carb heat box is continuously leaking some hot air to the carb even when then flapper is closed? Maybe do a ground runup with the heater hose connected then removed to look for carb temps? You could do it in the air if careful to note any icing but...

    Gary
    Likes cruiser, mike mcs repair liked this post

  32. #72
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    I will give that a try. Of course, it has been my contention right from the start on this that my carb is not getting any, or much, hot air.

  33. #73
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Quote Originally Posted by cruiser View Post
    Odd, to me, your carb temp readings are so wildly different from mine. 20 degrees ambient and 54 degrees on carb temp my last flight. Full carb heat at cruise power for 5 minutes resulted in no change. I have never seen below freezing temperatures on my carb temp gauge, Jim
    Cruiser,
    Respectfully, I think there must be something amiss with your carb temp instrumentation. Possibilities might include, connected to a different probe somewhere, wires crossed, wrong connections at the instrument, incorrect location of probe? Dunno, just making wild guesses. However - it stands to reason that the venturi temperature cannot be higher than ambient. I doubt that there is anything wrong with your carb heat box, unless the carb heat control possibly doesn't actually activate the carb heat flapper. That seems crazily unlikely.

    But I can't imagine that something isn't wrong for venturi temp to indicate 30+ deg above ambient.

    No criticism intended, just thinking about the mechanics of it all.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  34. #74
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    9,808
    Post Thanks / Like
    Quote Originally Posted by Gordon Misch View Post
    Cruiser,
    Respectfully, I think there must be something amiss with your carb temp instrumentation. Possibilities might include, connected to a different probe somewhere, wires crossed, wrong connections at the instrument, incorrect location of probe? Dunno, just making wild guesses. However - it stands to reason that the venturi temperature cannot be higher than ambient. I doubt that there is anything wrong with your carb heat box, unless the carb heat control possibly doesn't actually activate the carb heat flapper. That seems crazily unlikely.

    But I can't imagine that something isn't wrong for venturi temp to indicate 30+ deg above ambient.

    No criticism intended, just thinking about the mechanics of it all.
    SIMPLE to check... before start OAT should be close to carb temp... providing not in hot sun or such...

  35. #75
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Quote Originally Posted by skywagon8a View Post
    Gordon, look in AC-23-8C. Flight test guide. The instructions for all testing is there. As I recall there is a condition when you add 100* to the calculations.
    Thanks, I did. I did not find any reference to induction icing other than a referral to FAR 23.1093, which reads the same, at least for "sea level engines" as CAR-3. That is 90 deg F rise at 75% power.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  36. #76
    cruiser's Avatar
    Join Date
    May 2002
    Location
    South Glens Falls, NY
    Posts
    1,410
    Post Thanks / Like
    Thanks Gordon, the temps I am referring to are when the engine is warmed up well and running. The reading is ambient temp prior to start. I believe I have read on here that the carb absorbs heat from the oil pan. I assumed that was the cause of the temps I an seeing

  37. #77
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,463
    Post Thanks / Like
    OK sorry, That Flight Test Guide is nowhere near as concise as the one for CAR 3. I'll have to see if I can find my old dog eared copy with some pages missing and hope that page is still there. This may take a little time. Every page is set up with step by step instructions with lines to place your data and the equations to make the calculations.
    N1PA
    Thanks Gordon Misch thanked for this post

  38. #78
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    Thanks - I'm in uncharted territory with those ACs, so I appreciate the guidance.
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

  39. #79
    skywagon8a's Avatar
    Join Date
    Mar 2008
    Location
    SE Mass
    Posts
    8,463
    Post Thanks / Like
    The CAR 3 guide came out prior to ACs. I can not find it on line. The following may give you some insight while I am looking in the attic.

    Carburetor Ice Test MethodologyEvaluation Final Report
    https://crcao.org/reports/recentstud...2015_12_21.pdf

    Also this is not what I'm looking for but is the procedure:
    From
    FLIGHT TEST GUIDE FOR ASSESSMENT OF AMATEUR-BUILT AIRCRAFT ACCEPTED UNDER AN ABAA3. Procedures
    All tests should be conducted in air free from visible moisture.
    The temperature sensing probe should be installed in the induction system downstream of the heater and upstream of the venturi. It may be necessary to make a tapping into the intake duct.
    Heat rise requirements should be met at an outside air temperature (OAT) of -10C at an altitude where the engine can develop 75 percent MCP. If it is not possible to obtain these conditions tests should be conducted at the required power setting at the lowest OAT achievable and reduced to the required condition.
    At the test altitude stabilise the aircraft in level flight at 75% MCP with the carburettor heat control in the cold position. Allow all parameters to stabilise then record pressure altitude, OAT, RPM, manifold pressure and carburettor inlet air temperature. Apply full carburettor heat and allow temperatures to stabilise before recording the new carburettor inlet air temperature. Repeat this procedure two or three times to ensure consistent results.
    Air temperatures should be measured with calibrated temperature probes. All other quantities may be recorded from the standard aircraft instruments.

    And this from Canada:
    https://www.tc.gc.ca/eng/civilaviati...-sub-e-291.htm
    525.1093 Induction System De-icing and Anti-icing Provisions

    N1PA

  40. #80
    Gordon Misch's Avatar
    Join Date
    Dec 2003
    Location
    Toledo, Wa (KTDO)
    Posts
    3,137
    Post Thanks / Like
    That is helpful, especially regarding OAT and location of temp probe. Thanks!
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)

Similar Threads

  1. Replies: 14
    Last Post: 12-15-2015, 04:23 PM
  2. Leading Edge Exhaust -- Exhaust Odor in Cabin on Final
    By Darrel Starr in forum Cafe Supercub
    Replies: 20
    Last Post: 06-01-2011, 10:02 PM
  3. need PA 12 exhaust advice
    By akpepperdog in forum Super Cub Sick Bay
    Replies: 1
    Last Post: 03-09-2005, 09:52 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •