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Thread: CHT, thoughts, tips, HELP....

  1. #21

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    Default Re: CHT, thoughts, tips, HELP....

    I don't know about running a carbed engine LOP - but do you have front cylinder baffles (like Gilbert's) front cyl baffles will warm the fronts and cool the backs

  2. #22
    Chris Iriarte's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    After reading this I took a look at my Tripe and lo and behold, it's missing this part, too. Is this perhaps part of the Brackett installation (which mine also has), to remove this part?

    I'm also missing the nose strut boot assembly mentioned in a parallel thread ... Interesting that it's in the nose strut AD for all Tri-pacers but the parts catalog still has it listed for only the later models.

    Chris

    Quote Originally Posted by vk6ad View Post
    I know this is a really old thread but it is the most relevant to my situation.

    My Tripacer has been flying for several years without the inlet scoop assembly (Piper part 13137) after a Brackett filter was installed. After reading these posts I want to have it refitted.

    The photo posted by "Rocket" on 02-21-2012 is excellent but it doesn't show how the scoop is fixed in position. There's nothing on the Piper blueprints to show how it should be fixed either. My original air filter had two mounting holes and there were nut plates on the two lower holes on the air box. There are cutouts on the inlet scoop that appear designed to clear the upper filter fixings if used but nothing that looks like screw holes.

    Can anyone help please?

    Phil, Australia

  3. #23
    Brian's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    Mark it seems odd to me that your Cyl Temps are over 400F yet your Oil Temp is running quite cool. These are Oil / Air cooled engines. When the cylinders are hot the oil should be hot as well. If my Cyl temps rise above 400, my oil temp will also rise above 200. Maybe more focus should be applied on your oil pump, oil pressure, oil temperature bulb accuracy, oil vernatherm if you have one, etc.

    When you put on the new cylinders did you remove or disturb the hydraulic lifter assemblies ? It seems like your not getting normal oil flow through your rocker covers for some reason and not benefiting from heat transfer from Cyl head to Oil.

    I'm also baffled by your ability to run a carbureted engine on the lean side of peak. Normally only fuel infected engines can transition ROP to LOP without unnerving rough engine operation. By the way Lycoming does not approve of LOP operation even on their IO engines for what that's worth.
    Brian
    Monrovia, CA

  4. #24
    Chris Iriarte's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    Sure they do ...

    http://www.gami.com/articles/bttfpart2.php

    Chris

    Quote Originally Posted by Brian View Post
    Mark it seems odd to me that your Cyl Temps are over 400F yet your Oil Temp is running quite cool. These are Oil / Air cooled engines. When the cylinders are hot the oil should be hot as well. If my Cyl temps rise above 400, my oil temp will also rise above 200. Maybe more focus should be applied on your oil pump, oil pressure, oil temperature bulb accuracy, oil vernatherm if you have one, etc.

    When you put on the new cylinders did you remove or disturb the hydraulic lifter assemblies ? It seems like your not getting normal oil flow through your rocker covers for some reason and not benefiting from heat transfer from Cyl head to Oil.

    I'm also baffled by your ability to run a carbureted engine on the lean side of peak. Normally only fuel infected engines can transition ROP to LOP without unnerving rough engine operation. By the way Lycoming does not approve of LOP operation even on their IO engines for what that's worth.

  5. #25
    Brian's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    Lycoming FAA Approved Service Instruction No. 1094D reads:

    "TEXTRON LYCOMING DOES NOT RECOMMEND OPERATING ON THE LEAN SIDE OF PEAK EGT. "

    Obviously LOP is routine on injected engines both continental and lycoming to save fuel.

    Regardless of this point I feel Mark may be looking too hard at air flow and baffling on solving his high Cyl temp issue, assuming his oil temp is actually only 170 when cyls are over 400. Mark consider checking your oil temp gauge calibration.
    Brian
    Monrovia, CA

  6. #26
    Chris Iriarte's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    OK, but there's a difference between "does not approve" and "does not recommend." Just wanted to make sure we weren't starting a "only satan worshippers run LOP" thread! =:-0

    Chris

    Quote Originally Posted by Brian View Post
    Lycoming FAA Approved Service Instruction No. 1094D reads:

    "TEXTRON LYCOMING DOES NOT RECOMMEND OPERATING ON THE LEAN SIDE OF PEAK EGT. "

    Obviously LOP is routine on injected engines both continental and lycoming to save fuel.

    Regardless of this point I feel Mark may be looking too hard at air flow and baffling on solving his high Cyl temp issue, assuming his oil temp is actually only 170 when cyls are over 400. Mark consider checking your oil temp gauge calibration.

  7. #27
    Mark Stevens's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    Thanks for the continued inputs and info...As for my oil temps, I have the typical Piper oil press and temp gauge, as well as an oil temp probe that feeds oil temp info to mi EDM 700 engine monitor. The piper gauge has it's pick up at the base our B&C oil filter adapter, and the JPI probe is out at the front of the engine. These two always read about 10 degrees different, but always in the 170 to 180 deg range.

    LOP OPS......for some compelling research on leaning techniques be sure to consider the vast amount of information in Savvy Aviator articles by Mike Busch. One very important piece of the LOP vs. ROP puzzle pointed out by Mike is that CHT is the best piece of information we have in the cockpit to indicate Internal Cylinder Pressure...ICP is CHT. These two values mirror each other.....and it turns out that if you measure the ICP at the most often recommended 50 deg ROP setting.....you would find your cylinders undergoing maximum internal pressure...or stress...without producing any significant increase in power, torque, or benefit to turning the prop or moving the aircraft. CHT & ICP BEGIN to decrease at 100 deg or more ROP, OR at 20 degrees or more LOP....THE ARTICLE I HAVE ATTACHED IS VERY INFORMATIVE, AND I OFFER A LINK FOR YOUR CONSIDERATION.

    http://www.avweb.com/news/savvyaviat...g198162-1.html

    i can run my O320 B2B LOP .... it takes adding in a slight amount of carb heat to turbulate the fuel air mixture to assist in equalizing distribution to all cylinders. This also seems to work best with partial throttle settings, as opposed to WOT at higher altitudes above 7500 feet where I am only able to see 20 to 21 inches MP at WOT . The trick seems to be getting all the cylinders to lean as close to the same rate as possible , so you don't end up with one cylinder becoming lean much earlier in the process compared to others, and producing the typical rough running engine.

    Mixture also contributes to the flame propagation and spread in the combustion cycle, and according to Mike, the recommended 50 to 75 deg ROP settings put the max ICP point ahead of the piston reaching Top Dead Center....so the piston is till coming up when the ICP reaches max value....and the piston has to be forced through this point by inertia, before starting to move the piston the direction we really want it to travel... LOP operations from 20 LOP and beyond... if able to do so, .shifts the max ICP point in the cycle to just after TDC, and beyond, where all of the combustion energy is then translated into moving the crank more efficiently.

    Again, I'm not trying to advocate anything other than basing decisions on efficient engine operation, with a primary goal of longevity, and ultimately safety, which may also yield economy in terms of fuel consumption.....on current modern research, not solely on the methods that may have been promoted by those that didn't have the tools or analysis that is now available to each of us that operate these engines.

    Any hints on increasing the differential in values between my high pressure upper baffled cowl and my lower low pressure cowl on a tri pacer with the original cowl, may help me the most.

    MARK

  8. #28

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    Default Re: CHT, thoughts, tips, HELP....

    Mark, I am amazed you can achieve LOP in your Pacer, good on ya. I was a BIG fan of LOP when I still had my C 205 with the IO 550 in it. I always ran LOP in cruise. I have not been able to achieve it in my Pacer. I am still concerned about my CHTs on climb out. When they get around 420 I level off or flatten my climb and pull the power back some. It is not long before the CHT gets under 400 then I can climb again. In cruise I run about 325 on all four cylinders. I guess the climb out temps will just have to be something I live with.

  9. #29
    Mark Stevens's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    Wayne, thanks for your comments and CHT TEMPS INFO. Of course your Pacer has a different cowl, and not all the places where high pressure air flow can be leaked to the low press side around the nose gear and the Sugar scoop on the bottom of tri pacer cowls....pacer cowls seem to work better....look better too in my opinion.

    Your experience in climb is alot like ours.....we take off at full power from sea level....climb at 85 mph to 500 ft agl then lower the pitch picture, increase airspeed to about 100 mph, and reduce MP to about 24-25 inches.....trying to keep our rear cylinders under 430.... In cruise like I was using yesterday at 4500 msl at 21 in mp, at 115 mph indicated with 100 deg ROP I saw 375 on front cylinders, and 405 to 410 on the rear...about the best I could do. I was checking out a new pilot in the plane and didn't want to demo LOP OPS on his first long flight in the plane. We averaged 9.2 gph start to shut down....over 5.0 hours flying. Oil temp on both gauges 170 to 185.

    I still think if I could figure out a way to direct some of the high pressure air from behind the oil cooler, or from some ducts cut into the baffle at the rear of the sugar scoop, and direct both of those high flow air streams out some augmenter tubes at the cowl exit so at least the cooling drag of that flow would hopefully generate a much greater pressure diff from the upper and lower cowl areas, it might draw more air past those rear cylinders??? And keep all CHTs closer to 380 or below.

    Any other tri pacers out there running engine monitors on all four cylinders seeing similar temps.....should we just be happy with the numbers we are getting??? Any other ideas on cooling those rear cylinders....???

    We have had both mags recently overhauled by Aircraft Magneto Service, Bainbridge Is, WA.....fantastic folks, would highly recommend them to all club members....they did my Colt mags too. New overhaul on carb, recent muffler, recent ECi Titan cylinders, new baffles, overhauled generator, brackett filter, we do have the cowl piece that mounts between air box and cowl and attempts to minimize air flow in that area....avail from univair...$150 for those that don't have one...we made new front baffles to cover and tighten up area around lower half of front cylinders....

    If I discover anything that improves our CHTs, I will certainly share....

    Mark

  10. #30
    Lownslow's Avatar
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    Default Re: CHT, thoughts, tips, HELP....

    If you have not re-checked your mag timing-to-engine, I would certainly do that. If, for some reason, your timing is advanced, you can run higher CHT's than normal. I've seen this on several engines. It seems that there are mechanics out there that sometime have difficulty making sure the timing marks are aligned perfectly when performing this procedure.

    Lou

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