Engineer Ted's How to Make Your Engine Last (while running)

Discussion in 'Maintenance Bay' started by Ted DuPuis, Jan 27, 2013.

  1. azure

    azure Final Approach

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    Reviving this thread because looking at the winds at altitude for my planned return trip from KMPV on Friday, it looks like an interesting situation. If I go at 8,000 or higher I will have a significant (at least 15 kt) headwind pretty much the whole way. If I go at 6,000, the forecast winds look practically neutral. But above 7,000, I feel completely comfortable running the engine WOT and aggressively leaned to the point where some cylinders are LOP, others 25-50 dF ROP (even with GAMIs, this is the best I can do without making it start to run rough). At 6,000, running WOT produces enough power (around 70% I think) that I'm not sure this is safe. I'm less concerned about detonation (which Ted has convinced me is pretty unlikely at less than 75% power in an IO-360) than about high ICPs shortening cylinder life. Am I worrying unnecessarily?

    Of course I can go at 6,000 and reduce power to 65%, but at the expense of a few knots -- maybe as much as 10. Since drag is greater at the lower altitude, my TAS is going to be a few knots less too (~5 or so) for a given power level. In that case, what altitude I choose may end up being a wash.

    I'd prefer to go at 6,000 WOT and aggressively leaned... IF it's safe to do so.
     
  2. tmyers

    tmyers En-Route

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    Do you have an engine monitor to keep track of CHTs?
     
  3. azure

    azure Final Approach

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    Yes -- I wouldn't be trying to run LOP without one.

    My CHTs are always well under 380, but when running aggressively leaned it's pretty clear that my #2 CHT goes down when running either richer or leaner, so at the "optimum" mixture it's near peak. I think that means that I'm running near peak ICP as well -- which is why I'm concerned and don't want to run that way at too high a power setting.
     
  4. timwinters

    timwinters Touchdown! Greaser! PoA Supporter

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    Not to hijack your thought but...

    Where do you find winds aloft forecasts for three days hence?
     
  5. azure

    azure Final Approach

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    On ADDS. Click on Winds/Temps and look at the graphical forecasts.
     
  6. timwinters

    timwinters Touchdown! Greaser! PoA Supporter

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    Thanks! I had missed that page...or forgotten about it.
     
  7. Jaybird180

    Jaybird180 Final Approach

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    Not sure I'm understanding where you say peak ICP is in the power curve.
     
  8. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    At 6,000 ft your ICPs will be higher just because you have more manifold pressure. Yes, it's safe. As far as shortening of engine longevity, it might reduce it by about 15 minutes worth.
     
  9. azure

    azure Final Approach

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    15 minutes worth? Ha! Okay thanks, that's reassuring. :)
     
  10. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    Remember, the life of the engine is a marathon, not a sprint. So it's additive wear over time from many factors. In most of our engines, sitting is the worst thing our engines see.
     
  11. azure

    azure Final Approach

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    Roger that. I know that many factors contribute to wear, I just don't have a feel for the magnitude of each factor. Obviously detonation is catastrophic and causes damage rather than wear, but I didn't know how much wear is caused by high ICPs alone.
     
  12. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    It's a sliding scale. A lot of folks in higher elevations get longer engine life - they never have high ICPs.

    Obviously I don't worry about it much since I usually pick the altitude that will get me there the fastest. Also keep in mind ICPs will be lower in summer due to higher OATs. But I'll fly at 25 squared LOP cruise in winter if that's the best altitude. It usually isn't, but I'll fly it when it is. And my engines do just fine on longevity.
     
  13. azure

    azure Final Approach

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    My understanding is that CHT and ICP are closely correlated -- someone (either Mike Busch or John Deakin, I forget which) says that CHT is a good proxy for ICP. I've taken this to mean that at a given power setting, at a given ambient temperature, higher CHT means higher ICP; not that you can necessarily rest easy if your CHTs are all within manufacturer's specified limits since other factors affect CHT besides ICP.
     
  14. gismo

    gismo Touchdown! Greaser!

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    In a given situation, CHT tracks ICP fairly well but as you pointed out there are many factors that alter that relationship (e.g. OAT, baffle condition, magneto timing, cowl flap position). Also CHT is such a slow moving indication that it's not a very practical tool for mixture setting.

    The relationship between mixture and the EGT delta from peak, OTOH is fairly consistent under varying conditions. Using fuel flow to determine % max HP and applying the following:

    <60% any mixture
    60-65% 0 to 10°F LOP
    65-70% 10-30°F LOP
    70-75% 30-50° LOP
    75-80% 50-70° LOP

    Those numbers make a good starting point but if you find this produces higher CHTs than you like just lean a bit further.

    The quickest way to find an appropriate LOP mixture setting is to lean the mixture until you see about a 5% drop in IAS. Another is to reduce the FF by 10% from what yields peak EGT on the richest cylinder.
     
  15. azure

    azure Final Approach

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    The first is pretty close to what I do. Leaning beyond peak EGT on the richest cylinder will make the engine run rough very quickly, because by then #3 isn't making much power. That's why I'm reluctant to run this way at higher power settings (70% and above), because I know that my cylinders are either straddling peak, or the richest cylinder (#2) is right at peak with the others LOP.

    Essentially I lean until rough and then enrichen until just barely smooth, watching EGTs and making sure that #1 and #2 are near peak or within about 0.2 gph ROP. Usually that produces about a 5 kt loss in IAS from peak power.
     
  16. Jaybird180

    Jaybird180 Final Approach

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    I am thinking that you would benefit from having the injector's flow balanced.
     
  17. azure

    azure Final Approach

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    They are well within spec, according to my mechanic. We went through all this last year when I first bought GAMIs. Something is going on, but I haven't had the time to track it down, and now I really don't have the time to do that.
     
  18. Jaybird180

    Jaybird180 Final Approach

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    From what I recall, they should peak within 0.5GPH from richest cylinder to leanest. That's the spec. If you can't even get LOP because #3 is too lean, then perhaps he goofed up the install (GAMI does specify each injector's location based one YOUR specific engine). Do you have an engine monitor?
     
  19. azure

    azure Final Approach

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    0.5 isn't the spec, it's GAMI's target when fine tuning their injectors for your aircraft. In most cases, they claim it's easy to achieve. In my case, it has proved nearly impossible. I can just touch 0.5 with a custom #4 nozzle (specially honed by GAMI) that's slightly richer than the one I have on there now. On paper, #4 is slightly leaner than #3 and it may actually be #4 that stops making power first. But in practice, it doesn't really help much, the window between #2 going LOP and the engine starting to run rough is not wide enough to be usable, and #4 already runs about 40 dF cooler than the others in the ROP regime. With the custom nozzle, it jumps to 80-100 dF and I'm concerned that it might mask an emerging engine problem if I had that diff reading on my everyday short hops where I wouldn't be running LOP anyway.

    By "spec" I meant the fuel flow distribution in the spider, with the nozzles removed.
     
    Last edited: Jul 6, 2014
  20. Jaybird180

    Jaybird180 Final Approach

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    Idk:dunno:

    What engine monitor are you using?
     
  21. azure

    azure Final Approach

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    EDM-700 without fuel flow or totalizer (I use the Cessna analog gauge for the GAMI lean test).
     
  22. MikeTuggle

    MikeTuggle Pre-Flight

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    OK... terrific thread.

    Now, a specific question: I am hoping to purchase a "straight-legged" Piper Saratoga (Lycoming IO-540). The POH is certainly the guide but...

    I had one pilot tell me go WOT and tune for 25" -- forget the books. And, "You should run it 50* ROP all the time, unless you want to end up way short of TBO guidelines." Another told me to run 50* LOP and just watch the CHT.

    Since this thread clearly indicates that engines may behave differently in different airframes, if you have a non-turbo Saratoga, how are you flying it?

    Thanks,
     
  23. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    50 ROP on that engine is the worst place to run it. Don't run it there. Follow the book for MP/RPM combos.

    Anyone who says 50 ROP is what you need to reach TBO is wrong.
     
  24. MikeTuggle

    MikeTuggle Pre-Flight

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    Thanks for the quick response, Ted.

    That one is at 1850 hours -- my hope was/is that it will make TBO. Last numbers were:72/80, 78/80, 75/80, 78/80, 73/80, 78/80. In the logs, one jug had to be pulled last year to remove "carbon under an exhaust valve seat...".

    I know that s**t happens, like it may have on one of the current threads, but even if it has been run ROP, if I were to get that one, I would plan to to use the 50* LOP setting. (It does have a JPI EDM-750.)
     
  25. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    So long as it's not making metal and legal compressions, keep running it.
     
  26. NoHeat

    NoHeat En-Route PoA Supporter

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    With the monitor, you can also watch the CHT, on climbout especially, to help the engine lifetime.
     
  27. Frugal Pilot

    Frugal Pilot Pre-Flight

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    My Cessna 150 preferred 5 quarts.
     
  28. Kiddo's Driver

    Kiddo's Driver Cleared for Takeoff

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    :confused:
    Did you reply to the wrong thread? Or did the thread start out talking about oil levels? The last page is nothing but leaning information. I'll go back & look.
    Found it! Posts 33-40 talk about oil level's (lack) of contribution to cooling and also mention that all engines have a level sweet spot.

    -Jim
     
    Last edited: Jun 7, 2016
  29. Jaybird180

    Jaybird180 Final Approach

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    His use of quotes would have saved you some time. But it's your time to kill.
     
  30. Checkout_my_Six

    Checkout_my_Six Final Approach

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    I think what missing here is MOney....and loads of it. :D

    ...cause we all know that's what keeps airplanes flying.
     
  31. BigBadLou

    BigBadLou En-Route

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    Let me add one thing that I learned helps with our piston engines (turbocharged, turbonormalized, supercharged or naturally aspirated).
    When you shut down, go pull the dipstick out a little to let the steam escape from the hot engine while you are parking your airplane.
    Your engine will thank you in the long run because you are removing moisture (steam) from the engine which means there will be less water in the crankcase after the engine has cooled down and water vapor condensed.
    How much does it help? I don't know the quantification. But every little bit helps.
     
    Kiddo's Driver likes this.
  32. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    I've heard some folks do that. It might help. It also then does leave a potential path for dirt and debris to get in the engine, plus you could always forget to put it back on before flight.

    Not saying not to do it, just saying that I don't and wouldn't go out of my way to add it. I think it would be more useful to add an engine dehydrator.
     
  33. BigBadLou

    BigBadLou En-Route

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    Good point, I failed to clarify that while I leave the dipstick open during my posti-flight, I logically replace it before I leave. I would not want debris or dirt in my engine either.
     
  34. Jaybird180

    Jaybird180 Final Approach

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    https://www.pilotshop.com/catalog/pdf/AA1000AviationConsumerArticle0001.pdf
     
  35. BigBadLou

    BigBadLou En-Route

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    Nice article, thank you.
    And see, in the good ol' days, they at least admitted "we do not have enough data to arrive at a conclusion" instead of pulling s**t out of their azz like the new NTSB kids do nowadays with their probable cause.

    But I have to wonder: why $235 for a simple drying system that consists of a $5 air pump, $5 box of desiccant, $0.99 timer and $0.50 of silicone hose? Does it include lifetime supply of fresh desiccant? :)
     
  36. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    When I was dealing with turbine engine failures at my last job (roller and ball bearings failing produces one hell of a mess, since they effectively turn the engine into a 30,000+ HP blender), not having a root cause was generally a frowned upon answer. Of course, those of us doing the work going in knew that we'd end up there. You can't take a million pieces of destroyed bearing and somehow reconstruct them to determine what failure mode existed, all you really end up doing is a design review of things that theoretically may have impacted the bearing in some way. You just had to hope that you caught a failure before it became catastrophic, THEN you could hopefully figure something out. On one program we were extraordinarily lucky in that regard - 4 bearings went bad in a few months, only one was catastrophic. We were actually able to figure out the root cause and a corrective action on those that was simple and easy to implement. Sometimes we made recommended changes that would make it more likely to catch a failure prior to it being catastrophic, but those were often unpopular since they typically involved more inspections.

    We always held the line and didn't make up BS, but it seems that nowadays people aren't as accepting of the fact that you have cases where you will never find out what happened. This is probably because we've gotten so good at investigations that it seems inconceivable that we could ever NOT know the answer.

    As to your question of why the price, I'd just make it myself. :)
     
  37. Mike the Comanche flyer

    Mike the Comanche flyer Filing Flight Plan

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    This is an old thread but I am new here. If I may reiterate what I was taught for comparison purposes.
    Never lean on initial take off/climb out in low density altitudes or reduce throttle. Keep the enrichment jets that only function at full throttle working. Reduce prop rpm to max. continuous if req'd but leave those full rich jets open. It cools the engine. I don't worry about being oversquare as Lycoming instructs for rpm reductions on my type but says nothing about reducing M.P. for this phase of flight.
    The reason your oil levels go down rather quickly at first, then stabilize is because the engine is designed for the throws of the crank to dip the oil pan and splash and spray the engine lower end. This atomizes the oil and is why your bellies are black. Loss stabilization occurs when the throws of the crank no longer have a deep enough tank to dip into. Splash and spray lubricate and cool .Oil loss is a design feature.
    Lastly, if you can, open the cowl after shut down to cool the accessory case.
     
  38. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    I don't believe that. The reason engine oil is not to be overserviced is precisely so that does not happen. If the crank were to dip into the oil it would not only reduce power, it would reduce oil cooling effectiveness.
     
  39. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    You don't know how to refresh desiccant?
     
  40. GlennAB1

    GlennAB1 Ejection Handle Pulled

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    The desiccant packs I see most frequently 80 Oz. Magnum Parks that state on them: Reactivation time in bag 12 hrs at 245° to 280°F.