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  • Todd visits GAMI

    As I mentioned earlier I was scheduled to go down
    and visit with the folks that manufacture the
    GAMIjectors, have them installed on our 260SE and get the
    exact principals and operation recommendations straight
    from the guys that should know. The trip went well and
    their rep (Bill) spent about a half a day with me
    showing me the place and answering my many
    questions. I must say that before going down there I was not a
    great advocate of leaning lean of peak. It wasn't that
    I didn't think it would work or was necessarily
    unsafe (too many airplanes have been flown this way too
    long for problems not to show up if the fundamentals
    were unsound) it was more just an uncomfortable
    feeling about doing this and the chance of hurting a new
    engine. Over about a six part series I will try
    to relate exactly what the factory told me, my
    experience with the process and what I have decided to do
    with our airplane. Todd
    Kevin Moore
    Former 260se/stol Katmai with BRS owner; planeless for now
    sigpic

  • #2
    Part 1

    While I finish up the matching of fuel injector
    nozzles for a final flight, here are a few points that I
    learned during my visit with GAMI. The EGT is just
    a reference number so don't attach too much
    significance to it. The thing to watch closely is the CHT.
    Usually you will find one cylinder that is constantly
    hotter than the others. Watch it like a hawk. Temps
    higher than 400F are to be avoided (if possible) during
    the climb. At 410F-415F the cylinder barrels become
    somewhat oblong and the wear accelerates with the still
    round piston going up and down inside it. They really
    like to see around 380F to 385F in cruise. The big
    thing in all this is the CHT temp. With all things
    considered they feel that the cooler the temps the longer
    the engine life. Leaning during climb is to be
    accomplished to reduce engine roughness and to restore power
    only. They agree that the engine needs extra fuel to
    help cool things. You do not lean lean of peak (LOP)
    during the climb! Leaning LOP may be done (while
    cruising) at any power setting and at any altitude. If you
    wanted to you could be LOP at 3,000 feet pulling 80%
    power as long as the CHT's are in the normal range. LOP
    may also be done with a brand new engine during break
    in. You might richen the mixture very slightly during
    descent but very little. They recommended descent and
    landing with the mixture LOP. Bill cautioned me however
    everyone needs to remember than in case of a go around you
    must come in with the mixture first then the throttle.
    To do otherwise would not be good. By doing this the
    chances of shock cooling the engine are reduced and I
    must admit that coming down that way provides for
    amazingly constant CHT's during the descent and landing.
    Next time we'll discuss what equipment is helpful to
    have if you're going to go this route. Todd
    Kevin Moore
    Former 260se/stol Katmai with BRS owner; planeless for now
    sigpic

    Comment


    • #3
      Part 2

      The instrumentation you will need for this
      operation is a good engine analyzer. The Insight and JPI
      EDM700 are the preferred ones. The best is the latest
      JPI EDM700 with the lean find mode. It really takes
      all the work and risk out of the process. A
      good fuel flow computer like a Shadin or FS450 is also
      nice but not required. While matching the fuel
      injectors you are going to be looking for fuel flow
      differences of at most a half a gallon per hour and if
      possible .2 GPH. You can do it with the standard manifold
      pressure/fuel flow gauge but your going to really have to
      strain to see the differences. You will need to do this
      even after you get the GAMIjectors installed for a
      final check and possibly another adjustment. The idea
      is to get all the cylinders to peak within less than
      .5 GPH fuel flow. To operate LOP you do have
      to have the engine analyzer but suprisingly you may
      not need the GAMIjectors. The fuel flow spread on our
      factory stock injectors were fine to operate LOP at 22"
      and 2450 RPM. The spread became a little erratic at
      high power settings and even though the improvement
      would be minimal I elected to have them installed
      anyway. Bill said the injectors in our engine were
      amazingly close but it was an unusual case. The big thing
      to remember is that once you install the GAMIjectors
      you're not done yet. You still have to run the flow test
      and another final adjustment may have to be made. If
      so GAMI will send you out some additional exchange
      injectors to finish the job. To give you an example
      the fuel flow spread on our engine after the
      GAMIjectors were installed was .8 to .9 GPH. This is still
      more than the desired .5 spread that you need. I faxed
      back the results of the test flights and will install
      the replacement injectors and take it out for another
      test flight. With this spread I could operate LOP but
      there was a very slight engine roughness and a greater
      than normal loss of power. We'll see how the next test
      flight does with the replacement injectors. In
      the next part we'll take a look at the very strange
      world of LOP operations and how to run the mixture
      while flying. Todd
      Kevin Moore
      Former 260se/stol Katmai with BRS owner; planeless for now
      sigpic

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      • #4
        Part 3

        When operating in the strange world of LOP you
        have to have a good understanding of exactly what is
        happening and why. It is not the place to be just
        mechanically doing things without understanding the underlying
        fundamentals. Without getting to great detail and boring
        everyone to death here's some general information that may
        be helpful. When you order your GAMIjectors
        you will get a chart that lays out the power and EGT
        curve during the leaning process. As the mixture is
        leaned toward peak the EGT temps and HP will increase as
        you get to peak. After having passed peak EGT the
        temps and power will start to fall off. Now most pilots
        think that the engine will run rough on the lean side
        of peak. This is not the case as the engine will run
        very smoothly LOP if the injectors are closely
        matched. As a matter of fact I cannot tell any difference
        in vibration when on the rich or lean side of peak.
        Next you see that the further LOP you go the more
        power you lose. At a certain point the power loss
        really accelerates and in addtion to feeling the loss
        you see it in the reduction of your airspeed. The
        interesting thing though is that as you continue to lean LOP
        the EGT temps will start to come down along with the
        CHT. Bill said that as long as your CHT's are under
        400F and you are at least 20F LOP (on the last
        cylinder to peak) it is virtually impossible to have
        detonation. With all this in mind as you start to
        lean you will watch for the last cylinder to peak and
        that is the cylinder you then use for the reference.
        You want the last cylinder that peaks to be at least
        20F LOP. All the other cylinders will then be leaner
        yet. Obviously if you used the first cylinder that
        peaked the others (running richer yet) would be either
        at peak of just ready to peak. This is where the
        GAMIjectors come in. They keep the spread close otherwise by
        the time the last cylinder was 20F LOP the others
        might be so lean that the engine would be rough and
        lose a lot of power. There's also a common
        misconception that when the engine starts to run rough LOP that
        it is hurting the engine. This is not true. It
        simply shows that the cylinders are putting out a
        different level of power due to each cylinder having a
        slightly different mixture. It is not detonation nor will
        it hurt the engine. The only thing that will cause
        engine damage is a high CHT. Now after
        understanding all this you will understand that while flying
        LOP if the CHT's become too high to reduce them you
        will lean the engine further. This puts you further
        away from the peak EGT and will cool down the CHT's.
        If the CHT's are running a little cooler than needed
        to heat them up you will richen up the mixture. Just
        the opposite of what you do when operaing rich of
        peak. Bill states that running LOP produces
        less combustion byproducts which means it's better for
        the rings and valves, it's better for the cylinders
        due to the lower CHT's and if you have a leak in the
        muffler it will not produce carbon monoxide. Editor's note: ??? He also says that to run LOP the mag timing and the ignition system
        have to be in good shape. Next time we'll look
        at some of the actual numbers I have when LOP. Todd
        Kevin Moore
        Former 260se/stol Katmai with BRS owner; planeless for now
        sigpic

        Comment


        • #5
          Part 4

          After installing the first set of GAMIjectors I
          did a lean flight test and determined that the fuel
          flow spread from first peak to last peak was .9 GPH.
          After sending the information back to GAMI they then
          sent me four exchange nozzles. With these installed I
          did another lean flight test and found the spread had
          been reduced to .6 GPH. It turns out that cylinders 5
          and 6 have been brought in line with 3 and 4.
          Cylinders 1 and 2 are still out some and will need further
          adjustment. As I mentioned earlier you don't just stick a set
          of GAMIjectors in and forget about it. They
          sometimes require some follow up work. I just made a
          trip to Denver with our 260SE and here are some
          statistics and observations. With a power setting of around
          70% and altitudes of 5,500 ft and 6,500 ft the fuel
          consumption varied between a high of 10.2 GPH and a low of
          9.2 GPH. Pretty hard to believe but there it was. The
          CHT's were very good and ranged from the hottest at
          378F down to around 320F. My hottest cylinder is #1
          and I have worked to make sure the baffeling is as
          tight as possible. With all this done it is still the
          hottest and I am thinking that this may be due to the
          large oil cooler restricting the inlet air. To help out
          this situation I am adjusting the right cowl flap
          slightly to provide for a little more air through the
          right side. The EGT's are ranging from the high 1400's
          to the low 1500's. It is amazing that the
          engine can be run in this manner without hurting it. I
          do believe that it may be actually be better for the
          engine than rich of peak. I'm not a total convert but
          I'm getting closer. The engine ran very smooth LOP,
          the CHT's were lower than running ROP and everything
          worked very well. It does require a very close watch
          however as a very small change in mixture can have a
          large change in your temps. On this flight a change of
          .1 or .2 GPH will bring the CHT's to an unacceptably
          high level. Too rich the CHT's are too hot and too
          lean you're losing too much power and speed (still
          smooth though). It's a narrow band you're working in. As
          the spread of the injectors is narrowed it becomes
          better and it's very important to keep this spread to a
          minimum. Normally one tries to go high to get the engine leaned and
          here it really does not matter. As a matter of fact
          with our engine lower is a little better. When flying
          high at full throttle the spread becomes a little
          erratic and it's more difficult to run LOP. Some of you
          may have also noticed that when flying high the EGT
          spread becomes a little larger. The incentive to go high
          to improve fuel flow is really no longer necessary
          for our airplane. I would guess that optimum altitude
          for our 260SE is closer to 5,000 or 6,000 ft. Another
          thing I noticed is that there is little if any exhaust
          stain. Nothing residual to come out of the exhaust pipe.
          I also figured that by running LOP it cost me about
          6 kts in cruise speed. While I hated to lose the
          speed on my 3 hour trip it slowed me up about 18 miles
          worth. That's not too bad a trade off. Next time
          I'll have a final thought and be done with this
          subject. Todd
          Kevin Moore
          Former 260se/stol Katmai with BRS owner; planeless for now
          sigpic

          Comment


          • #6
            Part 5

            I'm finding that as we get the injector
            difference narrowed the speed loss is becoming less
            noticeable. This stands to reason as I'm not having some of
            the cylinders that peak first way lean (with the
            attendent loss of power) that I had when we started. I
            think that if I can get cylinders 1 and 2 with the rest
            the loss of power and airspeed is not going to be
            more than 3 to 4 kts. With our airplane I
            could not get the fuel burn down to where it's now at
            LOP even throttled back to 60%. In addition I am
            beginning to think that it really is better for the engine
            LOP. Jo and I are going to Cimmaron to pick up another
            260SE and I'll be running LOP down there. I'll let you
            know how it goes. Hopefully I will have the new
            injectors for a final flight later this week. It
            seems like a set of GAMIjectors run around $700. They
            also have a good web site you might want to look over
            www.gami.com. Todd
            Kevin Moore
            Former 260se/stol Katmai with BRS owner; planeless for now
            sigpic

            Comment


            • #7
              Part 6

              Well I received new injectors for cylinders 1 & 2
              and installed them. After having done another flight
              test it looks like the results are the same as before
              with a .6 GPH difference. I'll send the results back
              to GAMI but this may be as good as it's going to
              get. I just finished a flight to pick up a 260SE that
              just came out of the paint and interior shop and did a
              little flight test going down comparing LOP and ROP
              operation. At 23"/2450 rpm at 4,500 ft the fuel burn was
              10.3 gph with the EGT at 1548F with the hottest
              cylinder being 377F. In line with Kevins question about
              running at reduced power ROP I then tried that. By
              staying ROP and running at a reduced power level dialing
              in the same fuel flow resulted in about another 10
              kt speed loss (this is over and above the 5 kts
              speed loss by running LOP). I don't think this would be
              practical as the speed loss was just too much. I then
              reversed the proceedure and ran enough power to give me
              the same speed that I had LOP then went to 100F ROP
              and compared fuel flows. I found that I could
              maintain the LOP speed with a reduced power setting while
              burning 12.5 GPH. I keep finding that our engine 100F ROP
              produced too high a CHT so the 12.5 GPH figure represents
              the fuel flow required to produce a CHT of 384F while
              the EGT is showing 1441F. The reduced power setting
              that produced the same speed as the LOP setup was
              21"/2450 RPM (a power setting of about 60%). After
              all this flight testing here's the results as it
              applies to our 260SE (yours may be different). The choice
              is going 23"/2450 rpm LOP and getting about a 5 kt
              speed loss while reducing your fuel consumption down to
              around 10 GPH. The engine is smooth and the CHT's are
              cool. It does require a little more attention as the
              range you are working in is small. Too close to peak it
              gets too hot and too lean the power/speed loss is too
              great. The other choice is to fly the same speed as you
              do when LOP but do it at a reduced power setting
              which in this case is 21"/2450 RPM with a fuel flow of
              12.5 GPH. The engine temps are also quite good and the
              engine is very smooth (kind of loafing along). It does
              not require quite as much attention because all the
              other cylinders are running richer than the one that
              peaked and from a power/temp/speed stand point it
              doesn't make much difference. This also confirms what the
              GAMI folks are saying in that when LOP it takes about
              2" more manifold pressure to produce the same power.
              When flying trips that require maximum range I will
              certainly run LOP. Likewise while in a holding pattern,
              etc. running LOP makes a lot of sense. It also makes
              good sense to leave the mixture lean on descent to
              keep the CHT's up. I have not made up my mind as to
              wether or not I will run LOP on my cross countries.
              While I really like the LOP operation I also like
              running the engine at a lower power setting and the 2.5
              GPH difference doesn't really matter that much to me
              (unless I need the range). It's a tough choice but it's
              nice to have options. Running LOP is another tool that
              in some cases will be mighty helpful. And speaking
              of helpful the crew at GAMI is great. They have gone
              out of there way to help me and I am most grateful.
              Todd
              Kevin Moore
              Former 260se/stol Katmai with BRS owner; planeless for now
              sigpic

              Comment


              • #8
                Addendum

                As you may remember I ended up with
                a fuel flow spread on the GAMIjectors of .6 GPH and
                thought that might end up being good enough. Well I was
                wrong and the GAMI guys aren't giving up. They are
                sending me four more injectors to try out. They just
                don't give up. This will mean that after having the six
                GAMIjectors installed at the factory they will have sent me
                ten more injectors to finalize the installation. As I
                said you sometimes just don't install a set of
                GAMIjectors and forget it (although I think our engine has
                been exceptionally difficult). It's also obvious that
                GAMI really goes the extra mile for their customers. I
                like that. Todd
                Kevin Moore
                Former 260se/stol Katmai with BRS owner; planeless for now
                sigpic

                Comment


                • #9
                  GAMI update

                  The folks at GAMI sent me another two injectors
                  to finish balancing out our injector set. After the
                  intial installation of the full set of GAMIjectors these
                  last two injectors put the total follow up replacement
                  nozzles at eight. These last two injectors for cylinders
                  5 & 6 seem to do the trick. After having done yet
                  another fuel flow test the total fuel flow spread is now
                  down to .4 GPH. The performance difference is
                  noticeable as there is not the power loss ie speed loss that
                  there was before. The fuel flow is a little higher as I
                  don't have to continue leaning as much until all have
                  peaked. I could bring the mixture back a little more but
                  then the power really starts to drop off. It looks
                  like now the fuel flow at 23" and 2450 rpm @ 5,500 ft
                  will run around 10.9 gph (it had been around 10.2 gph)
                  with a speed loss of around 3 or 4 kts. While
                  I am quite sure that most engines do not require
                  the follow up work ours did it points out that simply
                  putting the GAMIjectors in and not checking them is
                  probably not the best way to go if you're going to operate
                  LOP. It also shows how dedicated the staff at GAMI is
                  when it comes to follow up work. Todd
                  Kevin Moore
                  Former 260se/stol Katmai with BRS owner; planeless for now
                  sigpic

                  Comment


                  • #10
                    GAMI on mixture settings during descent

                    After having been to the GAMI factory I have been
                    watching the rate of cooling on descent very closely. In
                    the old days you throttled back to descend and as you
                    went down richened up the mixture. As the GAMI guys
                    told me it works much better to throttle back and
                    leave the mixture lean. When throttling back you
                    actually want to see the EGT's start to come up a little.
                    During a rapid descent with reduced power I am now
                    actually leaning the engine out and using the higher EGT's
                    to keep the engine from cooling too fast. The lower
                    power settings (20" or below) make it virtually
                    impossible to hurt to engine by over leaning and it is truly
                    amazing how well you can stabilize the CHT's during a
                    rapid descent by increasing the EGT's. GAMI also
                    encourages their customers to leave the mixture aggresively
                    leaned during the approach and landing. Just remember to
                    run the mixture in before applying power on a go
                    around. On a go around they want you to get used to
                    applying power from the right to the left. Run mixture in,
                    prop in then the throttle. Todd
                    Kevin Moore
                    Former 260se/stol Katmai with BRS owner; planeless for now
                    sigpic

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