Plane just out of shop – questions for the experianced

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    I just got the plane finished up and flew it home. For the most part everything was good.

    The crew said they did 3 test flight and ended up adjusting my MP between the left and right engine due to a 1.5-2″ split.

    However by the time I got home and put the plane back to 1,000 RPM after landing I had a 1.5-2″ split again. This also seemed to effect my fuel flow by about .8 gal.

    If I were to match MP on both engines then FF was about normal but rpm was about 500-800 difference between the two.

    Should I be concerned about this? Is this an easy fix and , why after 3 times around did this still end up off?

    Nothing like that in cruise that I saw.

    Second question: CHT – I have always read and understood that in cruise anything around 390 for CHT is not ok and to do something about it ASAP.

    Running Ram IV with AA Intercoolers I was at 10,000 and 54c outside running 31″ and 2400RPM. I pulled back to RAM specs of 21GPH and found my #6 CHT on my Left engine to clim up to 390. I then opened the cowl flow and not much difference so increased to 25GPH on that engine and got it down t 379.

    This is my first time seeing my engines because I just put in an insight G5 monitor and it’s great to know whats going on, but that high Temp concerns me.
    Saw the same on the right side as well and ended up running 25GPH on both to keep that hotest cylinder below 385. Is this an injector problem?



    At idle, there will likely be some MP split between engines due to slight differences in the fine pitch stops on the props. No problem. The problem is if there’s a difference at full throttle.

    You are now seeing your true engine cooling since you have an engine monitor. 380F or below is the optimal temperature. You don’t have GAMIjectors, right? They can help balance out CHTs since they make mixtures more even, but you should also check your baffling to make sure it’s fine. I’m guessing it was also a hot day out, which will impact CHTs. Try adjusting power settings as well to see what impact that has, and if you learn LOP that’s another good tool. First, though, I’d look at baffling.

    Don’t panic, this is what your engines have always done. 390 isn’t catastrophic, it’s just not ideal and will contribute negatively to engine life. Mid 400s, that’s bad.

    quote khouseholder1:

    However by the time I got home and put the plane back to 1,000 RPM after landing I had a 1.5-2″ split again. This also seemed to effect my fuel flow by about .8 gal.

    Kind of like my daughters. You can tell they are sisters – but very different in personality.

    I have chased the same thing only to surrender and accept it. Now I use that MP “split” as the “normal” and watch for a variation from that.

    Glad you have your plane back!



    Jim, the analogy with your daughters is very accurate to aircraft engines. The reality is that twins will pretty much always have some minor differences. So long as the important parts are the same (full takeoff MP/FF being the big one), the little differences can be ignored.


    Hey guys, thanks so much.. I have never seen a split at low RPM before today so that was why I asked.
    Yes at full throttle and cruise they are matched.

    I did validate baffle and they all look very good today.
    I am not running GAMI. I did pull back one engine with the new monitor in cruise and got back to 15GPH but couldn’t figure out how to get the gauge to LOP find. Reading the Manual now.

    It ran no problem at 15GPH at 31″ and 2350 but suspect I need to perform a lean test (Not sure how to do that) but I want badly to run LOP with the engines both to keep things cooler and get more duration.

    Coming from a Cirrus I’m very use to seeing LOP operations.

    I have to say I love the new Avionics and the AHARS driven into the AP400 makes an amazing flying machine. Flew the ILS down to mins last night and loved seeing the runway on the G600 the entire way.


    Oh – here is the new setup for those in the thread interested.



    [quote=”khouseholder1Running Ram IV with AA Intercoolers I was at 10,000 and 54c outside running 31″ and 2400RPM. I pulled back to RAM specs of 21GPH and found my #6 CHT on my Left engine to clim up to 390. I then opened the cowl flow and not much difference so increased to 25GPH on that engine and got it down t 379.[/quote]

    That’s a warm day. As Ted said that temps not an issue, what I’d be watching is what happens when you get above 15000. Also that a lot of fuel.

    That’s far warmer then I see at 340 at 10000, more what I see on a hot day above 20000.

    I’d think you will have address it.


      Nice looking panel. After flying behind a couple of Aspen panels for a few years, I would not want to go back to round gauges. There is just so much more utility now that didn’t even know to ask for before.



      I wish my 310R engines had only a 1.5-2 inch split. 🙂

      At idle they’re closer to 4-5 inch split. Of course, one is a dozen years old and the other is two. The newer engine has an even newer prop on it as well, of a different model too. (No more red oil in that one.)

      At cruise, they’re spot on identical. At pattern speeds and at equal MPs, one engine drops out of governing power before the other, so once that happens I fly by matching RPM. Not sure what sort of power they’re putting out but it’s obviously not much of a difference either way since I don’t feel much of a moment one way or the other.




      I would decowl and have someone apply the controls (mags off) on the ground and observe the motion of the controls on the engine fuel controller and prop. If everything was smooth with no bindings or catches, etc I am not so sure I would mess with it.

      To really set it up, both engines should follow SID 97, then the controls would be fine tuned. This would be hours and hours of work. The only thing I would verify is the mixture is not leaning out from idle to full power. Otherwise, I would leave it alone for now.



        Kelly, I think your post was off on the temp at 10K. 54dC is 130dF which I don’t think possible. I assume your fuel flow you quoted in the post was for climb power, and if it wasn’t, you won’t have much range at 10K altitude at those FFs. I would consider anything less then 28 GPH as too low of FF for climb; more like 30 GPH for your 335 HP engines. I run 28.5 on my 310 HP engines in climb.

        As to your MP spread at idle, I think you may have an intake leak somewhere or your idle FF adjustment is off. How is the idle cutoff check? You should get at least a 25 RPM drop and less then 60 RPM drop when you move the mixture to idle cutoff from full reach in a one second pull. As Eric said, conforming to TCM SB 97-3 is time consuming and costly so do the easy stuff first like soap checking the intake system for a leak and checking the idle mixture. If you have an intake leak on a turbocharged engine, it will not show up after the idle range as the turbo supplies lots of boost so it doesn’t care too much about a small leak; but a different story at idle.

        Without GAMI injectors, I doubt if you will be able to run much LOP unless you luck out with what TCM put in the engine for injectors. You just spent $210K plus so maybe another $1,600 is called for. And if by chance your injectors can get you within .5 GPH on the GAMI lean test, then my all means mark each injector so they always goes back in the same hole.

        The GAMI lean test is cruising around 6,500 feet, have a spare pilot aboard to watch out while you are doing the test as you will be heads down, set up a normal cruise FF (say 2300RPM and 30″ MP), then lean one engine slowly to about 19 GPH then carefully watch the #1 EGT for a peak number as you slowly lean further. Somewhere around 16 to 17 GPH the cylinder should peak and start down. You want to know the FF at peak and write it down. Go to full rich again and do the next cylinder the same way. The FFs should be .5 GPH or less spread for one engine. The other engine should have the same .5 GPH or less, but may be a different value. If the spread is more then .5 GPH, then your injectors are unbalanced and it will be hard to fly LOP in cruise.

        In cruise at FL190 and above, you should be able to run 40 degrees LOP and burn 15.6 to 15.2 GPH and get around 200 KTAS, but as you have a 414 you will probably be closer to 194 KTAS.

        Give it a try and let us know the results.


        Doug, I would look into a 5″ split at idle. That’s a lot. 1.5-2″, that’s more normal.


        Your right on the degress.

        Nice part about a logging engine monitor, it won’t let you lie 🙂 LOL.

        I was showing about 21.5-32 GPH on take off and when I pulled the right engine back I was back to 14.9 GPH when I was trying to test LOP. I can see the spread on the monitor logs pretty easy but the OAT was around 54 F instead of C.

        The only major split I saw as at taxi, looks like for the most part it was matched on climb.



        One other low cost idea for you.

        Note the coolest and hottest cylinders on each engine. Then swap the fuel injectors on those cylinders. This really fixed a similar problem I had and evened out all my CHTs and EGTs. It really made a significant difference.

        Checking and adjusting idle RPMs (not hard or expensive), doing an idle mixture check (should see a RPM rise of 25-50 RPM before dropping off, again not hard or expensive), and ensuring you have the correct full throttle takeoff fuel flow, solves most of the problems and you should see most of your cylinders within a tight range of CHT and EGT.



        Thanks Butch for the idea.. makes good sense to do that as I can see on the left side the spread is as follows.

        Let me know if I’m on the right track?

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