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I am experiencing on all the 914 installed on my airplane and some friends, a strong drop in MAP starting at 10.000 feet (max MAP 35) until a dramatic drop at 15.000 with a poor 30.5. From the 914 user manual, until 15.000 I should have full continuous power, that is at 35 MAP. But with the throttle at WOT, i cannot see more than 35 at 10.000 dropping until 30 at 15.000.

Someone else is experiencing the same situation?

  • Re: 914 MAP drop at 15.000

    by » one month ago


    Hi Alfredo

    Max boost is 40 inch at sea level pressure.  Max continuous is only 33/35 inch.  Max continuous is not WOT, it is at 5000. (full throttle on the TPS is for 5800 RPM and will open the enrichment system giving you a rich mixture for take-off)  If you have a constant speed propeller set your load to get 5000 RPM and then look at your MAP.  You must pull the cable back to the 100 % power position first.  To test this switch off the TCU momentarily while in flight and then switch back on to reset the TCU.  Be sure that you have done the preliminary idle to max throttle settings for the TCU.  

    If this is not an issue consider you may have a sticky wastegate or slight leak in the pressure side of the intake.  Remember that these numbers work only at the standard pressure and temperature conditions. 

    Cheers


  • Re: 914 MAP drop at 15.000

    by » one month ago


    forgot to include  relevant pages from installation manual for reference.  

    Use the new BUDS software and connect with a serial to USB adaptor to run the BUDS 4.0 software to set throttle position and find the 100/104 % position for your throttle leaver or cable reference.

    Cheers

    38632_2_iM throttle 914 .jpg (You do not have access to download this file.)
    38632_2_IM throttle pos 2.jpg (You do not have access to download this file.)

  • Re: 914 MAP drop at 15.000

    by » one month ago


    I will talk to my mech and I will keep you informed. 

    What I saw in the last flight at 15.000 ft, is that if I reduce the RPM from 5500 to lower rev, the MAP decrease. Always at WOT. Next flight I will keep the RPM at 5000 rpm and I will note the MAP. Always at wot? or at 100% throttle?


  • Re: 914 MAP drop at 15.000

    by » one month ago


    Please refer to the installation manual and the maintenance manual heavy.  WOT will open the port to give you takeoff mixture (rich) above the 100 to 104% throttle position on the throttle position sensor. (TPS)  The value for cruise is between 100 and 104% of TPS setting and load the engine to 5000 RPM with pitch for constant speed propeller settings.  If you are wide open throttle you will run rich.  While you can run 5500 RPM remember that the numbers shown were never given for fixed pitch and the exact numbers will never line up.  With a fixed pitch your loading will be very light at altitude and normally you have to throttle back to control RPM.  The fixed pitch is losing air density and the engine with a turbo is trying to maintain pressure.  The change of load is about 3% per 1000 ft of altitude as a general rule of thumb.  So at 10,000 you are down 30% on prop load.  

    If in your setup 5500 is seen when you are at or below 104% of TPS then you are OK for flight but I am sure it will not match the MAP from the operator's manual chart. 

    I agree you need to test it at 5000 RPM with 100% TPS.  I am just making a guess but it sounds like you are using a fixed pitch and this is always going to skew the numbers from what they show.  

    Cheers


  • Re: 914 MAP drop at 15.000

    by » one month ago


    Sorry. I forgot to write that I use a variable pitch. 

    I will try with 100% throttle and report the result

     

    thanks to everybody 


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