fbpx

 

Hello All
I am trying to find out what the ideal MP would be at high cruise in the KF Vixen with a 912UL. Presently I run at 28+inches at 5/5300 RPM. I set the IFA prop for 5500+ in level flight, then add a hair more pitch and pull the throttle back an inch or so to give me 5000+RPM.
Everything runs smoothly,no heat issues, plug color is right on.
I cannot get MP much pressures lower unless I run at well under 5000.
Are there any issues with operating this way?? Does MP mean very much on a 912?? Comments and experience requested.
Cheers
Don
  • Re: MANIFOLD PRESSURE

    by » 12 years ago


    Hi Guys
    I am a bit surprised that no-one wants to comment on the MP issue. Are these readings what most folks are getting? Are high (+28 inches MP) what these engines normally cruise at? Thanks.
    Cheers
    Don

  • Re: MANIFOLD PRESSURE

    by » 12 years ago


    Hi Don,

    I'll jump in here. To start some like to use the MP more than others, but on a 912 it's not that important compared to the 914 turbo. Some pilots like to use the MP to help get set up with an in flight adjustable prop and fine tune things. The MP is usually 1-1.5 in. lower than ambient. The pilots I know care more about rpm. We just had this discussion on another forum. If your prop pitch selector has let's say 7 positions. You will usually set it for 5800 rpm WOT for take off and don't care about the MP. When in cruise some have personal preferences they like to fly at and it is usually rpm dependent. As an example; some will set the cruise prop pitch to get 5500 rpm WOT and fly there the whole time. Some will set the pitch to get 5700-5800 rpm WOT and then throttle back to 5200-5500 rpm. It just depends on what the pilot wants. Doing it this the MP isn't that important. If you really like to use the MP and make fine tune adjustments then by all means have at it. Is either really wrong, no just different and personal preference. To really be good at using the MP a
    pre-printed chart would be helpful if looking to get a certain performance percentage from the engine and even that would be changing.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


    Thank you said by: Don Hudgeon

  • Re: MANIFOLD PRESSURE

    by » 12 years ago


    G`morning Roger
    Thanks for the informative reply. It is pretty much as I suspected. Your comment about MP`s on a 912 being about 1.5 inches less than ambient are what I get. Of course if I reduce RPMs substancialy then the MP reduces as well.
    I`ll just continue happily running as is.
    Thanks again
    Don

  • Re: MANIFOLD PRESSURE

    by » 12 years ago


    Hi Don,
    I usually set cruise at 5100 rpm and 25.5 "HG Map with the inflight adjustable prop , this gives a good cruise speed and still gives some throttle input left to get to the 5400rpm range WOT level (3500'ASL). all my temps are even and good at this setting.

    I have noticed different numbers with altitude, on the rare occasion I get up to 7500'ASL I saw a lower MAP of 23.8"HG with all the other numbers the same.

    I primarily use the rpm and the egt's to set the prop, too fine of a setting makes the front two egt's temps rise, too coarse and the rear egt's temps start to go up .

    This data is what I have found with my setup/ 912ULS , Ivo medium IFA, Dynon D120 EMS , 2 cht senders, 4 egt senders, and dynon Map sender.

  • Re: MANIFOLD PRESSURE

    by » 12 years ago


    On my custom 912UL turbo, efi and intercooler I get 43" 5800rpms on take-off. Climbout on the CS propeller is set to 5500rpms and approx 38" MP. Cruise settings from sealevel up to 10.000ft I run 5000rpms and anywhere from 28-34" MP continuous. I burn 16-18l/h at that setting witch should give me in the range of 100-110HP in cruise with the intercooler really cooling down the intake airtemp.

    No problems with the temps. 150KTS IAS, 70-80c CHT / Coolant and 90-100c oiltemp. Included is a screenshot of my EFIS - Sonex.

    Thomas - Norway


You do not have permissions to reply to this topic.