fbpx
Login

 

Jump to Forum..

engine stumble at WOT

in 912 / 914 Technical Questions 7 years ago

  • Re: engine stumble at WOT

    by » 7 years ago

    I didn't pump a full gallon out of the carbs, but I will do tomorrow.

    the blueish line is altitude on that chart.

    I agree with you on the pitch of the prop having read the service letter rotax put out 12/2016 on 5200 or more at climbout. I did flatten that pitch and am seeing 5300 now which maybe too flat but I would prefer climb performance at this stage than cruise speed. I measured my gaps to 0.027

    That's interesting on the spark at WOT... what is the best way to test an individual spark lead and plug ?



    air filter is clear and brand new.

    I will take the spark plugs off again and check them all and report back.
      
    Report

  • Re: engine stumble at WOT

    by » 7 years ago

    I was finally able to make out the audio in the video wearing a headset.
    Correct me if I am wrong.
    I hear the engine Surging with an occasional miss.
    I do NOT hear a Spark misfire, normally accompanied by the fuel igniting in the tailpipe with a loud Bang.

    This sound like a Lean fuel mixture on one side.

    Carb Sync/Balance is a measure of the Air flow through the carbs.
    Fuel mixture issues will have no effect on the Carb Air Flow Sync/Balance.

    It still looks like a fuel issue.

    Pump a gallon++ from EACH fuel line taken directly off of EACH Carb.
    Ideally, take off both lines and point both into a container at the same time.
    Do they both deliver the same flow or is one side better than the other?
    Remember the flow rate matters. expect a gallon in ~2 minutes, No more than 3. Time it!
    3-5 gallons would be even better to confirm the tank vents are working.
    Were the vents confirmed?

    Recheck the Carb fuel input fittings for debris.
    You may have cleaned the carbs only to reintroduce debris if you did not flush the fuel lines while they were off.

    What is the history of the gasoline?
    Are the tanks filled from 5-gallon cans with auto gas?
    Are the cans fully pressure sealed during transportation? No open vents!

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: engine stumble at WOT

    by » 7 years ago

    ok this morning I tested the fuel flow by disconnecting the banjo bolt connection at the left carb. I ran it for 5 mins and got 5l of fuel which is 1.3 gallons. The return is still running at this time. This is only coming from one carb, the other feed is connected to the right carb.

    I need to check (my notes aren't with me) but I believe that at the mechanical pump inlet I performed a volume test and saw 1 gallon in about 120 secs.
      
    Report

  • Re: engine stumble at WOT

    by » 7 years ago

    on gas - when I got the issues in a couple of flights I emptied my tanks and filled with 100LL to eliminate fuel quality or maybe vaporization as an issue. the 100LL was direct fed into fuel tank by the fuel truck.

    I did check my tank vents and they are working.

    I checked the color of the plugs and they are white/slightly off white and the plugs look to be in good condition.

    I checked my spark cables as well, I could feel a good mechanical connection to the plugs and confirmed the cables weren't strained and were connected solidly to the ignition units.

    Really appreciate your time on this Bill, this is really helpful
      
    Report

  • Re: engine stumble at WOT

    by » 7 years ago

    I just did some testing on my fuels lines and ran fuel for 5 mins at each point

    Before mechanical fuel pump
    28 gph displayed on gauge
    I filled 2.4 gallons in 5 mins

    Outlet of mech pump (21.4 gph displayed on gauge)
    I filled 1.75gallons in 5mins

    Left carb at union
    (15.8 on gph displayed on gauge)
    I filled 1.25 gallons in 5 mins

    (I can confirm my fuel cube is accurate !)

    I also check my spark plugs, all slightly off white

    I check the integrity of my spark plug leads and connectors alll good.

    I scoped down the fuel filler neck and I see a good spray on the return line.

    I also checked that I got no difference between running for 5 mins with hose off at mechanical pump and fuel cap on and off and there is no difference
      
    Report
You do not have permissions to reply to this topic.
Related Topics
Title Category Replies
912 UL Stumbles at full power. General Tech Discussion 3
Engine will not make power after carb install, post-overhaul General Tech Discussion 36
Fuel System Pressure Testing before engine start General Tech Discussion 1
Service Bulletin: Inspection and maintenance after an overload clutch slipping event on ROTAX® 915 i and 916 i (Series) Aircraft Engines 915iS Technical Questions 6
Whining Engine Noise at Takeoff 915iS Technical Questions 7
Follow Us

Recent Videos

Safety First!

 

To receive critical-to-safety information on your ROTAX Engine, please subscribe to
ROTAX-OWNER.COM

ROTALK News



ROTALK NEWS Episode 5
Rotax-powered Sling aircraft from The Aircraft Factory, the AVMAP Navigation and engine monitoring system, and the Rotax powered Tucano Experimental and Light-Sport Aircraft.



ROTALK NEWS Episode 4
ROTAX's 915iS-powered Aquila A211 test aircraft, the Scheibe SF-25C Falke (first-ever 912-equipped aircraft!) and ROTAX factory in Gunskirchen, Austria.


ROTALK NEWS Episode 3
Michael Smith's Rotax-Powered Searey Circumnavigation, the amazing Rotax-Powered Lockwood Aircam and Anthony Caere's chimpanzee rescue operations.

Prize Giveaway!


SUBSCRIBE NOW
to automatically enter this years draw!

Login