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High EGT

Category: 912 / 914 Technical Questions one month ago

Hello forum, here my question.

I use a 912ULS in my MCR4S, at 600 hr the carbs are overhauled by a mainenance company. After overhaul my engine is running much hotter in high power settings  (5000 rpm 26").  EGT is over 800 dgrC where it was 50 dgrC lower.  I put the needles higher but this changed nothing. The guy who did the overhaul told me to bent the bowl lever to have a higher petrol level in the float bowl. Is this the right solution to let the engine run richer in higher power settings?

 thanks upfront, Hans PH-SKY

  • Re: High EGT

    by » one month ago


    What about other parameters?

    Like Oil Temp?

    Coolant temp?

    Spark plugs conditions?

     


  • Re: High EGT

    by » one month ago


    Oil temp and CHT temp also running about 5-10 dgrC higher.  plugs look good.


  • Re: High EGT

    by » one month ago


    800c (1472F) is well within the niormal parameters, but average seems to be around 1350F to about 1425F. This can vary depending on each person's engine configuration. Raising the needles a notch should have lowered the EGT a bit. (around 80F+/-). Tweaking the float armature shouldn't have affected the EGT. That controls the fuel level in the bowl, but not the burn in the cylinder. The needle and jet control the fuel flow and your needle raise should have made some difference and made it a tad richer. What notch was the clip in before you moved it? The brass float armature should be 10.5mm from the edge of the carb to the top of the brass armature when the carb is upside down. This should have been checked during the overhaul.

    The only real way to rule out carb internal issues is to have someone take them back apart and check things. They may have done something wrong, but there would be no way of knowing without a look see. Since this work was done before the higher EGT's it stands to good reason this work may be the cause and the first place I would look. I know this isn't what you want to hear, but seems to be the most likely cause. I would have someone else other than that same comapny take a look. I different pair of eyes.

     


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell

  • Re: High EGT

    by » one month ago


    First of all cylinder head temp is more important than EGT. EGT IS USUALLY HAS MEANING IN TURBINE ENIGINES

    Read an article that really explaineS  what EGT MEANS

    EGT MYTHS DEBUNKED SAVVYANALYSIS.COM BY MIKE BUSCH. 

    EGT MEASURES GASES AFTER PISTON POWER. IF YOU HAVE UNBURNED FUEL IN GAS IT'S GOING TO READ HIGH. EGT IS A VERY INACURATE MEASURE OF ENGINE STRESS. CHT IS INDICATOR OF ENGINE STRESS. WINTER FLYING COMPARED TO HOT WEATHER FLYING ALSO WILL EFFECT WHY.

    READ ARTICLE SEVERAL TIMES IT HAS GOOD INFORMATION RELATING TO FOUR CYCLE ENGIN.

     

     

     

     

     

     

     


  • Re: High EGT

    by » one month ago


    EGT'S and CHT's are two different things. You can certainly use them in combination with other readings and together. EGT's are more important and read almost instantly and much faster than a CHT and the EGT give an indication on how the cylinder burning is going. It gives clues to leanness and richness to carb, fuel issues and even eletrical issues for firing of the plugs. The CHT is a water cooled system for the heads and reads much slower and doesn't really give you a true indication of the burn inside the cylinder. CHT is just too slow to respond for immediate help with an in flight problem. The CHT's are affected by the air flow through the radiator and other components on the engine setup. The water cooling can mask what's going on inside up to a point. Depending on the engine configuration a CHT may not indicate trouble inside a cylinder until it's too late. Also fuel is part of the internal cooling within the cylinder. Too little fuel is lean and cause damage and too rich USUALLY just causes poor running, but cooler EGT and CHT temps.

    We can use all readings to help diagnose an engine's performance, but they should be used together with an understanding of how one affects the other and what they are telling us.


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell

    Thank you said by: Crew Feighery

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