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Hi guys the new forum looks like it maybe very useful,

Something I am not to sure about.....I have a 503 dcdi with about 20hrs on the clock...yes its new out of the box,

Anyway its seems to run cool CHT wise, with both cylinders at around 150c/300f, the book fig is 180c/360f to 220c/430f,

What do you think and what does yours run at,

The 503 is on a trike and at cruise the RPM is aprox 4900/5000,

The EGTs are ok at aprox 600c/1115f...although I did raise the needles one notch from factory settings when I fitted the motor as the EGT was at max...but it was a cold time of year +4c/40f, but as the OAT is higher now it maybe worth dropping them back down,

Its bothers me that with it being a bit on the cool side it may make the motor tight and more prone to seizing....What do you think guys.

Nick.
  • Re: Rotax 503 CHT to cool.

    by » 10 years ago


    I would go by the book on the needle position, my 503 DCDI CHT is 300ºF and my cruse RPM is around 5 000 to 5,200. Your EGT´s were probably at max because of improper propeller loading. It is highly improbable that your engine would seize at thees CHT temps, one important thing to do is a proper worming of the engine before gong on full power. the most common thing that most pilots blame on high/low EGT´s and high/low CHT´s are the carburetors, they start tuning them for them to see the numbers they want, I would go by the book on the tuning and see if I have proper propeller loading. There is an article on this topic from a well known pilot, I will try to find it and post the link for you.
    Fly Safe.

  • Re: Rotax 503 CHT to cool.

    by » 10 years ago


    I could not find the article I wanted to show you but I found this http://www.askbob.aero/node/240 Hope this helps.
    Fly Safe.

  • Re: Rotax 503 CHT to cool.

    by » 10 years ago


    Hi D/S I will have a read of that later, re loading my prop I have pitched it for 6500rpm on climb out which everybody tells me is right,

    I did experiment with more pitch but it made little or no difference to my CHT...I think the EGTs came down just a bit though....I have since re-set it for 6500rpm max,

    Re warming the engine before full power....I normally warm the motor for 10mins before taking off...but my CHT will prob be around 125c/260f.

    How long would you recommend warming up and to what CHT before take-off.

    Nick.

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