Dear,

On my pusher config aircraft I'm having problem with high CHT temps that keep on rising during flight until 140 deg C. I'm using waterless NPG Plus coolant.
What I'm doing is to install two Rotax 12-fins radiators in series side by side so that coolant gets more time passing through the coolant radiator and gets cooled on 2-stages. Is it safe to be done or would I face any unintended consequences? Did anyone do it before?
  • Re: High CHTs - Dual Radiator in Series ?

    by » 6 months ago


    "I'm using waterless NPG Plus coolant."

    You shouldn't be using this plus it carries a 20-30F heat penalty. Dump it and use a Dex Cool 50/50 mix.
    Water absorbs and releases heat far better than waterless. Waterless isn't recommended anymore. You'll be happy you did.

    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 CHTs - Dual Radiator in Series ?

    by » 5 months ago


    CHT Depends on location of radiator and fresh air throw on these radiator can be cool it.
    The duct that provides fresh cool air can be redesign for keeping the CHT on lower side.
    The value of airflow mentioned in operator manual book.

  • Re: High CHTs - Dual Radiator in Series ?

    by » one month ago


    The 50/50 Dexcool should do the job.  But, I’ve also discovered a second defense, if and when engine temperatures start soaring (or the red warning light has already started flashing): managing the hottest-EGT reading via the EIS. First, I reduce AOA (if climbing) and throttle back, until I find the “sweet spot,” where hottest-EGT drops rapidly (i.e., 5-8 seconds) by at least 25-50 F degrees (or more). I move the throttle around (usually down, but sometimes up) and select the RPM that gives me the greatest drop in the hottest-EGT! Usually, this “sweet spot” exists around 4,800- 4,950 rpm. I hold it there and I soon see engine oil temperature and CHTs dropping dramatically too, in response to “less work” (thus less heat) the engine is doing. And if throttling down does not yield a sweet spot, I always remember to try going up. I’ve found the hottest-EGT sweet spot to be a very effective way to help manage high engine temperatures in hot weather. Just my 2 cents...


You do not have permissions to reply to this topic.