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High oil temp

in General Tech Discussion 13 years ago
I am experiencing higher than normal oil temps (231 to 234 degrees) during cruise at 2500 msl using 5200 RPM with about 26 MAP. I fly a RV12 using a 912ULS engine. Outside air temps are between 90 and 100 degrees. To attempt to lower the oil temps, I have put a cerramic coating on the muffler (being very close to the oil cooler), added a vent plate at the bottom of the lower cowling. None of these modifications helped.

Do others out there using a Rotax 912ULS have higher than normal oil temps? Any suggestions?
Thank you. Steve

  • Re: High oil temp

    by » 13 years ago

    Hi Steven,

    What do you consider too hot? It's hard to pin point your problem if there is a problem without knowing a few of the following.
    First 235F or lower for this time of year is not high.
    Those can be very normal oil temps. If you have a prop pitch set and get less than 5500 rpm WOT you can increase temps quickly. If you see less than 5500 rpm WOT then take some pitch out to see 5550-5600. This will help unload the engine and help drop the temps. I have just been through this very thing with 2 other pilots and their temps went down 10-15F. Run around 5000-5200 cruise rpm as it runs a little cooler. The 912 runs a little hotter around 4500-4800. Let us know if this helps. The prop will make a big difference if it is set with too course a pitch. Some see up to 250F in oil temps this time of year and it can be an air flow issue, a prop pitch issue. You can if necessary drop the carb needle clip down to the 4th notch from the 3rd and run a little richer and that may help in some cooling.


    p.s.
    Don't forget to do a good carb sync

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

    Thank you said by: YEN NIEN YU
      
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  • Re: High oil temp

    by » 13 years ago

    Thank you Roger for the info. I have tested several different prop pitch settings but the greatest RPM at WOT was 5325 on T/O. With this prop pitch, I lost about 10 kts in indicated speed from my previous setting. With this flatter pitch, I did notice a few degrees lower in oil temp in cruise with 5200 RPM. Oil temp went from 232 to 229 in level cruise and fuel consumption went from 5.0 to 4.8 GPH. My main concern is the top of the green arch is 230 degrees and I'm well into the "yellow" range. If Rotax doesn't see running the engine above 230 degrees as something to be worried about, then why not raise the green arch to around 245 degrees. On tonights flight I hit 245 degrees in level flight (2000 msl) with 5200 RPM. Thanks, Steve
      
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  • Re: High oil temp

    by » 13 years ago

    Hi Steve,

    The yellow is just to get your attention and make you keep a watch on a possible real high temp. I don't know why Rotax starts the oil yellow at the lower temp. If the highest you ever see is 245F then I wouldn't worry especially since it is not there that long. If your prop pitch is set to 5500-5550 WOT flat and level then the usually take off rpm is approximately 4950-5050. That does vary depending on flaps and climb rate. If you get the pitch too flat then yes you will have great climb, but loose some of the cruise. Try the 5500-5575 and let me know. I bet you will like the balance between all the flight characteristics and fuel economy.

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

      
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  • Re: High oil temp

    by » 13 years ago

    Roger, I flew this morning and observed the following. During T/O the full throttle RPM begins at 5050 RPM. During climb to 2200MSL I see RPMs aroud 5300. During level flight with WOT, I get 5700 RPM. Do you think those numbers are close enough or more adjustments are needed.

    Today, I cruised at about 5000 RPM at 2200MSL for about 3 hours and the oil temps remained in the green at 228/230 degrees. My IAS of course was a few Kts lower, but in this warm weather in N.E. Texas I was pleased to see the oil temps remain in the green. Steve
      
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  • Re: High oil temp

    by » 13 years ago

    Hi Steve,

    The temps are good. You may want to reduce the higher rpm. Try adding 1.25 degrees back in to coarsen the pitch a little and try yo get the WOT rpm to 5500-5575. That will give you better all around performance. When the weather turns cold the WOT rpm will drop about 50-75 rpm with the more dense air which is fine.

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

      
    Report
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