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Thread: Low oil temps and high CHT temps..

  1. #1
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    Default Low oil temps and high CHT temps..

    I have about 60 hours on my EX-2 now. I have noticed it to be about impossible to get the oil temp over 150. CHT's are 405 to 410 in cruise and higher in the climb. I finally got around to taping my oil cooler. I taped 1/2 of the cooler and raised the oil temp to 155. I ended up taping 90% of the cooler and got the oil to 180 and maybe 190 in the climb. Basically I have discovered that the oil cooler is way to efficient for this engine and it is basically a huge air leak for the CHT cooling. I have since been experimenting with a carbon air dam for the cooler which has raised oil temps and lowered CHT temps. In talking to Mitch he said all this is normal and everyone has low oil temps. I am curious what other CC pilots are seeing as far as oil temps and cht temps. Also, does anyone know anything about adjusting the vermatherm to get higher oil temps? My plenum is extremely well sealed. I have also been told to just always run lean of peak which I feel is not a fix. If you are going to run lean of peak all the time why did you spend all the money on a fancy lightweight 180 horse engine? Could have just installed a 320 and ran it normally with no heat issues. The oil probe SB has been complied with.

    Hopefully this helps someone else,

    Jason

  2. #2
    Senior Member Dan L's Avatar
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    Default Re: Low oil temps and high CHT temps..

    Unless the plenum design has changed I don't see how the oil cooler is an air leak for cylinder cooling? They're two separate systems.

    I have a Vernatherm and also cover about 75% of the cooler with an aluminum plate. My oil temps are 160-170 most of the time. Higher power settings and temps of 80 or more with push that up to the 180s. Excessive oil cooling is not a bad thing. That can be managed using these techniques but too little cooling can't be.

    Cylinder temps are rarely above mid 300s.
    Flying Carbon Cub EX #11 since 2011

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    Default Re: Low oil temps and high CHT temps..

    Quote Originally Posted by Dan L View Post
    Unless the plenum design has changed I don't see how the oil cooler is an air leak for cylinder cooling? They're two separate systems.

    2 separate systems using the same cooling air... When the oil cooler is blocked you have more cooling air for the cylinders.

    It is smart to get your oil above the boiling point for water often to get the water out of your oil. Run your engine hard one day, land and open the oil dipstick, watch all the moisture leaving the oil..

    I have seen the inside of engines that spent their life with oil temps at 140-150. Lots of corrosion from the moisture in the oil. Moisture is a byproduct of the combustion process..

    I have a Vernatherm and also cover about 75% of the cooler with an aluminum plate. My oil temps are 160-170 most of the time. Higher power settings and temps of 80 or more with push that up to the 180s. Excessive oil cooling is not a bad thing. That can be managed using these techniques but too little cooling can't be.

    Cylinder temps are rarely above mid 300s.
    2 separate systems using the same cooling air... When the oil cooler is blocked you have more cooling air for the cylinders.

    It is smart to get your oil above the boiling point for water often to get the water out of your oil. Run your engine hard one day, land and open the oil dipstick, watch all the moisture leaving the oil..

    I have seen the inside of engines that spent their life with oil temps at 140-150. Lots of corrosion from the moisture in the oil. Moisture is a byproduct of the combustion process..

    Guess it depends on the power setting, are you mid 300's at say 2,500 rpm? Are you running LOP or ROP or peak EGT? Also would depend on altitude, higher you go less cooling the air can do. My field is at 5,000 and if I am going somewhere I almost always have to climb to at least 10k.

    Thanks,

    Jason
    Last edited by kemper28; 05-22-2016 at 07:10 PM.

  4. #4
    Senior Member Dan L's Avatar
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    Default Re: Low oil temps and high CHT temps..

    what position do you have your gill openings? Mine are in the mid position.

    image.jpg

    At 2500 rpm and 50 degrees ambient I'll be mid to high 300s cht.
    Last edited by Dan L; 05-22-2016 at 08:08 PM. Reason: Correction
    Flying Carbon Cub EX #11 since 2011

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    Default Re: Low oil temps and high CHT temps..

    they are full open... But hard to compare with you because you have a different cowing.. Thanks for the info. I wonder is our oil coolers are the same...

    Jason

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    Senior Member Cubrath's Avatar
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    Default Re: Low oil temps and high CHT temps..

    Jason,

    I have about 12 hours on my EX now. My field elevation is at 4000' so I am similar to you. From the fist hour my oil temp has been rock solid at 167 no matter the ailtitude or power setting. That's with OAT of 60* +/- 10 degrees. No tape on the cooler and my cowl flaps are full open. I started with them at the mid setting and noticed no difference when I opened them full.

    Obviously my CHT's started out high. Now with twelve hours I am seeing low 400's on three and four at 60 percent power, 50 ROP at 5000'. I can't do a full power climb for over five min right now without over temping. I'm hoping that will get better as the engine continues to break in.

    Mike

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    Senior Member TroyBranch's Avatar
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    Default Re: Low oil temps and high CHT temps..

    This is an interesting tread. I really thought that cylinder temps would be really cool with this set up. I guess the high compression piston make a quite a bit of heat. My RV10 runs in the low 300s and will only get in the 400s on a really hot day and climbing to steep. Having to stop a full power climb because of temps will be a pain. You should be able to leave it and forget at full power in trying to get out of a valley in big mountains. Hopefully it will get better Mike, oil consumption should be stable now and temps should keep dropping. But at 65 hrs Jason, your break in is done... I thought that there was crazy amounts of silicone to really seal the lower fins, but maybe it really does need it. Not sure if you sealed the lower areas.

    Oil temps should always be over 180. 180 to 210 is a nice range. If you are below 180 I would be taping off the cooler. Sounds like a shutter to stop the air flow through the cooler controlled from the cockpit is a really good idea. Less flow through the cooler will put more flow through the cylinders so I agree with blocking off the cooler will lower cylinder temps.

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    Default Re: Low oil temps and high CHT temps..

    Hi all, I may be off on this thought but seems to me the discussion might be apples and oranges i.e. older planes vs newer ones re resolving the oil temp issues. The older planes did not come with a vernatherm. As a result covering the oil cooler or closing cowl flaps worked well to increase the oil temps and vise versa. Once the vernatherms were standard on the newer planes (I added one to #246 to fix the issue) as I understand it, the valve stays closed and does not circulate to the oil cooler and therefore oil temps rise until the vernatherm valve opens at the 180 degrees (or whatever set temp on the valve) and stays there unless the oil cooler is not doing its job. That said on my new plane #400 which has a vernatherm I too noticed that the oil temp stays at 167 ( my older plane #246 with the later installed vernathern sits rock solid at 180) which seems to me maybe the vernatherms have been set to a temp less tan 180??? Maybe Mitch or Randy have a factory answer and if I am way off on this sorry for adding any confusion. Best Gary

  9. #9
    Senior Member Dan L's Avatar
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    Default Re: Low oil temps and high CHT temps..

    My EX is an older, original version but I do have a Vernatherm installed. My understanding is that the valve still allows some oil through the cooler so it can't congeal in the cooler. Covering the cooler helps get the temperature up even with a Vernatherm.
    Flying Carbon Cub EX #11 since 2011

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    Default Re: Low oil temps and high CHT temps..

    Quote Originally Posted by kemper28 View Post
    2 separate systems using the same cooling air... When the oil cooler is blocked you have more cooling air for the cylinders.

    It is smart to get your oil above the boiling point for water often to get the water out of your oil. Run your engine hard one day, land and open the oil dipstick, watch all the moisture leaving the oil..

    I have seen the inside of engines that spent their life with oil temps at 140-150. Lots of corrosion from the moisture in the oil. Moisture is a byproduct of the combustion process..

    Guess it depends on the power setting, are you mid 300's at say 2,500 rpm? Are you running LOP or ROP or peak EGT? Also would depend on altitude, higher you go less cooling the air can do. My field is at 5,000 and if I am going somewhere I almost always have to climb to at least 10k.

    Thanks,

    Jason
    Hi Jason, yesterday I tried removing the dipstick, as you mention. It was really impressive to see all that steam. So much so that I decided not to screw it back, but instead made up a gauze cap with remove before flight tape attached so that it can ventilate while in the hangar.

    Does anyone see anything wrong with this practice?

    My oil temps are low, 150 - 160, so I will tape up the cooler. Especially since I just received an oil test result showing the metals are trending up over recent tests which they say will be due to corrosion from water in oil.
    Paul.

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