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Thread: Dual STI build log

  1. #361
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    Default Re: Dual STI build log

    Brian I am not running a thermostat as I figured I would be running into heating issues. I think the biggest thing is by dropping the lip and giving more exit air, its really doing its job. The heat exchanger was to help bring down the oil temps as I figured they would be running hot. It should also bring up the oil temps when the water temp is higher than the oil. With CHT at 180 and oil at 130 the heat ex-changer is heating the oil and cooling the chts. I will have to try and fly it when OATS are a little warmer and get some better numbers. I was building as fast as I could to try and get it up flying in the heat.......oh well. I may need to look into running a thermostat. Why did you run the thermostat that you did? Do you happen to have a part number for it?
    Last edited by Shadowrider; 09-30-2019 at 07:10 AM.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  2. #362
    Senior Member aviator79's Avatar
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    Default Re: Dual STI build log

    I ran the thermostat with a higher setpoint for two reasons:
    1) Normal operating range of the oil is 190-230 F. I'm not sure why the setpoint on the commonly sold thermostat is 180 deg F, but it seems too low, especially given that some oil will always flow through the oil cooler, so when it's chilly, the thermostat won't be able to regulate right at its setpoint.
    2) Looking around at my Kitfox bretheren, most had more issues getting the oil warm than trying to keep it cool, with many 912 operators installing shutters in addition to the thermostat. A higher setpoint lets you actually get to temp before your thermostat starts opening, so you have a better chance of hitting 190.

    Caveat: If its's really cool, or you have really good flow across your cooler, then there is some point at which your thermostat can't regulate at its setpoint. The thermostat always lets some oil flow through the cooler, so even when it's "fully closed" you may not be able to keep the oil at the setpoint. I've been pretty lucky that even when it's pretty dang cold out, I have no trouble getting into the normal operating range on every flight. When it's cold, it may stabilize below 190 in cruise, but I guarantee I'll hit 205 on takeoff/climb. This isn't due to great design on my part. I picked a thermostat based on intuition without analysis, and got lucky. \

    As a data point: coming back from Phoenix yesterday, at 11,500' 42F ambient temp, 30" MAP/6.5 GPH, oil temp was 190. Obviously your entire setup is very different, so I don't know how useful that is.

    http://www.improvedracing.com/oil-th...tat-p-212.html
    --Brian
    Flying - S7SS

  3. #363
    Senior Member jrevens's Avatar
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    Default Re: Dual STI build log

    It might be good to make this topic a separate thread, but I'd like to add a few thoughts to it now. I have the common oil thermostat sold by Lockwood, Aircraft Spruce, etc. for my 912 ULS. It does have the 180 deg. setpoint, and I think that is probably good, although I think that the thermostatic element in it is also possibly available in other temperature settings, and can be replaced. Even in really cold weather the 180 deg. target of the valve is reached on my engine, but then it drops below that before it closes down again. So on cold days it averages less than 180 deg. It also brings my oil temperature up faster after engine start compared to another friend's without a thermostat, so that is good. Now, to throw out a couple of other points - the common and recommended setpoint of a Vernatherm oil temp control valve on a Lycoming is 180 deg. Lycoming is concerned with moisture in the oil just like Rotax is, and 180 deg. has been shown to do the job. Why? I believe because inside of the engine the oil quickly reaches much greater than 180 deg. on the surfaces of the cylinders, etc. On my Rotax, the oil temperature is measured at the oil pump, after it has left the cooler and before it enters the engine. When it gets inside the engine it quickly gains temperature also, I believe well above the necessary temperature, and water vapor is expelled out the breather system. I also believe that lower oil temperatures (within reasonable limits) are better from a lubrication standpoint, regardless of multi-viscosity oils. I'm sure there is going to be disagreement about all this, but one final anecdote... my friend Stan's original 912 on his Mod. IV, which was a 1200 hr. TBO engine, was outfitted with one of these 180 deg. valves, and that engine (which was still running well) had, I believe, 2500 hrs. on it without any major repairs necessary when he replaced it with a new one last year.

    Oh, I also wanted to say that the thermostatic valve you found looks like a very good one!
    Last edited by DesertFox4; 09-30-2019 at 09:11 PM.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
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  4. #364
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    Default Re: Dual STI build log

    Thanks guys! Trying to figure next steps. I think I finally got prop balanced. Ended up and .09ips. It’s .6ips around 3500 rpms but 4500 and above it smooths our. Flew today and at 9500’ MSL OAT was 33f. Oil temp peaked at 132f and CHTs where 175f. As I leveled off oil dropped to 110f and CHT dropped 155f. I am going to verify oil temp gauges are indicating correctly with a temp gun but I think I have plenty of cooling? I think I am going to start taping off oil cooler and see what that does for me. My new theory is I dropped the naca to clear the turbo and in so do doing I changed the pressure which increased velocity of the air, improving cooling. 🤷
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  5. #365
    Senior Member aviator79's Avatar
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    Default Re: Dual STI build log

    Good idea to verify that oil temp. 110 does seem cooler than I'd expect from dropping the NACA and adding a tripper lip.

    John's points are all perfectly valid. The 180 degree thermostat is probably perfectly adequate for the job.
    --Brian
    Flying - S7SS

  6. #366
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    Default Re: Dual STI build log

    Temp is verified and correct. I taped over the oil cooler with aluminum foil tape. Covered 50 percent and temp only reached 150f oil and 180 water. OAT was 65f. Powered back for landing and temps drop to 110f on the oil and 140f on CHTs. I am going to keep taping up until I get around 180 max temp on oil. I guess it’s easier to restrict cooling than it is to try and add. Did the 3 flight yesterday and still can’t seem to get the prop balanced to acceptable level. Wondering if I have vibration coming from engine possibly? Vibration seems to be higher frequency than the prop rpm. If I let go of stick I see the stick vibrating almost buzzing. I tried to video but it’s not showing up. Going to try changing frame rate. Last time I flew in a kitfox was long enough ago I can’t remember vibration levels.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  7. #367
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    Default Re: Dual STI build log

    Dustin, Just want to make sure you have also checked your prop's tracking. While I run a fixed pitched sensenich I have found that after torqueing its important to check the tracking as well. Just a thought. Bruce N199CL

  8. #368
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    Default Re: Dual STI build log

    Thanks. I did check blade tracking and one blade was off 1/4" out of track. I was able to get it withing 1/16 by adjusting prop in hub before tightening it. Still didn't help balance. Fortunately Steve from Dynavibe spent a lot of time on the phone with me to help to configure and sort through some problems. I did learn that my spinner is really out of balance and sometimes causes issues when trying to balance. I was able to estimate the heavy side of the spinner, rolling it on a table, and put the heavy side on the light sight of prop. I then decided under Steve's direction to take all the weights off and start over for the umpteen time. First run was .80ips. Second run was .30ips. Third run was .05IPS. Steve said to call it at that. He said its hard to get better than that in these light aircraft. I about had a party I was so excited! Time to pull cowl and do I once look over, then its time to head out to the practice area and get the AOA calibrated. Hopefully start putting some time on her now! Oh, I did cover the oil cooler so now there is only about 1" showing. Full power climb and the temp barely got to 160F. Oat was 60F. I think I will probably leave it there for now??
    Last edited by Shadowrider; 10-02-2019 at 08:21 PM.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  9. #369
    Senior Member aviator79's Avatar
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    Default Re: Dual STI build log

    Maybe consider losing the heat exchanger for a thermostat? I guess you could keep both, but weight and complexity wise, I'd try to keep it simple.
    --Brian
    Flying - S7SS

  10. #370
    Senior Member PapuaPilot's Avatar
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    Default Re: Dual STI build log

    That's good news on getting your prop balanced; .05 IPS is very good for a piston engine (I can get the PT6 props a lot better).

    Did you mark relation of your spinner to spinner bulkhead? If not make sure you do, you need to maintain that position for the prop to stay in balance.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

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