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What is normal range for CHT on 912 ULS?

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5 years 9 months ago - 5 years 9 months ago #6589 by Stevepattinson
What is normal range for CHT on 912 ULS? was created by Stevepattinson
I understand the max is 150 deg C but is there a 'normal' cruise range. I am currently cruising at 83/78 on the 2 cylinders with probes. As we go into winter, what would be considered too low?
Last edit: 5 years 9 months ago by Stevepattinson. Reason: Typo

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5 years 9 months ago #6595 by billmartin
Replied by billmartin on topic What is normal range for CHT on 912 ULS?
Steve,

That is about the same temp range as my engine at cruise. So far, I haven't seen a lot of drop in temps with winter flying. A friend of mine uses the high tech solution of duct tape on the radiator but so far I haven't seen the need to do anything.

Bill.

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5 years 9 months ago #6596 by Stevepattinson
Replied by Stevepattinson on topic What is normal range for CHT on 912 ULS?
Thanks Bill, lets see how winter goes. I have just put a sleeve on the oil radiator so I can get it up to 100.

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5 years 8 months ago #6713 by kappi
Replied by kappi on topic What is normal range for CHT on 912 ULS?
Hi Guys....I am running a new 912uls with revised heads and I have a higher cht limit and I am told it is due to the probes now running directly in water and no longer in a air void (older engines)----before 95 degrees c and now 105 degrees c......hope this is ok....anyone with knowledge about this please advise and why do these engines run without a thermostat???
BR ...Kappi

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5 years 8 months ago - 5 years 8 months ago #6714 by Roger Lee
Replied by Roger Lee on topic What is normal range for CHT on 912 ULS?
Hi Andy,

The 105C (221F) should be fine and is more accurate now with your new heads. What are your CHT's running? If you are using a 50-50 coolant mix then 248F should be the max temp. Some of the coolant temps from plane to plane will differ because of radiator size and air flow over the radiator which of course depends on radiator placement and of course OAT. Winter time coolant temps will be much lower than hotter summer temps. It will be different with Evens coolant verses 50-50 and there are a couple other minor factors. You're better off with 50-50.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last edit: 5 years 8 months ago by Roger Lee.
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5 years 8 months ago #6715 by billmartin
Replied by billmartin on topic What is normal range for CHT on 912 ULS?
Andy,

Kevin mentioned a device for thermostatic control under the general discussion heading. I haven't used one myself but have seen them in operation. They work like the oil thermostats in that they bypass fluid around the radiator. If they fail, they simply no longer bypass and you run cooler. Pretty much failsafe and easy to install.

I have never had to use anything like that in my system. My engine is a fully exposed pusher installation and the temps do fluctuate summer to winter but never enough to be a problem since our winters in NC are usually pretty mild.

Odd as it sounds, one thing that will bring winter coolant temps up somewhat is an oil thermostat. Easy to install, relatively cheap, and they consideradably shorten your preflight warmup time.

Bill.
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5 years 8 months ago #6716 by Roger Lee
Replied by Roger Lee on topic What is normal range for CHT on 912 ULS?
Hi Andy,

Coolant temps and CHT temps aren't that important on the low end. I tend to pay attention more to oil temps and EGT's. So long as you aren't over heating don't worry about low coolant and CHT's. If you want to bring them up then you can use a thermostat, but for me they are always in the way when I want to do maint. so I use the cheapo method and just put a strip of 2" aluminum tape across my radiator. My radiator and oil cooler are back to back so it helps both. I put it on in November and take it off the the end of Feb. (your winters and cold temps may certainly be worse) my oil temps stay around 210F-215F and CHT around 200F. A few bucks in tape for 20 times (20 winters) is a lot less than $200-$600 for the thermostat.

I really boils down to a personal choice and anyway you go works just fine.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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7 months 16 hours ago #20927 by frednorthup@allstate.com
Replied by frednorthup@allstate.com on topic What is normal range for CHT on 912 ULS?
What if these temperatures vary from side to side? Same with the EGT are running around 100 Degrees different. OAT low 20 F.

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7 months 10 hours ago #20934 by Roger Lee
Replied by Roger Lee on topic What is normal range for CHT on 912 ULS?
CHT's typically run 5F - 20F apart. The EGT's depending on the gauges, system setup, throttle style type ect..are usually around 15F - 80F apart. You can see an EGT bounce a bit over 100F at different throttle settings. Part of this is why we sync the carbs, clean the air filters and use good maint. practices.

Throttle types play a big part here some times.

Roger Lee
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Tucson, AZ Ryan Airfield (KRYN)
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5 months 2 weeks ago #21427 by frednorthup@allstate.com
Replied by frednorthup@allstate.com on topic What is normal range for CHT on 912 ULS?
Roger
It is cold here with OAT in 10 to 25F and sometimes I see EGT over 200 F apart. Kitfox factory says egt are not a factor. I have read here that one side might be richer than the other. The plugs are burning very similar and the engine runs good with other temps normal. should I make any adjustments?
Is it better for the engine to run CHT in the higher range? I imagine for the heater to operate at max the temp would to be in the higher range?

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5 months 2 weeks ago - 5 months 2 weeks ago #21435 by Roger Lee
Replied by Roger Lee on topic What is normal range for CHT on 912 ULS?
"It is cold here with OAT in 10 to 25F"
Move to Arizona. :) 71F tomorrow. Burrrr. I need a jacket. LOL
It's better to see oil in the 200F - 220F range. There is no minimum for CHT's in the book. A 200F spread is a little unusual. It could be air flow to one carb different from another or maybe someone has tinkered with a carb needle clip position or maybe an EGT probe isn't doing a good job and going bad. It would be helpful to know more about the EGT. Were they ever equal, does the OAT's always affect them like this, did this just start, has there been any recent maint.? Normal EGT's tend to run between 0-80F in differential. Occasionally some see a little more depending on your system and engine setup.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last edit: 5 months 2 weeks ago by Roger Lee.

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5 months 2 weeks ago #21439 by frednorthup@allstate.com
Replied by frednorthup@allstate.com on topic What is normal range for CHT on 912 ULS?
Yeah yeah I am used to the cold . The kitfox is a bit drafty Ill tell ya. The plane is new to me in August and I did not notice any big difference then.
It seems to run fine and the plugs are burning similarly . The oil temp is good I just keep adding or removing tape. I am thinking I can tape the radiator as well to increase Temp of the cabin heater. Could I switch the egt sensors and see if it still reads high? I am thinking one side is getting more cold air over the heads ,I wonder if the prop actually pushes more air through the right side? Air to the carbs goes into a manifold so I don't see that being different from one to another.
So basically all I can do it monitor it and check a few things. The plugs could be changed as they are getting near 100 hours.
Thank for the input

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5 months 2 weeks ago #21444 by Roger Lee
Replied by Roger Lee on topic What is normal range for CHT on 912 ULS?
The cooler air flowing over the engine isn't affecting the EGT's. That comes from fuel burn exiting out the exhaust port. You can put tape over the oil cooler or the coolant radiator. Over the coolant radiator will affect the CHT's. You might want to check the plug gaps. In your colder weather set them at .023. The books says .023 - .027. .027 is too wide for you this time of year and the narrower gap may be more beneficial with starting and a better burn. Don't forget the thermal paste on the plug threads. Cold dry air makes for a leaner mixture.
You could switch them or at least the connections. It would at least let you know if it's a sensor or a correct reading.

www.rotax-owner.com/en/videos-topmenu/ro...ute/399-2-oil-inj247

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
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5 months 2 weeks ago #21461 by frednorthup@allstate.com
Replied by frednorthup@allstate.com on topic What is normal range for CHT on 912 ULS?
I will check the gap .Can you tell me how often the sparks should changed?

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5 months 2 weeks ago #21463 by Roger Lee
Replied by Roger Lee on topic What is normal range for CHT on 912 ULS?
First we have two brands of plugs now so I'll address the NGK's first. The NGK's are the most prolific. This is going to be a fairly debatable subject with many personal opinions. So here goes and you may here from others. The book says up to 200 hrs. and re-gap them at 100 hrs and clean them. These need to be gapped right out of the box and thermal paste applied. Now no one that I know goes to that length. These are only a couple of dollars each. Everyone I know tosses them at 75 hrs. and no one I know goes past 100 hrs.

Now the new Rotax plug is $22 each and I'm sure people will go up to the 200 hrs. These do not need to be gapped out of the box, but thermal paste still needs to be applied.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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5 months 2 weeks ago #21465 by kenryan
Replied by kenryan on topic What is normal range for CHT on 912 ULS?

Roger Lee wrote: ... The NGK's are the most prolific... These are only a couple of dollars each...the new Rotax plug is $22 each...


And it is my understanding that the NGK plugs are fine, that the reason Rotax stopped using them was simply that NGK wanted out of the airplane spark plug business (but they are still manufactured for other applications) and there is nothing "better" about the super expensive Rotax plugs.

Please correct me if I'm wrong.

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5 months 2 weeks ago #21467 by frednorthup@allstate.com
Replied by frednorthup@allstate.com on topic What is normal range for CHT on 912 ULS?
Good info. I am way over 100 hours on this set going by the old guy's log. I already have a new set ready to in>


Thanks again

Wow $22

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5 months 1 week ago #21518 by jiott
Replied by jiott on topic What is normal range for CHT on 912 ULS?
I have been inspecting/cleaning and regapping my NGKs at 100 hours and replacing at 200 hours for 6 years and 700 hours now on my 912uls with no problems. I use non-ethanol mogas almost exclusively.

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