Thread: CTLS-Cylinder Head Temprature

Hi
After much haggling with the Israeli Authorities (which took almost a year) The Israeli Flight Design Dealer has at long last secured a temporary C of A for my new CTLS. Have flown it for a number of hours in the desert and found that the right CHT is constantly 20 Degrees hotter than the left and above about 4600 Revs tends to creep into the yellow (230-235). I have accordingly gone slow and have asked the Israeli dealer to look into the matter. He could not identify any problem with the engine and thought that this may be because the temperature gage is at the back of the engine where there is less air flow. Apparently the Texan has a modification to address this issue. I was wondering whether anybody else has encountered this problem in warm weather flying?.
Otherwise it's a great plane to fly and am waiting for full certification within the next month or so.
Richard Luthi

Hi Richard,

The max CHT is 135C (275F) and 120C (248F) if you are using 50/50 mix of coolant, which you most likely are using. So you can fly at your 112C (234F) if you want to and it won't hurt the cylinder at all. The reason the CHT is set at 120C for 50/50 coolant is they are worried that there might be a hot spot and cause a vapor space by the cylinder and cause it to over heat in that one spot and it wouldn't show up on your gauge. A 15F-20F spread can and may be normal. Just to rule out a coolant issue you might want to take a good look at the coolant hose for that cylinder and make sure it does not have any type of a hard bend in the hose that might cause a flow restriction. If you do have a pretty good bend or think it has a reduced flow then replace the hose and make the set up with no hard bend.
I live in Tucson, Arizona and the day time temps here right now are about 38C+ (100F+). What are your day time temps right now? The CHT's can get up there. Your engine should run cooler at 5000-5300 rpm and it is set up to run a little cooler because it gets more fuel. It tends to run a little hotter in low mid range rpm around the 4600 rpm. Watch the EGT's and they should go down as you give it more fuel.
Check to see what your wide open throttle (WOT) rpm are. Hold WOT for 1 minute. It should be around 5500 rpm. The prop setting can have a significant impact on temps depending on where it is set for pitch.

Hey guys!
Theoretically the cylinder head temperature should be very close to being the same considering the temperature of the coolant inside all 4 of the heads is more or less the same after leaving the water pump. Keep in mind that the left CHT is measuring off of the #2 cylinder which is at the front of the engine and your right side is measuring off of the #3 cylinder which is at the rear of the engine, I would imagine that the difference in airflow of the front and rear cylinders is enough to cool the head bodies differently.

Hi Jeremy,

That's why I think his 15F-20F temp different is normal. They may be close to 235F or more and CHT temps can be affected by outside air temps, prop pitch or he may be using Evans coolant?

Dear Roger and Lee
Thanks for the quick response. OAT was over 35C, which is similar to your conditions. What got me worried was the change from Green to Yellow, which led me to think that whoever decided when the color should change (Over 230) must have known what he was doing. I could find no problem in the coolant pipes- but will probably fly tomorrow and see whether higher revs will cool the cht and resolve the issue. My mechanic suggested switching the wiring between cylinder 2 and 3 and seeing whether the reading is reversed. This should confirm whether the No 3 sensor is to blame. What do you think?
Regards
Richard

Hi Richard,

I wouldn't loose any sleep seeing the CHT in the yellow. The max only for 50/50 mix coolant purposes is 248F. The engine itself can handle more. You may see it in the yellow on climb, but I would think it may cool a little straight and level in the 5000-5200 rpm range.

My CHT spread has been as high as 11F in Florida with 91F ambient temperature.

Originally Posted by Jeremy CPS

Hey guys!
Theoretically the cylinder head temperature should be very close to being the same considering the temperature of the coolant inside all 4 of the heads is more or less the same after leaving the water pump. Keep in mind that the left CHT is measuring off of the #2 cylinder which is at the front of the engine and your right side is measuring off of the #3 cylinder which is at the rear of the engine, I would imagine that the difference in airflow of the front and rear cylinders is enough to cool the head bodies differently.

Which of the front cylinders is #2 and which of the rear is #3?. Also on my D120 I have two CHT readouts. Is the top readout the #2 or #3? I seem to have a loose or bad senser on one because the reading jumps around from no reading to normal.

One reason we can see higher than normal temperature differences between cylinders is too much coolant in the mix.

Originally Posted by pilot1950

Which of the front cylinders is #2 and which of the rear is #3?. Also on my D120 I have two CHT readouts. Is the top readout the #2 or #3? I seem to have a loose or bad sensor on one because the reading jumps around from no reading to normal.

Left/front [top on EMS120] is #2
Right/rear [bottom on EMS120] is #3.
usually I can see a maximum 10C difference betwen those 2 readings.

erratic readings:
check connections between terminals and cables [under the heatshrink - I also have had a loose one].
or you can swap the cables [eventually temporary prolong them] for sensors to narrow the problem [bad sensor or bad connection].

good luck,
alec