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CHT variations in Superior 0-360

A

Andrew Hamilton

Member
Cylinder 2 & 4 run @ 185 C
Cylinder 1 runs cooler @ 175 C
Cylinder 3 runs hotter @ 195 C
Is this OK ? Should they all be closer ?
Could it just be differences in the sender units to the Dynon
Older planes only monitor one cylinder so am I worried about nothing.
I would appreciate some thoughts.
 
Welcome

Andrew

Firstly welcome to VAF there's a lot of good info here.

Check a previous thread:

http://www.vansairforce.com/community/showthread.php?t=47542

It should have the info you need.
Looking at the figures you give a small dam in front of number 1 cylinder should even up the temps nicely.
It would be fine to leave it as is but I like having them nearly even as then I can easily spot if somethings changed. Makes it much easier to spot a plug problem etc if you know that normally the're all the same.

Peter
 
Last edited:
gap behind #3

Andrew

Forgot to add it's worth putting a washer between the back of #3 clyinder and the baffle to create a gap which helps cooling and lowers #3 CHT's.

Peter
 
Gap behind #3 sounds a good idea

Thanks Pete, that sounds a good idea. Without it the area around #3 is a bit of a trap with no where for the air to go. The #2 & #4 side should have better air flow as there is a shallow ramp in and better flow past the oil cooler. On the #1 & #3 side the ramp in is steep (faster flow over #1 making it cooler) and the dead area behind #3 could explain my problem with a hotter #3. It sounds good in theory, I'll give it a try - thats why its called EXPERIMENTAL.
Interesting that in the link you posted a lot of people reported a hotter #1 cylinder which doesn't fit the theory but I'll try the gap anyway.

Many thanks,
Andrew
 
forgive me for the simple minded question

for temps that are close-- like these. Why not try changing the location of the cht probes to test whether the temperature (if not at least the trend) moves with the probe?

This type of troubleshooting is routinely done in larger aircraft and works well to differentiate between broken parts, faulty wiring, rigging, adjustments etc.
 
Tape

Andrew,

I had the same situation on my Superior 360. I used a piece of the aluminum duct tape to make a 1" high dam on the #1 cylinder and everything evened out. I already had the spacer on the back on #3. I meant to make a permanent air dam on #1 to replace the tape but that was 200 hours ago and I still haven't gotten it done yet.

Andy
 
I have a Superior O-360 with a fixed pitch prop. My cruise CHT's settle out at at about 330F (165C) for cylinders 1,2 and 4. Cylinder 3 runs about 340F(171C). I do have a 1 inch dam in front of cylinder 1 but no washer behind cylinder 3. Before I put the dam in place the CHT's spread was was similar to yours, although the temperatures were a little lower. I plan to try the washer behind cylinder 3 next week. My slightly lower temperatures may be partly due to my fixed pitch prop not typically making as much power as the variable pitch and I almost alway fly at 7K to 8K ft. where it's cooler. Overall I think your temperature spread is typical.
 
1/4 inch of tape can make a big difference

My number 3 is the coolest right now. The I have some tape on each front cylinder, had been trimming it down on #1 to even things out and went to far. Added .25 inch onto #1 and it is crazy how much difference that made. Don't forget that EGTs are a factor as well.

Hans
 
instructor_bill said:
for temps that are close-- like these. Why not try changing the location of the cht probes to test whether the temperature (if not at least the trend) moves with the probe?

This type of troubleshooting is routinely done in larger aircraft and works well to differentiate between broken parts, faulty wiring, rigging, adjustments etc.
Click to expand...

Bill,

If you are talking about moving the probes to different cylinders, that is always worth a try. (For those who do not know, the cylinders have a threaded receptacle for the CHT probes, thus there is only place to install them on each cylinder.) However, as closs as the temps are, they are probably OK.

After that, I would try:
1. Cleaning out the flashing between the cooling fins on the cylinder heads
2. RTV any gap in the baffles
3. Add the aforementioned washer behind cyl #3
4. Block the space under the cowl inlet ramps so air cannot pass under them (I used blue Great stuff foam, worked great)
5. Make sure the airseal fabric is sealing (Look at the top of your cowling for where it makes contact, that is a good ?tell?.) and adjust as needed
6. Put some aluminum tape on the front of cylinders #1 & #2. This will force some air up over the front cylinders and into the back.

After going through all that, I was able to get all my cylinders down to between 174 to 178*F.
 
I have a Superior O-360 with a fixed pitch prop. My cruise CHT's settle out at at about 330F (165C) for cylinders 1,2 and 4. Cylinder 3 runs about 340F(171C). I do have a 1 inch dam in front of cylinder 1 but no washer behind cylinder 3. By Brad
Click to expand...

Brad,

I have almost identical temps on my 9A FP with O320 Lyc. I also have a small (1.5 inch high) aluminum foil air dam in front of cylinder #1 but no spacer behind #3. Without the dam on #1, that cylinder temp goes down 15 - 20 degrees F. I also have my cabin air takeoff directly behind (above) cylinder #3which probably prevents some of the airflow from going down through the cylinder fins. I'm curious to hear how your adding the spacer behind #3 affects that cylinders temp. If in fact it does cool it down significantly I will also try same.
 
Joe

If you look at the back of the #3 cylinder you'll see that the fins on the head are very short. If the baffle is hard against them no air is able to flow to the fins on the lower 1/2 of the cylinder. Creating a gap allows some air to pass and cool the lower fins improving the CHT.

Hope this makes sense

Peter
 
Problem solved

Thanks to all for your ideas and suggestions. I built a small dam in front of #1 cylinder using 3/4 X 3/4 X 0.032 angle which was left over from my kit and placed a washer behind the baffle at #3 cylinder.
In a quick test flight yesterday at low altitude the CHT's all were within 5 deg.C which was very pleasing and I think it will improve in a cruise.
Your help has been much appreciated.
Andrew.
 
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