Cylinder Head Temps

[Whack777]

I'm running a Jabiru 2.2 and getting some variation in CHT's between cylinders. Just wondering if there are many of you monitoring all 4 cylinders at once and if so, what sort of variations you are getting.

 

Cylinder No 4 is consistantly warmer than the other 3 (but there are varieations between them as well). It would be interesting to know what others are finding.

 

If I had a single monitor and had chosen to connect it to cylinder #1, I would be thinking the motor is running as cool as a cucumber. If I just were monitoring Cylinder #4 I'd be thinking it was running on the warm side.

 

.... anyway look forward to some of your findings.

 

Regards

 

Wayne

 

 

[Whack777]

Correction

 

Correction to the above. It is actually the No 2 Cylinder which is the warmest. (ie Front right hand side when facing the plane).

 

 

[facthunter]

Head Temps.

 

How big is the variation and what are the actual temps?..Nev...

 

 

[Bruce Tuncks]

jab 2.2 chts.

 

I put senders on all 4 cylinders and wired them thru a rotary switch to see each in turn.No 4 runs hottest, but not by more than 5 degrees or so. But i am running with the big finned heads on the back (3 and 4) with older heads on the front cylinders.

 

The other jab I know of which monitored all chts like this finished up with deflectors to divert air past the front cylinders to even up the temps.

 

cheers, Bruce

 

 

[Whack777]

How big is the variation and what are the actual temps?..Nev...

Hi Nev,

 

I have mislaid my notes and so can't be too specific. I know that in cruise 1 cylinder reads between 100 - 110 deg another is in the 120's another in 130's and the hottest around 155 deg. In a long extended climb (6000ft) the hottest cylinder (No 2) stabilised around 181 deg (Normal climb usually in the 170's)

 

Bruce,

 

Thanks for that... only 5deg variation in your temps...

 

Wondering if I might have a monitoring issue???

 

Regards

 

Wayne

 

 

[vk3auu]

I would be surprised if you were not getting at least a 5 degree variation. The temperature measuring system probably isn't accurate to that amount anyway.

 

David

 

 

[facthunter]

Temps.monitor

 

Wayne, someway you have to be sure that your method of measuring provides a consistent result, yet you have to make them under identical conditions, therefore ,at the same time. This is not easy. I wouldn't worry about a 10 degree variation. I like the idea of a rotary switch, (in principle, I wouldn't buy one, just hook up some wires)...Nev

 

 

[Bruce Tuncks]

Wayne, I agree with the comment about how the accuracy of my measurements can't be that good. What I actually notice is very little change when I move the rotary switch, with no.4 being a little hotter. There is something wrong if your no.2 is the hottest. Have you tried dunking each sender into boiling water to see if they all read 100? Then there is the possibility that a tiny leakage at the no2 sender is causing those readings.

 

cheers, Bruce

 

 

[Whack777]

Thanks Guys,

 

Will look into it a little more.... test the senders with boiling water and then get some more data.

 

Rgds Wayne

 

 

[Yenn]

Another cause of error could be in the rotary switch. It would not take much difference in resistance in the contacts to give on odd reading, but of course the gauge is the same for all and they usually vary.

 

 

[Guest imap8ntr]

My hottest CHT in my 3300 upon climb is about 174 deg. All others are lower progressively from back to front. I noticed that there is about a .5-1.0 inch space between the factory baffles and the cowl air intake holes. Do you think that placing some rubber baffling material around the forward end of the baffles to stop air from going around the sides of the CHT cooling baffles will lower my CHT's? I have had good success with this rubber baffle material around the oil cooler inlet.

 

Thanks

 

Ivan

 

 

[Yenn]

I thimk you will find that Jabiru recommend rubber baffles to prevent outflow of air at the front of the shrouds. In fact when I bought my motor they provided the strip of rubber.