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Bruce Tuncks

Jabiru cooling

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22 minutes ago, Yenn said:

Where is old K involved in this conversation?

Left Right Out!

I did a little bit of experimenting on my own installation a few years back, partly inspired by Dafydd Llewlelyn's work testing the CAMit engine. Like much in life, I learned just enough to be dangerous. Based on my experiences, I suggested that in-flight cameras should record all the data, so the pilot can concentrate on what he should be doing.

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Why I asked that question is because I suggested something and others said it came from you Old Koreelah.

If my ideas don't work you will get the blame!

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I made quite a few changes to my cowls and oil cooler position which have resulted in cool CHTs.  CHT on number 4 (generally the hottest) gets to about 130C on taxi  then drops to about 105 or less in the air.  I climb out at 80-85 knots @ 700fpm or better. Laurie

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Keenaviator, thanks for your reply... please tell us more about what you have done. 

Just today, I have put a 32mm ribbed hose between the 2 ducts, as suggested by oldK  who was right about how the difference between the RHS and LHS ducts should be measured. The measurement showed 45mm of water head difference.

Tomorrow I will fly with a connecting duct in place. My hope is that it will equalize things .

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2 hours ago, Bruce Tuncks said:

Keenaviator, thanks for your reply... please tell us more about what you have done. 

Just today, I have put a 32mm ribbed hose between the 2 ducts, as suggested by oldK  who was right about how the difference between the RHS and LHS ducts should be measured. The measurement showed 45mm of water head difference.

Tomorrow I will fly with a connecting duct in place. My hope is that it will equalize things .

Next time I'm at the hangar with the cowls off will take photos outlining what I've done.  The balance scat hose between the cooling ducts sounds like a good idea too. The main thing I did was reduce the pressurising of the lower cowl be moving the oil cooler to the rear of the engine, ducting air to it from another vaca duct on the right hand side of cowl. I can control this air to the oil cooler from the cockpit - monitoring oil temperature. 

Edited by Keenaviator
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10 hours ago, Bruce Tuncks said:

Keenaviator, thanks for your reply... please tell us more about what you have done. 

Just today, I have put a 32mm ribbed hose between the 2 ducts, as suggested by oldK  who was right about how the difference between the RHS and LHS ducts should be measured. The measurement showed 45mm of water head difference.

Tomorrow I will fly with a connecting duct in place. My hope is that it will equalize things .

Bruce I'm blushing get the credit for such a good idea, but it wasn't me who suggested this.

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11 hours ago, Bruce Tuncks said:

Keenaviator, thanks for your reply... please tell us more about what you have done. 

Just today, I have put a 32mm ribbed hose between the 2 ducts, as suggested by oldK  who was right about how the difference between the RHS and LHS ducts should be measured. The measurement showed 45mm of water head difference.

Tomorrow I will fly with a connecting duct in place. My hope is that it will equalize things .

Bruce I hope this works for you but the turbulence, drag caused by the 32mm holes in the duct might reduce total airflow. Just a thought. 

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The turbulence caused by the holes would be minimal as there is flow through them from low to high, but should be little flow across them.

I wait to hear what happened.

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Today I tried the ribbed hose connecting the 2 ducts. I took a picture of how it looks.

I reckon it worked well! The manometer ( measuring between the ducts ) showed about 12mm difference, well down from the 45mm difference before the connecting hose.

The day was cool, ambient=18 degrees and overcast.

On climb, T1=128 T3=139 ( the cooler RHS)

T2=153 and T4=151 ( the warmer LHS )

 

There are a few other things to do...

1. do the test again on a hotter day... adding 17 degrees for a 35 degree day puts that T2 at 170 degrees.

2. putting a deflector in front of no1 cylinder to stop it being so cool

 

IMGP0806.JPG IMGP0818.JPG
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Sorry Yenn, I must have had a senior's moment when I attributed your good idea to Old K. But your and old K's  planes look very similar on your icons, maybe this is why I mix you up sometimes. Anyway, thanks for the good suggestions. And  old K is no slouch either. I'm in my 70's here and guess you guys are close behind, age-wise that is.

I know I am being real fussy trying to get the temperatures all exactly equal, but it is fun and I reckon interesting too. I love it when a bit of real progress happens.

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Bruce you are just a young bloke. I hope you get it all where you want it.

It appears that the left bank always runs hotter than the right with Jabs, probably something to do with the rearward position of the inlet.

Good cooling depends upon the air flow being close to the fins. Anywhere air can flow without going between the fins reduced the efficiency. Lycomings usually have ducting close to the fins beneath the cylinders to stop air exiting directly downwards and force it around the lower part of the cylinder.

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