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BobbyPaulk(at)comcast.net
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 Posted: Tue Aug 26, 2014 5:46 am Post subject: CHT'S |
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Guys
I really appreciate all the very useful information.
I have added an aluminum lip extension and it helped. I went back and made it permanent with fiberglass.
I have changed probes with no significant changes. I increased the height of the ram air ducts and put the wires inside and added baffles. All of this has made for better CHT's.
My #2 cylinder runs about 255 to 265 in cruise ( very nice ) #1,3, & 4 run in the 270's to 280.
Number 5 and 6 run 310 to 320 in cruise due to high EGT's. Cylinders 1 thru 4 run 1200 to 1250 at 2700 RPM. #5 & 6 run about a hundred degrees hotter 1350 ~ 1360. I believe it is caused by the uneven fuel distribution in the induction manifold. I have tried tilting the carb many times without much success. I have changed the inlet to fiberglass duct with several different dividers. I have also changed jets many times trying to find the right combination.
I am contemplating going even richer to get a lower EGT on #5 & 6.
I believe the sharp ninety degree turn right after the carb discharge makes it difficult for the heavier ( richer ) mixture to turn the corner so the better mixture sails on down to the other cylinders.
This has been an ongoing experiment since the first flight.
Bobby ( age 76 )
Zodiac 601 XL "B"
Jabiru 3300 S/N 1141
Sensenich 64" x 51" Prop
Bing Carb 260 Main & 290 Needle Jet
Status - Flying 222 hrs.
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ftyoder(at)yoderbuilt.com
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| Posted: Tue Aug 26, 2014 2:48 pm Post subject: CHT'S |
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Sounds like good progress. Have you checked the head bolt torque at 20# since the last mods with the lower CHT's? What was your cruise RPM with the EGT's you cited below? I think 1350 is okay but richer could lower the CHT's
Tim.
From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of BobbyPaulk(at)comcast.net
Sent: Tuesday, August 26, 2014 6:46 AM
To: Server, JabiruEngine-List Digest
Subject: CHT'S
Guys
I really appreciate all the very useful information.
I have added an aluminum lip extension and it helped. I went back and made it permanent with fiberglass.
I have changed probes with no significant changes. I increased the height of the ram air ducts and put the wires inside and added baffles. All of this has made for better CHT's.
My #2 cylinder runs about 255 to 265 in cruise ( very nice ) #1,3, & 4 run in the 270's to 280.
Number 5 and 6 run 310 to 320 in cruise due to high EGT's. Cylinders 1 thru 4 run 1200 to 1250 at 2700 RPM. #5 & 6 run about a hundred degrees hotter 1350 ~ 1360. I believe it is caused by the uneven fuel distribution in the induction manifold. I have tried tilting the carb many times without much success. I have changed the inlet to fiberglass duct with several different dividers. I have also changed jets many times trying to find the right combination.
I am contemplating going even richer to get a lower EGT on #5 & 6.
I believe the sharp ninety degree turn right after the carb discharge makes it difficult for the heavier ( richer ) mixture to turn the corner so the better mixture sails on down to the other cylinders.
This has been an ongoing experiment since the first flight.
Bobby ( age 76 )
Zodiac 601 XL "B"
Jabiru 3300 S/N 1141
Sensenich 64" x 51" Prop
Bing Carb 260 Main & 290 Needle Jet
Status - Flying 222 hrs.
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dons701
Joined: 22 May 2009
Posts: 80
Location: Hershey, PA
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| Posted: Wed Aug 27, 2014 8:07 am Post subject: Re: CHT'S |
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Hi Bobby
What is your full throttle climbing rpm? What is your egt's at this rpm? By your description of cylinder head temperatures it appears you could benefit by allowing more airflow past the front cylinders, assuming you have baffles to trim. This should help send more air to the rear cylinders. ....DonB
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Zenith 701 #76120
Jabiru 2200A #2456 95 hours
Sensenich Wood 64-PJ-36 Prop |
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dons701
Joined: 22 May 2009
Posts: 80
Location: Hershey, PA
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| Posted: Wed Aug 27, 2014 12:19 pm Post subject: Re: CHT'S |
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Bobby, I forgot to ask if you have made sure the back of your ducts are extended to wrap around the bottom of your cylinder heads slightly as this would utilize what energy is left from cooling air flow. ....DonB
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Zenith 701 #76120
Jabiru 2200A #2456 95 hours
Sensenich Wood 64-PJ-36 Prop |
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