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  #1  
Old 09-10-2018, 03:50 PM
Adam Adam is offline
 
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Default Cool CHTs

Guys I have an issue that most people donít, my CHTís run very cool this has been going on for many years and for the most part Iíve been pretty proud that I didnít have an issue of high CHTís. About two years ago I had a sticky valve I had taken care of it and the plane has been flying fine. When I was out at Oshkosh this year I met with Superior Engines and spoke with them for quite a while I told them of my issue with my low temps and their concern was thatís why Iím having a sticky valve as most of my temperatures never get above 300į in Normal straight level flight. Typical temperatures range from about 265į to about 295į cylinders 1 through 4, running 25 square at 4000 feet lean of peak at 78į outside temperature. So my question is what should I do, do, I close up the intake or do I close off the exit part of the cowling. Just a few bits of information this is an RV-8 with an I/O 360 fuel injected with a standard cowl the only thing that is different is I have an exhaust system that is 4 into 1.
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  #2  
Old 09-10-2018, 04:27 PM
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There is a lot in the linked thread (below) about low Vi/Vo inlets, but the standard RV-8 cowl also responds very well to reduced exit area.

http://www.vansairforce.com/communit...ad.php?t=68241
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  #3  
Old 09-10-2018, 05:29 PM
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Carl Froehlich Carl Froehlich is offline
 
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Iíd first verify the accuracy of your CHT readings. As you have a standard Vanís cowl setup Iíd be suspect.

Carl
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  #4  
Old 09-10-2018, 07:16 PM
Adam Adam is offline
 
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Carl, my CHTs and EGTs read the exact ambient temperature when the engine is cold. Spoke to the manufacture and they said there is no adjustment, I really don't think its the probes.
Adam
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  #5  
Old 09-11-2018, 09:54 AM
RV Jerry RV Jerry is offline
 
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I have seen two engines that were supposedly running cool, actual problem was they both had cht senders that did not have a spring forcing the probe to make contact with cylinder so they were just measuring dead air
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  #6  
Old 09-11-2018, 11:21 AM
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dwrichey dwrichey is offline
 
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Forgive me for possibly hijacking this thread, but can someone lead me to information on how to best raise the temperature of just one cylinder approximately 25 degrees? Cylinders 1, 2, and 3 are within 5 degrees of each other (340 -350F) but cylinder 4 is about 25 degrees cooler. Oil temp- 185-190 degs. While number 4 is coolest CHT, it simultaneously is the hottest EGT so I am thinking I don't want to lean it out.
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  #7  
Old 09-11-2018, 12:17 PM
ukncessnadrvr ukncessnadrvr is offline
 
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dwrichy - I have the same CHT spread as you. 1,2,and 3 run 320-340, and #4 is always 25-35 degrees cooler. And #4 has the hottest EGT. O-360 Lycoming. Iím over 1,000 hours and itís always been this way. Leaning doesnít seem to change the relationship.
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  #8  
Old 09-11-2018, 02:35 PM
Adam Adam is offline
 
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I have seen two engines that were supposedly running cool, actual problem was they both had cht senders that did not have a spring forcing the probe to make contact with cylinder so they were just measuring dead air
_


Thanks Jerry Ill check that!
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  #9  
Old 09-11-2018, 03:52 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Iíd first verify the accuracy of your CHT readings. As you have a standard Vanís cowl setup Iíd be suspect.
Seriously, there is nothing suspect about a standard RV-8 cowl. I've seen the pressure measurements.
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  #10  
Old 09-11-2018, 04:08 PM
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AlexPeterson AlexPeterson is offline
 
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Quote:
Originally Posted by Adam View Post
Guys I have an issue that most people donít, my CHTís run very cool this has been going on for many years and for the most part Iíve been pretty proud that I didnít have an issue of high CHTís. About two years ago I had a sticky valve I had taken care of it and the plane has been flying fine. When I was out at Oshkosh this year I met with Superior Engines and spoke with them for quite a while I told them of my issue with my low temps and their concern was thatís why Iím having a sticky valve as most of my temperatures never get above 300į in Normal straight level flight. Typical temperatures range from about 265į to about 295į cylinders 1 through 4, running 25 square at 4000 feet lean of peak at 78į outside temperature. So my question is what should I do, do, I close up the intake or do I close off the exit part of the cowling. Just a few bits of information this is an RV-8 with an I/O 360 fuel injected with a standard cowl the only thing that is different is I have an exhaust system that is 4 into 1.
What fuel burn is this? How much LOP are you running? (perhaps for a separate discussion, LOP is usually not recommended above about a 24/2400 setting). Mixture has a powerful effect on CHT. I can run mine anywhere from 375 down to 300 depending on mixture.
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