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09-10-2018, 03:50 PM
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Join Date: Jan 2005
Posts: 269
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Cool CHTs
Guys I have an issue that most people don?t, my CHT?s run very cool this has been going on for many years and for the most part I?ve been pretty proud that I didn?t have an issue of high CHT?s. 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 that?s why I?m having a sticky valve as most of my temperatures never get above 300? in Normal straight level flight. Typical temperatures range from about 265? to about 295? cylinders 1 through 4, running 25 square at 4000 feet lean of peak at 78? 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.
__________________
Adam Silverstein
Technical Counselor Chapter 643
Flying RV-8 10/30/07
PAID 2021
Pittstown, New Jersey
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09-10-2018, 04:27 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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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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Dan Horton
RV-8 SS
Barrett IO-390
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09-10-2018, 05:29 PM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,596
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I?d first verify the accuracy of your CHT readings. As you have a standard Van?s cowl setup I?d be suspect.
Carl
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09-10-2018, 07:16 PM
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Join Date: Jan 2005
Posts: 269
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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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Adam Silverstein
Technical Counselor Chapter 643
Flying RV-8 10/30/07
PAID 2021
Pittstown, New Jersey
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09-11-2018, 09:54 AM
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Join Date: Jan 2009
Location: Chino, CA
Posts: 202
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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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Jerry Scott
Rocket II
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09-11-2018, 11:21 AM
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Join Date: May 2009
Location: Reedley, California
Posts: 85
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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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09-11-2018, 12:17 PM
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Join Date: Mar 2009
Location: Duncanville, TX
Posts: 32
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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. I?m over 1,000 hours and it?s always been this way. Leaning doesn?t seem to change the relationship.
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John Winchester
Sold 172L and bought flying RV-6
Based at GPM
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09-11-2018, 02:35 PM
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Join Date: Jan 2005
Posts: 269
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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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Thanks Jerry Ill check that!
__________________
Adam Silverstein
Technical Counselor Chapter 643
Flying RV-8 10/30/07
PAID 2021
Pittstown, New Jersey
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09-11-2018, 03:52 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Carl Froehlich
I?d first verify the accuracy of your CHT readings. As you have a standard Van?s cowl setup I?d be suspect.
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Seriously, there is nothing suspect about a standard RV-8 cowl. I've seen the pressure measurements.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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09-11-2018, 04:08 PM
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Join Date: Sep 2005
Location: Maple Grove, MN
Posts: 2,333
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Quote:
Originally Posted by Adam
Guys I have an issue that most people don?t, my CHT?s run very cool this has been going on for many years and for the most part I?ve been pretty proud that I didn?t have an issue of high CHT?s. 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 that?s why I?m having a sticky valve as most of my temperatures never get above 300? in Normal straight level flight. Typical temperatures range from about 265? to about 295? cylinders 1 through 4, running 25 square at 4000 feet lean of peak at 78? 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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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.
__________________
Alex Peterson
RV6A N66AP 1700+ hours
KADC, Wadena, MN
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