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  #11  
Old 09-12-2018, 11:18 AM
dwrichey's Avatar
dwrichey dwrichey is offline
 
Join Date: May 2009
Location: Reedley, California
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Quote:
Originally Posted by Adam View Post
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!
Also thank you Jerry, I will check that out also, but I am not too optimistic because the plugs in cylinder 4 are always black compared to the other three cylinders. I'm thinking I can wrap the cylinders from the top in such a way (fiberglass cloth held in place/saturated with RTV) that will bring the one cylinder temperature up. I believe the F1 guys at Reno do something similar to improve cooling efficiency, I would just need to neck the opening down a little more.
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  #12  
Old 09-12-2018, 11:44 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 4,413
Default Whoa . . hold on a minute

Quote:
Originally Posted by dwrichey View Post
Also thank you Jerry, I will check that out also, but I am not too optimistic because the plugs in cylinder 4 are always black compared to the other three cylinders. I'm thinking I can wrap the cylinders from the top in such a way (fiberglass cloth held in place/saturated with RTV) that will bring the one cylinder temperature up. I believe the F1 guys at Reno do something similar to improve cooling efficiency, I would just need to neck the opening down a little more.
I have my barrels (M1B 180 hp) wrapped to a 3" opening at the top, and unwrapped the 2 & 4 barrels to 5 " and there was zero change in the CHT balances. It is helpful to wrap up to the centerline though just for air volume management. I think wraps will affect piston temps more than anything else. Nothing we currently measure.

For CHT I would suggest review of the opening gaps under the head and barrels first, closing them slightly. Edit: My gaps are the James recommended (and others) 1" lower gap and 2.25 for the heads. Then, consider wrapping on the top of the fins. Use some aluminum tape first. Might be easier to just do two heads first to compare the balance - rather than all 4 and attempt evaluation using a flight to flight differences. Too many variables.

Kinda hard to understand your low CHT's with a parallel valve engine. Easier to fix than too hot.
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Last edited by BillL : 09-12-2018 at 11:59 AM.
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  #13  
Old 09-13-2018, 10:28 AM
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db1yg db1yg is offline
 
Join Date: Mar 2006
Posts: 611
Default Wrong Sensors

Hey Adam,

I would like to relay a story that might be of interest to you.

Last year a friend purchased a flying RV7a/360/FP Sens Propeller aircraft. Just before purchase the prior owner had dual HDX Dynons installed. The plane had stock baffles and stock Vans cowl.

The plane was delivered to my friend and after the transaction the data from the Dynon data log was down loaded. It showed that the cht's were running in the mid 250's f on the delivery flight in warm temps and high power/rpm settings. By this time we had seen the baffles (multiple leaks) and we were pretty sure that the temps were not as they were logged. Turns out the prior owner had kept some old sensors and spliced them to the new Dynon wiring---they were a mismatch. The sensors were replaced with a set made for the HDX and all is now normal with temp usually in the mid 300's. If you purchased this plane flying, is it possible that you also have mismatched probes? An easy way to test is to buy one probe that matches your engine monitor and see if the temp for that cylinder changes significantly.

If you built the plane and have matching probes trash this post.

Cheers,

db
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  #14  
Old 09-13-2018, 03:01 PM
49clipper 49clipper is offline
 
Join Date: Dec 2006
Location: Belleville
Posts: 276
Default 49clipper

Don't worry about it. Mine has run at those exact temps for 10 years now. I called Lycoming twice about it, and their response was, You are a very lucky guy and your engine and cylinders will outlast you. Call me back when they get down into the 100-200f range". no issue at all. My probes have been replaced and checked several times. they are perfect (if there is such a thing as perfect).
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  #15  
Old 09-13-2018, 03:15 PM
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ColoRv ColoRv is offline
 
Join Date: Apr 2012
Location: Tampa (BKV)
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My angle valve runs cool too. 300ish in high speed cruise. I have tightly sealed baffles with a tight fit plenum lid. It just cools really well. I intend to close off some exit space at some point, see if I can get these temps up to at least mid 300ís in cruise and reduced e cooling drag at the same time. If that works, Iím contemplating a few ideas for adjustable exit volume.
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