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  #1  
Old 01-06-2014, 12:44 PM
Adam Adam is offline
 
Join Date: Jan 2005
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Default Low CHT

I'm one of the guys that has a problem with a low CHT. I know many of you have high CHTs and high oil temps put I have the opposite issue. I have a standard Vans cowl with an Superior I0-360,, on days that the temp is say 75 degrees my CHT is usually from 250 to under 300. On cold days my run up temps are higher then my in flight temps. I have checked all my probs and they read correct. My issue is that because the cylinders run so cool I get cokeing of the valve guides. What is the best way of dealing with this?
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  #2  
Old 01-06-2014, 04:41 PM
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RV10inOz RV10inOz is offline
 
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Location: Brisbane Qld. Aust.
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Default

Quote:
Originally Posted by Adam View Post
I'm one of the guys that has a problem with a low CHT. I know many of you have high CHTs and high oil temps put I have the opposite issue. I have a standard Vans cowl with an Superior I0-360,, on days that the temp is say 75 degrees my CHT is usually from 250 to under 300. On cold days my run up temps are higher then my in flight temps. I have checked all my probs and they read correct. My issue is that because the cylinders run so cool I get cokeing of the valve guides. What is the best way of dealing with this?
What makes you think they are too low? Is this a low compression engine? The Superior cylinders do for some reason run cooler, better fins and less flashing etc maybe? DanH might have some wise words on that.

As for cooking of the valves, please qualify what you mean by that. Otherwise it seems fine to me.
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  #3  
Old 01-06-2014, 05:53 PM
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Walt Walt is offline
 
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Oil coking is a high temperture condition (think burnt oil) and generally assoiciated with turbines in my experience. If you are suffering from sticky valves this is generally caused by lead contaminated oil /failure to lean.

Low CHT's are fine (better than high CHT's), your temps are nothing to be concerned with especially in the winter.
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  #4  
Old 01-06-2014, 08:25 PM
Adam Adam is offline
 
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Your right about cokeing that would be a hot oil issue,, the problem is that there is a lead build up on the valve guides that causes a sticky valve and the engine to shutter every so often. I lean all the time and fly lean of peak. My concern is that because the temps are so low the lead dose not get burned off.
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  #5  
Old 01-06-2014, 09:44 PM
crabandy crabandy is offline
 
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I've heard that running LOP allows lead deposits to build up and that You should also run some higher power settings intermittently to help clean off these deposits. I have no facts just word of mouth, perhaps someone else...
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  #6  
Old 01-07-2014, 07:02 AM
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RV10inOz RV10inOz is offline
 
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LOP operations do not cause lead or Lead Oxybromine deposits to be any worse, in fact they are better.

Valve guides could well be an issue from manufacture, and I would suggest that any talk of the contrary is a smoke screen. Otherwise I can show you thousands of engine all stuck up and failing........Nope not happening.

Oil issues maybe....

Walt is right.....
Quote:
your temps are nothing to be concerned with especially in the winter.
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  #7  
Old 01-07-2014, 07:18 AM
brad walton brad walton is offline
 
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Location: Cypress, TX
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Default Too low

I have a Superior IO360 also and your temps seem unusually low to me. I am curious as to why. Efficient cooling is great, but you are running 75 to 100 f cooler than most. Are you confident you are making full power? Confident in your gauges/probes? Running overly rich? There must be something else going on here.
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  #8  
Old 01-07-2014, 07:31 AM
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Walt Walt is offline
 
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As a point of reference my ECI runs around 280-300F during cold weather (cold to me is <50F, I don't usually fly when its less than 40F).
I rarely see anything above 350 even in the Texas summer heat.
The above is typical at my cruise power of 65%
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
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Last edited by Walt : 01-07-2014 at 08:03 AM.
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  #9  
Old 01-07-2014, 07:45 AM
brad walton brad walton is offline
 
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Location: Cypress, TX
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On a 75 f day at 60 percent power, my cht s are about 345 f. The other day at 32 f, my cht s were about 320. If I lop on a 75 f day, I can get down to 300 f at low power setting
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  #10  
Old 01-07-2014, 08:45 AM
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skylor skylor is offline
 
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Location: Southern California
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Default Not Too Low

Quote:
Originally Posted by brad walton View Post
I have a Superior IO360 also and your temps seem unusually low to me. I am curious as to why. Efficient cooling is great, but you are running 75 to 100 f cooler than most. Are you confident you are making full power? Confident in your gauges/probes? Running overly rich? There must be something else going on here.
I have a stock lycoming IO-360 angle valve, and Adam's CHT's are in line with mine. I typically don't see anything over 360 on a hot day/full power extended climb, and my cruise CHT's run between 260-310F. This is with the stock cowling and baffles, except that my oil cooler (stock vans FWF Niagara) is mounted behind #3 instead of #4.

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