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  #1  
Old 03-28-2019, 01:06 AM
Jordan1976 Jordan1976 is offline
 
Join Date: Apr 2007
Location: WA
Posts: 159
Default Help: One high EGT

Background: Superior IO-360. 1500 TTSN. Cyl 3 replaced 25 hours ago. Standard slick mags, R&R'd for SB about 10 hours before flight.

Flew outbound for lunch. All EGT's normal, balanced within 20 degrees. Landed, had lunch. Normal run up.Took off, and on climb out, EGT 3 is immediatley 150 degrees higher. When I lean out, all EGTs go into red. CHT's normal or even slightly low. Do some troubleshooting- will barley run on right mag. Continue 15 minutes back to home airport. Find that right mag has slipped timing and is at TDC instead of 25 BTDC.

The problem:
Re-timed both mags to 25 BTDC
Checked all plugs- fine. Rotated plugs.
Compression check - All cyls fine. Cylinder 3 is 79/80.
Cleaned fuel injectors
Ran engine up- EGT's equal until about 100HP / 1250°F. Cyl 3 then quickly goes to 150°F higher
Leaned engine out- all EGT's peak at same time. Assume AFR's are the same

What could lead to EGT 3 being higher only at higher powers? As far as I can tell, the AFR is right, and the compression is fine.
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  #2  
Old 03-28-2019, 05:53 AM
PCHunt PCHunt is offline
 
Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,597
Default

Since the issue is on the newly-replaced cylinder, maybe the EGT probe or wiring?

My first thought was a partially clogged injector, but you state you cleaned them. Debris still in the system and a subsequent clog on #3??

Can you upload any data to Savvy Analysis?
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Last edited by PCHunt : 03-28-2019 at 05:59 AM. Reason: Add comment.
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  #3  
Old 03-28-2019, 07:13 AM
blueflyer's Avatar
blueflyer blueflyer is online now
 
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Location: Shreveport, LA
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Quote:
Originally Posted by PCHunt View Post
Since the issue is on the newly-replaced cylinder, maybe the EGT probe or wiring?...….
I agree, I would swap the probe to another cylinder to see if its the probe.
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  #4  
Old 03-28-2019, 08:44 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 4,330
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In the condition that you find the 150 higher reading, you need to determine what peak EGT is. If the high EGT is above peak temp for the other cylinders, your issue is not fuel/mixture related. The two most common reasons for EGT readings above normal peak are retarded ignition (ignition will be retarded if only one plug is firing in a cylinder) or leakage past the exhaust valve.

Your post implies possible issues with one of your mags, so would start there.

Larry
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Last edited by lr172 : 03-28-2019 at 08:48 AM.
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  #5  
Old 03-28-2019, 02:12 PM
Jordan1976 Jordan1976 is offline
 
Join Date: Apr 2007
Location: WA
Posts: 159
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Thanks everyone.

I feel like I ruled out air-fuel issues. All cylinders still peak at the same mixture setting, EGT just peaks 150°F higher than the others when it used to be the same. It doesn't appear to be running leaner unless I'm missing something.

To be clear- this cylinder was replaced, and between then and now the EGT's have been similar to other cylinders.

I'll replace the EGT probe and see if that fixes it. I actually replaced it when I replaced the cylinder, so maybe this is infant mortality.
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  #6  
Old 03-28-2019, 05:05 PM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by Jordan1976 View Post
Thanks everyone.

I feel like I ruled out air-fuel issues. All cylinders still peak at the same mixture setting, EGT just peaks 150°F higher than the others when it used to be the same. It doesn't appear to be running leaner unless I'm missing something.

To be clear- this cylinder was replaced, and between then and now the EGT's have been similar to other cylinders.

I'll replace the EGT probe and see if that fixes it. I actually replaced it when I replaced the cylinder, so maybe this is infant mortality.
If you see it peaking with the others, just at a higher temp, I would highly suspect the thermocouple or it's wiring.

If that checks out and is not the problem, another possibility is too long of a pushrod. Did you or someone confirm the pushrod size when the new cylinder was installed? Dry lash. Not likely given that it didn't present in the first 25 hours, but something to look at.

Larry
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Last edited by lr172 : 03-28-2019 at 05:10 PM.
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  #7  
Old 03-28-2019, 06:24 PM
jakej jakej is offline
 
Join Date: Aug 2005
Location: Adelaide, Australia
Posts: 115
Default EGT high

Check that RH timing again, if it’s ‘slipped’ then you have an issue with the mag - I have seen that happen on one mag in the past, took several attempts to finally figure it out.
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  #8  
Old 03-28-2019, 06:30 PM
Latech15 Latech15 is offline
 
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Location: louisiana
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I’ve replaced all of the spade type connectors on the egt sensors with the thermocouples that were posted here a while back. All those problems have gone away.
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  #9  
Old 04-07-2019, 09:40 PM
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sglynn sglynn is offline
 
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Location: Anacortes, WA
Posts: 798
Default one high egt

Have you determined the issue with your one high egt temp? I have the same problem. Brand new IO360-M1B. Runs fine. Tach Time is only 5 hours. Still doing break in. Mag checks reveal nothing. At idle all looks good. CHTs move together in the 360's. Cylinders 1, 2, 4 EGTs move together. But on climb out and high power settings #3 egt stands above the other egts by 200 - 300F. Maxing about 1500F.

I've checked and swapped plugs. i detected a little oil on plugs. I'm about to swap probes with another cylinder. But I doubt its bad. Its new. I just read a story about an oval cylinder leaking oil into combustion that increased egt. I hope I don't have that. Are there other tests I can perform to zero in on possible cause?
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  #10  
Old 04-07-2019, 10:48 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by sglynn View Post
Have you determined the issue with your one high egt temp? I have the same problem. Brand new IO360-M1B. Runs fine. Tach Time is only 5 hours. Still doing break in. Mag checks reveal nothing. At idle all looks good. CHTs move together in the 360's. Cylinders 1, 2, 4 EGTs move together. But on climb out and high power settings #3 egt stands above the other egts by 200 - 300F. Maxing about 1500F.

I've checked and swapped plugs. i detected a little oil on plugs. I'm about to swap probes with another cylinder. But I doubt its bad. Its new. I just read a story about an oval cylinder leaking oil into combustion that increased egt. I hope I don't have that. Are there other tests I can perform to zero in on possible cause?
The most common cause of oily plugs on a new engine is glazing, which is most likely to happen in the first hour or two. Traces of oil can be common during the first 5- hours, as the rings fully seat and is not indicative of a problem assuming it goes away by 10 hours. That would not, however, cause high EGT readings. Oil in the cylinder has a very small affect, if any, on EGT. A partially blocked injector could cause the high EGT if you are running 200* + ROP. I am guessing you are running full rich, which should be at least this ROP. This would not cause oily plugs though. A plugged injector is much more likely to appear shortly after work is done on the fuel injection system, including initial installatoin. For a quick test, lean the mixture up a bit. If 1,2,4 all rise and 3 rises just a bit, then drops or just drops, then #4 is running around peak instead of 250 ROP, like the others, and a clogged injector is the most likely cause. I would expect your cyl's to peak around 1500 in high power settings and I would expect them around 1250 or less at full rich.

Larry
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Last edited by lr172 : 04-07-2019 at 11:09 PM.
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