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  #21  
Old 02-24-2016, 10:21 PM
aerhed aerhed is offline
 
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I agree with Kurt.
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  #22  
Old 02-25-2016, 06:20 AM
bluebrear bluebrear is offline
 
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The guy is already a stick. We'll have to deal with him some other way. I can only say thank you to all that offered their help to solve this troubling and perhaps damaging problem. We now have abundant experienced information to apply for a fix.
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  #23  
Old 02-25-2016, 06:33 AM
bluebrear bluebrear is offline
 
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EGT's at high temp were: 1498, 1487,1449 and 1377. At cruise: 1411,1409, 1385 and 1249.
Accordingly, this seems to indicate a carb jet too lean situation. We'll work on it. Thanks
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  #24  
Old 02-25-2016, 07:15 AM
9erDriver 9erDriver is offline
 
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Location: Brookings, SD
Posts: 101
Default connectors in the circuit?

Just throwing this out - CHT thermocouple wires transmit very small voltages, so its best to minimize the use of non-thermocouple connectors and non-thermocouple wiring between the probes and the guage. I did have a similar problem with CHTs reading around 30 degrees too hot, and rewiring the thermocouple wires in a 'direct to' fashion fixed it.
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  #25  
Old 02-25-2016, 08:10 AM
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DanH DanH is online now
 
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The only EGT indication that matters is degrees from peak. Absolute values ("EGT's at high temp were: 1498, 1487,1449 and 1377") are useless for tuning, and only approximate for quickly setting inflight mixture.

Jetting very rich (or very lean) does reduce CHT, but the engine is no longer making rated power. I won't say it's a wrong approach, but it does burn cubic dollars for less whoopee. I'd suggest jetting (or swapping restrictors, or pushing buttons on the SDS control head) so all cylinders fall into the 100 to 200 ROP window, and then working out the necessary cooling to enable the use of all the expensive Lycoming power.

IO-540K angle valve, on the FAA dyno at Hughes. Best power is 100 ROP. Anywhere from 50 ROP to roughly 200 ROP keeps power within 2% of maximum. At 300 ROP power is down about 5.5%.

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Last edited by DanH : 02-25-2016 at 05:58 PM.
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  #26  
Old 02-25-2016, 09:44 AM
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erich weaver erich weaver is offline
 
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Location: santa barbara, CA
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Nice plot. I was confused by it at first until I realized richer is to the left and leaner is to the right along the x-axis.
What am I missing with respect to the purple line at 11:1 F/A and the associated calculation of being 215 degrees ROP? Anything special about that point?

thanks
erich
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  #27  
Old 02-25-2016, 10:18 AM
edbooth edbooth is offline
 
Join Date: Feb 2006
Location: Trenton, SC
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Quote:
Originally Posted by bluebrear View Post
The guy is already a stick. We'll have to deal with him some other way. I can only say thank you to all that offered their help to solve this troubling and perhaps damaging problem. We now have abundant experienced information to apply for a fix.
Just thinking from a different angle, have you checked the routing of your thermocouple leads ? If they are anywhere near higher current flow wires i.e. Alternator, strobe wiring, lights, etc, it's possible your readings could be off and reading high by a significant amount.
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  #28  
Old 02-25-2016, 11:26 AM
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DanH DanH is online now
 
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Quote:
Originally Posted by erich weaver View Post
What am I missing with respect to the purple line at 11:1 F/A and the associated calculation of being 215 degrees ROP? Anything special about that point?
Nope, just an artifact of some previous post. Too lazy to scan a new image
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  #29  
Old 02-25-2016, 11:56 AM
bluebrear bluebrear is offline
 
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Vern, Speaking with Marvel-Shleber, I found out that my carb has one of the richest jets installed. It starts out at .101" dia. Do you have any idea how much increase in the bore would be to attain?
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  #30  
Old 02-25-2016, 01:42 PM
BenNabors BenNabors is offline
 
Join Date: Mar 2014
Location: Alabama
Posts: 127
Talking 11:1 F/A

Big difference between 11:1 F/A and 11:1 A/F!
Takes a while to interpret this chart correctly the first time. As always, another great chart from Dan. I would like to see his reading list over the years.


Quote:
Originally Posted by erich weaver View Post
Nice plot. I was confused by it at first until I realized richer is to the left and leaner is to the right along the x-axis.
What am I missing with respect to the purple line at 11:1 F/A and the associated calculation of being 215 degrees ROP? Anything special about that point?

thanks
erich
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