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  #1  
Old 11-21-2017, 08:33 AM
Sdemeyer Sdemeyer is offline
 
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Location: Olympia,wa
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Default EGT and CHT at WOT

Not sure if this is a problem but its not something I have experienced yet. At WOT on takeoff, my #2 cylinder egt rapidly climbs to 1560 deg and the CHT also goes up more than the other cylinders. After leveling off and setting cruise power, the temps come down but #2 is always warmer than the other cylinders. I removed the air dams in front of #1 and #2, checked for induction leak, borescoped #2 cylinder but do not see anything out of the ordinary. Fuel flow seems adequate and engine is very smooth running. Any ideas? The engine is an O320 150HP and has about 15 hours SMOH on an RV6A

Takeoff and climbout WOT
egt1 by scottsr1100rt, on Flickr

Cruise power
egt2 by scottsr1100rt, on Flickr
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  #2  
Old 11-21-2017, 08:47 AM
vic syracuse vic syracuse is offline
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Fuel flow does seem OK for an O-320. Have you checked the ignition systems at that high power setting? A bad plug will cause higher EGT's. I'm assuming it is carburated.
You mentioned recently overhauled? Carb, too?

Vic
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  #3  
Old 11-21-2017, 08:48 AM
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Toobuilder Toobuilder is offline
 
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When you lean, does #2 peak way before the others or is it within the normal spread? If this was an injected engine, I'd say you had a partially blocked #2 injector, but with a carb, you have an induction leak or a plug problem.
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  #4  
Old 11-21-2017, 02:28 PM
Sdemeyer Sdemeyer is offline
 
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I have not done a full power ignition test but the mag drop when done at runup is fine, less than 50 RPM. The carb was purchased from ACS, for this engine and was overhauled so it has the same amount of hours as the engine. I will swap some plugs around and see if the problem follows. Not really sure how or where I could have an induction leak as there is not many places it could leak from and all the connections seem to be OK. I will dig around some more and also check the mag timing to make sure its still where it should be. I have not done much leaning yet as haven't had a chance to climb very high, so not sure if #2 will peak first.
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  #5  
Old 11-21-2017, 02:32 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by Sdemeyer View Post
. I have not done much leaning yet as haven't had a chance to climb very high, so not sure if #2 will peak first.
There is no need to climb high. Set the power at 75% or less, and lean. Note which cylinders hit peak EGT first, second, etc., and by how much difference in fuel flow.
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  #6  
Old 11-21-2017, 02:44 PM
Sdemeyer Sdemeyer is offline
 
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I was reluctant to do much leaning down low because of the already high temps and I really don't want to start melting metal. Next time we have a decent day up here in PNW, I will give it a try.

Quote:
Originally Posted by BobTurner View Post
There is no need to climb high. Set the power at 75% or less, and lean. Note which cylinders hit peak EGT first, second, etc., and by how much difference in fuel flow.
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Last edited by Sdemeyer : 11-21-2017 at 02:58 PM.
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  #7  
Old 11-21-2017, 03:18 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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Not an answer to your issue, but compared to my O-320 150HP, your fuel flow numbers seem high, even for break-in. My cruise fuel-flow at 2000' would be closer to 7 GPM at 65% power, which would be ROP. Don't be afraid of the red knob even down low.

Keep in mind that EGT temps by themselves mean little, and sensor placement can cause some cylinders to read higher than others. And intake leak or ignition problems are certainly possible and worth checking into.

Regarding CHT's, in a carb'ed engine especially, the uneven fuel, air, and cooling in a carb'ed engine means some cylinders will always be slightly hotter than others in different flight regimes. You will find that you can cool the front and heat the rear cylinders by going WOT which tends to result in richer mixtures in the front cylinders, and vice versa. Airflow on different sides (maybe from propeller slipstream?) also affects cooling - it looks like in climb your left cylinders (2 and 4) get much less cooling airflow than 1 and 3. On the plus side, you don't have the hot #3 cylinder that many people struggle with. Your cruise CHT's look pretty normal to me, and will probably come down with break-in. Mine run 340's in the warmer months and were 320's yesterday on a flight from FL to NC. at 13,500.

You don't need to worry about leaning down low - as long you get under 60-65% power you can't hurt it with leaning, and you can monitor temperatures and take action well before anything gets too hot, should that be an issue.

Chris
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Last edited by YellowJacket RV9 : 11-21-2017 at 03:35 PM.
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  #8  
Old 11-21-2017, 07:31 PM
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snopercod snopercod is offline
 
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The position of the throttle butterfly has a major impact on front vs. back EGTs. At WOT my front cylinders run rich and my rear cylinders run lean until I get in the cruise configuration. In cruise, I lean out and then make fine adjustments to the throttle position until the EGTs are almost equal. Does your carb have the "peppermill" nozzle with the aeration holes in the barrel?
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  #9  
Old 11-21-2017, 09:44 PM
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RVbySDI RVbySDI is offline
 
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Quote:
Originally Posted by Sdemeyer View Post
I was reluctant to do much leaning down low because of the already high temps and I really don't want to start melting metal. Next time we have a decent day up here in PNW, I will give it a try.
You can lean sitting on the ground. As Bob said, keeping power below 75% and metal will be just fine. In fact, get too lean and you will notice a couple of things. The EGT will start dropping (not rising) if you go LOP. Go too lean and the engine will die. Not much chance of "melting metal" then. You are not trying to replicate your climb experience. You are just trying to analyze what each cylinder is doing during the process. Watch your temps closely while analyzing performance and your engine should be fine.
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  #10  
Old 11-22-2017, 08:42 AM
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sirlegin sirlegin is offline
 
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On my 0320 engine oil temp should be 120 before takeoff?
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