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  #21  
Old 07-16-2017, 02:13 PM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by jrs14855 View Post
I pay a lot of attention to what Mahlon Russell says and not so much to others. I do not have access to my notes but my recollection is that Mahlon recommends an absolute maximum of 425 CHT until you are CERTAIN the rings have seated. Anything higher and you are in an area where glazing the cylinder walls is likely.
Pulling the throttle back for a minute of two on initial climb is FAR BETTER than glazing the cylinders.
With the 0 320 at 6000' PRESSURE ALTITUDE 21" mp and 2650 r/m I was still at 75% according to the Lycoming power chart.
If you are close to full throttle and below 5k pressure altitude you should be fine. How many total hours??
Total hours are now at 6 1/2 actual airborne time. The trouble is that I live at 5000 ft DA even early in the morning in the monsoon season.

When the CHTs show 410 red on the Skyview at less than 500 ft AGL during climb out I'm a little wary of pulling back the throttle.
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Last edited by az_gila : 07-16-2017 at 02:16 PM.
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  #22  
Old 07-16-2017, 02:36 PM
jrs14855 jrs14855 is offline
 
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Default Break In

At Havasu I was a bit better off on DA but not by much. I had to pull the power back below 500' to control the CHT. At 130 kts IAS I could go back to full throttle. My afternoon flights were with temps in the 120 range.
The Tailwind weighs 925 empty and I would typically have 25 gal fuel. I think the Tailwind accelerates better and goes quite a bit faster than the RV6. Also I had gear fairings for the initial flights and wheel pants very early in testing. My wheel pants added 8 kts.
I have considerably less cowl inlet and outlet than a typical RV. I also have a plenum which seems to work extremely well.
I have the cooler behind #3 and the single CHT is on 3. 360-380 CHT in cruise in hot weather. Oil gets too cold below 60 degrees ambient.
Again 10-1 pistons which most of the experts say will cause cooling problems. That has not been the case for me.
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  #23  
Old 07-16-2017, 02:42 PM
jrs14855 jrs14855 is offline
 
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Default Break In

Forgot to mention I now have a Whirlwind GA prop which is a huge improvement over the previous Sterba which had way too much pitch. I am extremely happy so far with the Whirlwind. Cruise has not changed much but takeoff and climb are improved dramatically.
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  #24  
Old 07-16-2017, 05:15 PM
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Ironflight Ironflight is offline
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Gil,

With oil consumption that low, I'd say that you are probably broken in - especially since it got a test stand run-in for 1.5 hours, as you stated. When I was at Lycoming school, they indicated as much.

One of the reasons that you are seeing higher CHT's is because you aren't stuffing enough air (cooling) molecules through the cowling because you don't have the pants on. Adding 12 knots will give you measurably better cooling. Leaving them off does not make the engine "work harder" - it generates power based on throttle setting and prop pitch, and will go as fast as it can at full throttle - and if you make it go slower with more drag, you have lowered the cooling airflow, which is not good.

If you can find Mahlon's instructions, they are basically "run it hard until CHT's drop and oil temp stabilizes", and since it could very well have broken in during the test-stand run-in, you won't actually see either of those. A fresh engine (running but not broken in) might use half a quart an hour until it drops to very small amounts.

And remember that you can get much lower CHT's with LOP operations. I have climbed out of Casa Grande this time of year back when we flew between Houston and Big Bear a lot, and it was always a challenge to keep things cool - we'd climb shallow to keep the speed up to keep oil temps down, and go LOP as soon as power was below 75% to keep CHT's reasonable.

Paul
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  #25  
Old 07-17-2017, 12:38 AM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by Ironflight View Post
Gil,

With oil consumption that low, I'd say that you are probably broken in - especially since it got a test stand run-in for 1.5 hours, as you stated. When I was at Lycoming school, they indicated as much.

One of the reasons that you are seeing higher CHT's is because you aren't stuffing enough air (cooling) molecules through the cowling because you don't have the pants on. Adding 12 knots will give you measurably better cooling. Leaving them off does not make the engine "work harder" - it generates power based on throttle setting and prop pitch, and will go as fast as it can at full throttle - and if you make it go slower with more drag, you have lowered the cooling airflow, which is not good.

If you can find Mahlon's instructions, they are basically "run it hard until CHT's drop and oil temp stabilizes", and since it could very well have broken in during the test-stand run-in, you won't actually see either of those. A fresh engine (running but not broken in) might use half a quart an hour until it drops to very small amounts.

And remember that you can get much lower CHT's with LOP operations. I have climbed out of Casa Grande this time of year back when we flew between Houston and Big Bear a lot, and it was always a challenge to keep things cool - we'd climb shallow to keep the speed up to keep oil temps down, and go LOP as soon as power was below 75% to keep CHT's reasonable.

Paul
Thanks Paul... it's nice to get some details, and it says my engine is probably already broken in

The wheel pants on or off has always confused me a bit, especially when Vans Flight Test section in the instructions specifically mentions flying pantless with new engines. Opinion seems divided when I ask others.

I like your logic on cooling, and Mondays breakfast for 3 local newly made RV-6A's has been monsoon postponed - so an oil change and pant fitting will occur before the next test flight. I'll also repeat a compression test and timing check.

I'll report the flight test results later in the week....
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Last edited by az_gila : 07-17-2017 at 12:40 AM.
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  #26  
Old 07-17-2017, 04:32 AM
mahlon_r mahlon_r is offline
 
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1/4 quart oil consumption in 6 hours = 1quart in 24 or less. It's broken in! No worries about glazing. 425F in the climb is Ok now and as Paul says it will get better as time goes by and the aircraft is cleaned up.
Good Luck,
Mahlon
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  #27  
Old 07-17-2017, 05:48 AM
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Quote:
Originally Posted by az_gila View Post
The wheel pants on or off has always confused me a bit, especially when Vans Flight Test section in the instructions specifically mentions flying pantless with new engines. Opinion seems divided when I ask others.
I also don't get that. The goal is to run the engine fairly hard and keep it cool. You don't have to run it any harder with wheel pants off than with them on, but having them on speeds things up and should help with cooling. Seems counterintuitive. The main reason I see to leave pants off during testing is to be able to keep a good eye on the wheels, tires and brakes while everything is new.
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  #28  
Old 07-17-2017, 12:32 PM
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My #4 cylinder was running 10-15 degrees hotter than the others and routinely >400F in cruise unless managed with faster speed, less power or more fuel. Once I installed the gear fairings and gained ~20 Kts, the engine is much easier to keep cool even in the hotter summer temps.
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  #29  
Old 07-17-2017, 01:06 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by mahlon_r View Post
1/4 quart oil consumption in 6 hours = 1quart in 24 or less.
k,
Mahlon
I think he wrote '1/4 inch' on the dipstick, not 1/4 quart.
What's missing is the fuel flow information. How far (in EGT degrees) rich of peak are you running?
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  #30  
Old 07-17-2017, 01:07 PM
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az_gila az_gila is offline
 
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Quote:
Originally Posted by Jesse View Post
I also don't get that. The goal is to run the engine fairly hard and keep it cool. You don't have to run it any harder with wheel pants off than with them on, but having them on speeds things up and should help with cooling. Seems counterintuitive. The main reason I see to leave pants off during testing is to be able to keep a good eye on the wheels, tires and brakes while everything is new.
Maybe the Vans Flight test instructions are based on cooler, near sea level weather in Oregon, and things can diverge greatly when testing is performed at higher altitude and warmer weather areas of the country?

Right now, I'm 20 F hotter than Portland and 3000 ft higher, and it's a cooler than expected day after thunderstorms during the night.
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