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  #11  
Old 08-16-2019, 04:37 PM
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scottmillhouse scottmillhouse is offline
 
Join Date: Apr 2007
Location: Madison, AL
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Looking through all my Savvy Analysis data I see that I have not had a notable cylinder head temperature drop yet. Actually the first two hours at 75%+ full rich circling the airport is looking cooler than my recent XC flights, closer to 400. Lycoming did get heads up to 440 in their test cell during their full power run portion. I've noted the lower baffle mods to provide customized flow to address a hot cylinder for future consideration. I'll probably spend time on that later but for now I just want to lower my CHTs across the board so that I'm comfortable continuing Phase I testing with slow flight, climb performance and pattern work. I'll check and then try retarding the timing to get heat down so I can run the engine harder without fear of redline CHTs.
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Last edited by scottmillhouse : 08-17-2019 at 03:24 PM. Reason: Edit
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  #12  
Old 08-17-2019, 03:27 PM
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scottmillhouse scottmillhouse is offline
 
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The VAF brain trust did it again. Left mag about 29 degrees with right at 25. Changed to 24. Hopefully that is the issue. I don?t know if Lycoming set it wrong or if it drifted in last 10 hours. Next flight will see if it is fixed.
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  #13  
Old 08-20-2019, 04:25 PM
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scottmillhouse scottmillhouse is offline
 
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Timing was the problem. Temperatures in 360-380 range now and peaks at 400-410 on take off but OAT was almost 90 here for take offs and 80 at altitude. All CHT are within 10 degrees now.
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  #14  
Old 08-20-2019, 06:46 PM
49clipper 49clipper is offline
 
Join Date: Dec 2006
Location: Belleville
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Default 49clipper

You know the timing will drift as the points wear. And it will advance. There is also an AD out on that if the drift occurs within 5 hours of timing. Just for you reference.
Jim
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  #15  
Old 08-20-2019, 07:07 PM
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bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
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Default A little goes a long way...

I have a YIO-360-A1B6 with dual Lightspeed Plasma III's.

I researched the old Lycoming SI/SB from the 1970's and I pondered the whole 25? vs 20? thing, 8.5:1 vs 8.7:1 CR and the odd -A1B6D variant that uses 25? -- I convinced Klaus to make me a 22? magnet ring for use with his system and I happily flew off my 40 hours.

What struck me was how hot things were when compared with my last engine (also an IO-360-A1B6). CHT's hit 400?F during initial break in and settled at ~380?F using best power fuel flows.

I recently had the opportunity to remove the prop (needed to be resealed -- another story) and I decided to go with "stock" timing -- I installed the 20? magnet ring. What a difference 2? in timing made! CHT's dropped by > ~20+? and lean of peak fuel burn also dropped almost 1 GPH.

Net-Net - Timing makes a difference...Check it, even if it's New In the Box from Lyco...
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  #16  
Old 08-20-2019, 07:26 PM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by scottmillhouse View Post
Timing was the problem. Temperatures in 360-380 range now and peaks at 400-410 on take off but OAT was almost 90 here for take offs and 80 at altitude. All CHT are within 10 degrees now.
Glad you got this figured out, 360-380 is a very good number of your engine specially in the warmer weather.

The mods for the baffles are also a good advise but it is more work specially now that they have installed. Why mess with it if you have good temp.

Good luck with your phase I
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  #17  
Old 08-21-2019, 09:41 AM
WingsOnWheels WingsOnWheels is offline
 
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I am having similar high CHT issues right now on my O-360. I am 15 hrs into phase 1. The engine wasn't new, but the top-end was fresh. I have a plenum and have resealed that thing multiple times. At this point, I think it would hold water upside down...haha. I retarded the ignition 2 degrees as well to 23 (to go father I have to shift a tooth on the mags). Right now the engine only gets below 400 on decent or low-power even running well below peak EGT. Pretty much all operations are over 400. I have to climb out at 110+ to stay under 450. The thing is hot. Oil temps aren't bad, they peak at 215 or less after climb out. The engine doesn't really use any oil.

I am running out of ideas at this point. I am going to mess with the inlet connection from the plenum to cowl a little more, but I don't see much opportunity there.

I do have the vetterman 1.5" system with mufflers. I wonder if the possible additional restriction is causing problems.
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  #18  
Old 08-21-2019, 10:46 AM
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DanH DanH is online now
 
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Colin, remember a plenum is a sealing device, nothing more. Sounds like you've made sure it seals well, which is good.

There are other requirements for good cooling. You need good conversion of available dynamic pressure to increased static pressure above the engine. Although there are several contributors, it is mostly a function of inlet design. Good systems raise static by 0.8 x available dynamic pressure or more. In one set of pressure measurements, a certain popular cowl/plenum combination only came in at about 0.65.

Next you want all the air to pass between the hot parts for as far as possible. The big sin in this regard is aluminum baffle wraps which do not tightly conform to the tips of the fins. It allows air to flow out the sides of the wraps, rather than continuing between the fins all the way to an exit near the lower spark plug.

The intercylinder baffle plate should be silicone sealed to the case, etc.

It's common to find a major leak at the base of cylinders 3 and 4, aft side, where a tab on the rear baffle wall should have been bent to close the gap.
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Last edited by DanH : 08-21-2019 at 10:48 AM.
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  #19  
Old 08-21-2019, 10:51 AM
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Carl Froehlich Carl Froehlich is offline
 
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Collin,

Something is not right.

You might want to mention your fuel flows. I?m no carburetor expert but I would verify the engine is getting enough fuel when ROP.

Carl
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  #20  
Old 08-21-2019, 04:00 PM
WingsOnWheels WingsOnWheels is offline
 
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Location: Plano, TX
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Dan,

Thank you for the advice. I checked out the inter-cyl baffle before, but I will take another look. When I fitted the baffles, I carefully bent the wraps to ensure they matched the cyl contour, i don't have any gaps that I could find, but will look again. I will take a close look at the rear tab of 3/4 as well. I have an older engine, so I do not have the casting line across the back of 3 snd front of 1, so I have not done the cutout mod to the baffles there.

Do you happen to have a good picture of a properly sealed inter- cylinder baffle I could see for reference?

Carl,
My fuel flow is in-line. 14+gph in climb. I can get a good 200+ egt rise when I lean at cruise.

Thanks,
Colin
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