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  #11  
Old 01-25-2022, 07:00 AM
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jcarne jcarne is offline
 
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Location: Worland, Wyoming
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Larry, thanks for bringing this back up as I had forgot about it. Here is my take.

I covered the louvers with speed tape and it made about a 5-10 degree increase in temps. While I haven't done an accurate speed test it does seem that my cruise speeds for my typical setting have also gone up about 2 maybe even 3 knots.

My long term thinking is to still put cowl flaps in their place. The louvers absolutely are not needed during the winter or any weather relatively cool. However, hot summer day climbs I can see why Van's put them on. I also don't find they are needed on hot summer cruising.

Also, there seems to be a lot of negativity surrounding cowl flaps. In short, yes the RV does not NEED them but to be honest I don't think the stock setup is optimized for climbs (if it was the speed would be lower at cruise). So a guy has 3 options:

1. accept higher than 400 CHTs on the climb on hot days, especially if you want to climb below 115 knots indicated.
2. go to lengths that Danh does on baffles (it obviously works really well)
3. install cowl flaps, open them during climb and close for the rest of the flight and take a small weight penalty

Timing also matters, if I didn't have a Pmag my CHTs would be insanely low. Pmags are well known to raise CHT 20-30 degrees from a stock setup.

In summary, I have good baffles, not Dan good but pretty dang good, like to climb below 115 KIAS initially, and want to close some area during winter at all times. Sounds like cowl flaps will fit my bill. Hope this helps.
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Last edited by jcarne : 01-25-2022 at 07:03 AM.
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  #12  
Old 01-25-2022, 08:46 AM
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Draker Draker is offline
 
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Sorry I should probably know this but what is the concern about low CHTs? Isnt cooler generally better?
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  #13  
Old 01-25-2022, 09:27 AM
Northernliving Northernliving is offline
 
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Quote:
Originally Posted by Draker View Post
Sorry I should probably know this but what is the concern about low CHTs? Isnt cooler generally better?
I had the same question a while ago so looked it up in the IO-360 Lycoming Operating Manual that states, "For maximum service life of the engine, maintain cylinder head temperature between 150F and 400F during continuous operation." so that's what I'm using as a safe operating range.

https://www.lycoming.com/sites/defau...2060297-12.pdf
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  #14  
Old 01-25-2022, 09:34 AM
A2022 A2022 is offline
 
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Quote:
Originally Posted by Northernliving View Post
I had the same question a while ago so looked it up in the IO-360 Lycoming Operating Manual that states, "For maximum service life of the engine, maintain cylinder head temperature between 150F and 400F during continuous operation." so that's what I'm using as a safe operating range.

https://www.lycoming.com/sites/defau...2060297-12.pdf
when running cold CHT's below 300F I noticed I had some EGT readings that were slow to rise. I could not explain this. after I began using cowl inlet air dams to get the CHT's to be always above 320F or so, the issue went away. now I get a normal response from my EGT's. I don't know why cold CHT's would cause this or if it even was related. it is just my observation.
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  #15  
Old 01-25-2022, 12:14 PM
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wcalvert wcalvert is offline
 
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Steve Your slow EGT response with low CHT's might be indicating reduced efficiency in the fuel burn.... just my theory. Seems like combustion would be optimized at a certain temperature range, maybe you found the bottom end.

Any powerplant engineers out there who could comment?
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  #16  
Old 01-25-2022, 12:25 PM
A2022 A2022 is offline
 
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Originally Posted by wcalvert View Post
Steve Your slow EGT response with low CHT's might be indicating reduced efficiency in the fuel burn.... just my theory. Seems like combustion would be optimized at a certain temperature range, maybe you found the bottom end.

Any powerplant engineers out there who could comment?
slow EGT's were only on one or sometimes two cylinders, but they were consistently slow to come up. I almost pulled a valve rocker to check the valve guide. after getting the CHT's up during the Winter months with cowl air blockage, this issue went away. all EGT's coming up normally. who knows? nothing conclusive.

Last edited by A2022 : 01-26-2022 at 06:29 AM.
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