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Has anyone experienced higher takeoff CHTs after LASAR Cowl?


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When I put the LAsar Cowl on my 68c with fixed Cowl flaps I immediately noticed higher takeoff CHTs. I rarely ever broke 400 on any cylinder according to the JPI before, no matter what i did, and I normally did short field takeoffs. Now, I routinely will go a little over 400 while working to keep temps down, both by not using short field technique, and by reducing power much earlier then I did before.

 

Cruise temps do seem to be noticeably down.

 

When I put the LASAR cowl on I also sealed up the doghouse baffling much better then it had been before. I sealed around the areas where the engine mounts pass through the baffling. And using a flashlight, I put foil tape everywhere I could see light coming through while looking through the cowl inlet.

 

Is it possible that the new "inlet to fixed flap ratio" just isn't optimal for takeoff? If so, then I shouldn't be the first to experience this. I'm wondering what others with fixed flaps think about this? As an experiment, I left off the foil tape recently when I had the doghouse cover off ( which leaves a thin air gap all around the top cover the thickness of the tinnermen nuts), flying today it seemed to make no change, so I'm inclined to blame the higher takeoff temps on the cowl mod. Anyone have any thoughts on this?

 

 

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Unless you're trying to clear trees, you're better off not using any sort of short field technique once you climb above a hundred feet or so.  120 mph will give about the same rate of climb as 95, albeit at a much worse angle- but your CHTs will be much cooler.

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I routinely climb at Vy (100 mph - altitude) without CHT problems except sometimes in the summer. I do have the guppy mouth closure. Resurrecting my doghouse improved my cruise speed 10-12 mph, but I didn't notice much effect on CHT. 

Then again, I also leave all three levers full forward; when I remember, I lean to Target EGT. There is no "power reduction" until after I level off and accelerate, and then it's just to set cruise power and lean.

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12 hours ago, N9495V said:

Check the  "December 2016 M20C (fixed) cowl flaps opening" thread and you will find a series of pictures showing the cowl opening of M20c's with fixed cowl flaps. Your cowl flaps opening is significantly larger than most of the fleet.   

Wow, that's interesting. 

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21 hours ago, N9495V said:

Check the  "December 2016 M20C (fixed) cowl flaps opening" thread and you will find a series of pictures showing the cowl opening of M20c's with fixed cowl flaps. Your cowl flaps opening is significantly larger than most of the fleet.   

Weird, I was thinking his cowl flap opening looked small compared to my old 20C...

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