REFLECTOR: CHT's

Tue Oct 20 08:29:03 CDT 2009

1 inch wider??  Thats better than 10% more air I would guess.

Scott

Rene Dugas wrote:
> IO-540 260 hp
> Rene'
> My NACA's are 1 inch wider than recommended by the factory 9 years ago.  
> Second plenum.  First exploded when I started the engine without the plenum
> bolted down and caught in prop.  Not a piece was bigger than 4 x 4 inches. I
> have the slip joint half way up rails with about 1/8th inch opening.  No
> seal has ever been needed.
> RD
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Scott Derrick
> Sent: Monday, October 19, 2009 2:25 PM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: CHT's
>
> Rene, what engine are you running? 
>
> here's an early picture of my plenum.
>
> http://tnstaafl.net/canards/img134.jpg
>
> it was from the factory for a 550, close enough for a 520.  The attachment
> has changed but the overall shape is identical.
>
> Scott
>
> Rene Dugas wrote:
>   
>> I don't know what your naca to plenum looks like but mine is attached 
>> and no diverter was needed.  All my CHT's are within 20 degrees.
>> Hope it helps somehow.
>> Rene'
>>
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
>> On Behalf Of Scott Derrick
>> Sent: Sunday, October 18, 2009 3:10 PM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: REFLECTOR: CHT's
>>
>> Flew this morning after plugging holes in the TCM/Cessna supplied 
>> "between cylinder baffles".  I should have made my own, because the 
>> stock baffles have huge holes in them.  They also don't wrap up around 
>> the sides of the cylinders for optimal cooling flow. I may try to 
>> tighten things up a bit more but it will require me to remove all the 
>> injection plumbing, spark plug wiring and some other stuff..
>>
>> Also adjusted the fuel map and smoothed out a few bumps in the oil 
>> cooler exit duct.
>>
>> The CHT's are really coming into a comfortable range.  Cruising at 165 
>> KTAS(low power setting) they all stay below 360, but increasing power 
>> to above 200 KTAS and  #2  climbed to 395, #1was about 365, the rest 
>> were all below 330.  I'm mostly concerned with #2 but would like to 
>> see
>> #1 more inline with the other 4 as well.
>>
>> I'm debating installing some kind of diverter(s) inside the plenum to 
>> direct more air onto #1 & #2.  Anybody do that to lower CHT's with 
>> success?  How did you do it?  Got pictures? Controlling air movement 
>> is such a funny thing, sometimes what seems logical or intuitive is 
>> exactly the wrong thing to do!
>>
>> The fuel map is as good as I will be able to get it, until I get the 
>> new prop.  At least I am not running at peak EGT in RPMs above 2200 now.
>> That helped the temps a whole lot.
>>
>> Now to getting the oil temp down some more. Right now I am not running 
>> the fan on the secondary cooler as I see it as a summer time auxiliary
>>     
> cooler.
>   
>> With OAT in the 60's I shouldn't need it.  The oil temps were OK, but 
>> a bit on the high side at a low power cruise speed of 165KTAS.
>> about 210F, but as soon as I fire-walled the throttle it started to 
>> come up and seemed to stabilize at around 230, though I didn't stay at 
>> that power setting more than a couple of minutes.  With the IO360 my 
>> current oil cooler was good enough but marginal.  On hot days I had to 
>> step climb.  I don't have an exit scoop or air dam on the exit duct.
>> The duct opening is flush with the fuselage. I'm really intrigued with 
>> Don's idea of an Oil cooler flap that can be adjusted from the 
>> cockpit. When flying with the IO360 I had too much cooling in the 
>> winter and marginal in the summer. I would tape some of the cooler 
>> face in the winter so my temps were hot enough to get a bit of warm 
>> air in the cabin.  With a hinged controllable flap I could set it for 
>> whatever the conditions were.  It would probably work out to 3 or 4
>>     
> settings that covered all scenarios.
>   
>> Scott
>>
>>
>>
>>
>>
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