REFLECTOR: !Re: Oil cooler VG photo
Dave Nelson
davenali at charter.net
Sun Jul 16 21:40:36 CDT 2006
Thanks, Ron. I much appreciate the data point. I assume you have just one
oil cooler mounted in the nose (?).
Looking at your data - what do you see happen if the OAT goes from 71 deg to
say, 85 or 90? I see a fairly linear correlation between OAT and Oil T. As
an example, if the OAT goes up 10 degrees, I see approx. 10 degree increase
in oil temperature.
Also - it's interesting to note that even though your CHTs are very much
under control, your oil is still marginally hotter than the optimum (based
on the Lycoming engine operation manual). This interests me because it
lends credibility to the advice I get from Lycoming engineering - that CHT
and oil temperature must pretty much be managed independently (obviously
within limits). Bottom line, though - I'd trade places with you in an
instant!
Thanks again.
Dave
----- Original Message -----
From: "Ron Brown" <romott at adelphia.net>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Sunday, July 16, 2006 6:56 PM
Subject: Re: REFLECTOR: Oil cooler VG photo
> Dave,
>
> Here's another data point for you: I have IO360 Lyc turning a Catto 66 x
> 70" prop on a 173 Elite RG. I have the top NACA scoops, front edge of
> prop
> is 1" from rear of cowl, and I have cylinder wraps that go down below the
> factory air plenum leaving only about an inch to 1.5" gap for the air to
> exit the bottom of the cylinders. I also duct taped the engine crank case
> and laid up 2 bid from the air plenum to the crank case to close up all of
> those gaps Scott talks about.
>
> During our trip to the Symposium, I took a picture of my EIS and other
> panel
> data:
>
> 174 kt IAS
> 2640 RPM
> 22.4 MAP
> 71 deg F OAT
> 320 hottest CHT
> 1362 hottest EGT
> 203 oil temp
> 11.8 GPH
> 29.91 Baro
> 3600 altitude
>
> I also have my oil cooler lines running down separate sides.
>
> The only time my oil temperature will go over 220 degrees is during a take
> off after a quick stop on the ground. Even on 90 degree days. A cruise
> climb 120 kts and reducing power a bit will lower the temperatures below
> 220.
>
> Ronnie Brown
>
>
> ----- Original Message -----
> From: "Scott Derrick" <scott at tnstaafl.net>
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Sent: Sunday, July 16, 2006 4:40 PM
> Subject: Re: REFLECTOR: Oil cooler VG photo
>
>
>> Dave,
>>
>> There has to be things that are different as we are driving the basic
>> same machine.
>>
>> 400 degrees isn't really hot but my CHTs in the summer in cruise were
>> very close to 330-360 range. So I wonder about your overall engine
>> cooling. You say your taking some of your armpit cooling air and using
>> it for induction? I do not. I have a separate ram scoop and use all the
>> arm pit air for cooling.
>>
>> You also didn't mention:
>>
>> Are you running LOP or ROP, makes a big difference in your temperatures?
>>
>> How unobstructed is your oil cooler duct? If you also use that for
>> cabin heat how tightly does the diverter flap come up against the side
>> when cabin heat is turned off? Are their bumps and angles near the
>> outlet that the air has to negotiate or is it a smooth all the way out?
>>
>> Is your baffling really tight, I mean really really tight or do you have
>> big gaping 1/2 inch or inch wide holes where the baffling meets the case?
>>
>> Each of these things won't make a big difference, but added up together
>> they can.
>>
>> Scott
>>
>>
>> Dave Nelson wrote:
>>> Thanks much for the tips, Scott - and for the speedy response. Here's
>>> more
>>> background...
>>>
>>> I have been going after drag reduction to ensure that I remain faster
>>> than
>>> my hangermate (Doug Solinger in his beautiful Cozy Classic). One of the
>>> things I've done is to tighten up air leakage that was occuring between
>>> the
>>> old stock armpit scoops and the lower cowl. I did this by engineering
>>> new
>>> armpit scoops that are a bit smaller. I also created an airbox to use
>>> armpit scoop ram air for induction air (and yes, I did size the scoop
>>> for
>>> this mod). More recently I designed & had built a new exhaust system
>>> that
>>> keeps the entire exhaust internal to the cowl and exits the exhaust
>>> behind
>>> the prop (similar to what you see on alot of long-ezs these days). The
>>> exhaust this new one replaced was purchased from Velocity - the exhaust
>>> gas
>>> exited the lower cowl pointing straight down (and created quite a bit of
>>> drag).
>>>
>>> I've always been focused on ensuring that every molecule of cooling air
>>> I
>>> take in gets used - my plenum is very tight. On a 90 degree day, I
>>> seldom
>>> see any cylinder reach 400 deg. F., which I consider acceptable.
>>>
>>> I am having a BEAR of a time with oil temps, however. I've been working
>>> on
>>> this problem for two years now and I'm about at wits end. I've had
>>> extensive discussions with Lycoming (and others), and I've done all of
>>> the
>>> obvious things (detailed measurements of the vernatherm per Lycoming
>>> specs
>>> to ensure it's working correctly, flushed the entire oil cooling system
>>> to
>>> ensure no "gunk" build up, inverted the oil cooler to put the
>>> connections
>>> at
>>> the top (to eliminate any chance of a bubble), various "scoop"
>>> modifications
>>> to the nose NACA for the oil cooler, MANY test flights (standardized so
>>> I
>>> could gather data)... I even added a bilge fan under the pilot seat to
>>> blow
>>> air into the wiring duct containing the oil lines)... all to no avail.
>>> Where I'm at right now is, a short flight at 25 squared on a 85 degree
>>> day
>>> quickly results in oil temps that have exceeded 225 degrees F.
>>>
>>> I'm at the point of giving in. My current theory is that the oil pump
>>> on
>>> my
>>> engine is no longer as capable of pushing the oil through the approx. 30
>>> feet of tubing as it was when I installed it about 750 hours ago.
>>> Lycoming
>>> tells me that the system is designed for around 4 feet of tubing, and
>>> that
>>> this installation is completely nuts (my words... they are more
>>> diplomatic).
>>>
>>> Sooo... to avoid loosing another summer of flying... I'm now willing to
>>> consider installing a second cooler.
>>>
>>> Any thoughts are welcome - and thanks for the good suggestions!
>>>
>>> Dave
>>> ----- Original Message -----
>>> From: "Scott Derrick" <scott at tnstaafl.net>
>>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>> Sent: Saturday, July 15, 2006 8:57 PM
>>> Subject: Re: REFLECTOR: Oil cooler VG photo
>>>
>>>
>>>
>>>> Dave,
>>>>
>>>> I have Std RG, and had an IO360 200 HP engine in it. Standard oil
>>>> cooler. When I bought the plane I had temp problems. Bad ones.
>>>> Couldn't
>>>> run any where near 75% power without over heating.
>>>>
>>>> I did the following which allowed me to run 75% any time of year and
>>>> normal cruise temps were 190, I even had to cover up some of the oil
>>>> cooler in the winter to get the temps above 180.
>>>>
>>>> 1.) Put turning vanes in the oil cooler duct and smoothed out the
>>>> duct,
>>>> especially the exit. You don't want turbulent air downstream of the
>>>> cooler.
>>>>
>>>> 2.) Got very anal about air leaks in the engine cowl/baffling. Any
>>>> hole larger than 1/4 inch must be plugged. Also be sure the silicone
>>>> baffles are pressed against the engine so that the air pressure will
>>>> tighten them against the heads. Lowering your CHT's will have a
>>>> dramatic effect on your oil temps.
>>>>
>>>> 3.) Run LOP. I installed a Lightspeed Ignition that provided such good
>>>> complete fuel burn I could run 75 degrees LOP which dropped my oil
>>>> temps
>>>> 5-10 degrees from a similar ROP power setting.
>>>>
>>>> Scott
>>>>
>>>>
>>>> Dave Nelson wrote:
>>>>
>>>>> Wow is this both interesting and pertinent to me... I've been battling
>>>>> oil temp issues for the past two summers on my std rg - I'll try the
>>>>> VGs tomorrow.
>>>>>
>>>>> In the meantime, since I'm getting desperate - for those of you that
>>>>> have succumbed and added a second oil cooler - where did you mount
>>>>> it? Where do you get intake air?
>>>>>
>>>>> Thanks.
>>>>>
>>>>> Dave
>>>>>
>>>>> ----- Original Message -----
>>>>> *From:* Laurence Coen <mailto:lwcoen at hotmail.com>
>>>>> *To:* reflector at tvbf.org <mailto:reflector at tvbf.org>
>>>>> *Sent:* Saturday, July 15, 2006 12:46 PM
>>>>> *Subject:* REFLECTOR: Oil cooler VG photo
>>>>>
>>>>>
>>>>> Mike,
>>>>>
>>>>> Here is an attached photo of the VG's. The top VG should produce
>>>>> a clockwise vortex and the bottom one should be counter
>>>>> clockwise. I have no idea as to why you felt a "flutter". The
>>>>> only effect I experienced was cooler oil and nothing else. I felt
>>>>> that my arrangement should stuff air into the oil cooler
>>>>> opening. A 20 degree drop in temperature would logically tend to
>>>>> support the theory.
>>>>>
>>>>> I hope this is of some help.
>>>>>
>>>>> Larry Coen
>>>>> N136LC
>>>>> SE/RG Franklin/IVO
>>>>>
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>>>>
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>>>> Oct. 13, 1785. (*) ME 5:181, Papers 8:632
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