REFLECTOR: Oil cooler VG photo
Scott Derrick
scott at tnstaafl.net
Sun Jul 16 21:37:34 CDT 2006
Ron,
Your Cylinder head temps are much more in line to what I have. When I
had CHT's up in the high 300's I also had high oil temps. It makes
sense, our engines are not just air cooled, they are oil cooled also. I
can't believe Lycoming would suggest there is no correlation between
CHT's and oil temps.. But then they also say that LOP is bad, heads
firmly inserted mode.
I think if Dave got his CHT's under control its a high probability his
oil temps come down to a normal range...
Scott
Ron Brown wrote:
> 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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