REFLECTOR: Oil cooler VG photo
Scott Derrick
scott at tnstaafl.net
Mon Jul 17 14:00:05 CDT 2006
Chuck,
I guess we will have to agree to disagree. I base my conviction about
the "direct" correlation on experience, not what somebody has told me.
When I bought my V, I had high CHT's and oil temps. I could not run at
75% power except in the coldest of winter.
I had a standard nose mounted oil cooler, both lines in the same duct.
The first thing I did to cure the problem was fix the oil cooler duct;
put turning vanes in it, modify the cabin heater diverter flap so it
laid all the way flat in the duct when cabin heat was off and make the
duct smooth with as few bumps or constrictions that would impede the
air flow after the cooler. This helped, I got about a 10 degree lowering
of the oil temps.
The second thing I did was get very anal about closing all the holes in
the engine baffles and cowling. I had teh standard updraft cooling.
There were huge leaks around the exhaust pipes and baffling. Once I did
this my CHT's dropped from an average 400 to an average 330, my oil
temps dropped from 225-235 to 210-220.
This reduction in oil temps that came about by improving the cooling of
the cylinder heads and thus reducing the CHT's has convinced me that
there is a direct correlation between high CHT's and high oil temps.
Running LOP also will reduce your oil temps 5 to 10 degrees.
Scott
Chuck Jensen wrote:
> Scott,
>
> Far be it from me to defend Lycoming (after all they've pretty well
> given everyone the 'shaft', and made them pay for it), but there is, at
> best, a loose correlation between CHT and oil temps. The CHTs would
> have to go massively high before they transferred enough heat to the oil
> to affect it appreciable and vice versa. They are both on the same
> engine and two separate and semi-isolated systems. Ultimately, if one
> or the other gets too extreme, the engine will go quiet and the
> relationship between the two will not be uppermost on our minds.
>
> What is common to both the CHTs and oil temps is good cooling air flow.
>
> Chuck
>
>
>
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
>>
> On
>
>> Behalf Of Scott Derrick
>> Sent: Sunday, July 16, 2006 10:38 PM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: Oil cooler VG photo
>>
>> 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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>>>>>>>
>>>>>> --
>>>>>>
>>>>>> -
>>>>>> The most effectual engines for [pacifying a nation] are the
>>>>>>
> public
>
>>>>>> papers... [A despotic] government always [keeps] a kind of
>>>>>>
> standing
>
>> army
>>
>>>>>> of newswriters who, without any regard to truth or to what should
>>>>>>
> be
>
>>>>>> like
>>>>>> truth, [invent] and put into the papers whatever might serve the
>>>>>> ministers.
>>>>>>
>>>>>> Thomas Jefferson to G. K. van Hogendorp
>>>>>> Oct. 13, 1785. (*) ME 5:181, Papers 8:632
>>>>>>
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>>>>>>
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>>>>>
>>>>>
>>>>>
>>>> --
>>>>
>>>> -
>>>> The only security of all is in a free press. The force of public
>>>> opinion cannot be resisted when permitted freely to be expressed.
>>>>
> The
>
>>>> agitation it produces must be submitted to. It is necessary, to
>>>>
> keep
>
>> the
>>
>>>> waters pure.
>>>>
>>>> Thomas Jefferson to Lafayette, 1823. ME 15:491
>>>>
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>> --
>>
>> -
>> Liberty means responsibility. That is why most men dread it.
>>
>> George Bernard Shaw, Liberty
>>
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