REFLECTOR: Oil cooler VG photo

Scott Derrick scott at tnstaafl.net
Sun Jul 16 15:40:10 CDT 2006


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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>>
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