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Hi Joe,
Sorry to hear about your oil cooling problem, but if its any consolation your problem is not a new one {:>).
If you oil cooler is cool on the end furthest from the oil inlet/outlet thermostat then it clearly is not getting hot oil. As several have already suggested your oil thermostat must indeed be open and diverting the oil from the core where it would be cooled. I have not tried plugging the thermostat hole, so can offer no suggestions - besides, I would hesitate to remove the thermostat. One of its functions is to have oil bypass the core when the oil is cold so that it can warm up quicker, but perhaps more important it can also provide a pressure relief function when the ambient air is very cold and preventing the excessive pressure of cold "thick" oil from building up in the oil cooler core.
Regarding your other approaches to solving your cooling.
One of the most important things I have learned about cooling is that it is very, very important that you do not have turbulent eddies near the entrance of your cooling duct. Such eddies in effect cast an ever expanding "shadow" down stream over the cooling core reducing the effectiveness of the section of core "covered" by the shadow of turbulent air. These eddies are primarily a result of a detached boundary layer of air next to the walls of the duct. So expanding your inlet will not necessarily result in more effective cooling if your inlet has eddies forming near the entrance - in effect you simply have more of your core frontal surface under the eddies shadow.
From my reading, it appears that the most effective duct (that I am aware of) is the streamline duct. Basically there is little expansion (enlargement) of the duct cross section until just before the core. The streamline duct profile looks like a trumpet with the bell end against the core. This approach keeps the air velocity high in the duct (reducing boundary layer separation) until the last moment where the duct is rapidly expanded into the trumpet bell just before the core. While separation will occur there, any eddy formed along the wall is so close to the core that its "shadow" is smallest and therefore more of the core is exposed to effective cooling air flow.
Second, its important to have your core exit area at least 10-12" from any flow obstacle. Obviously, these are idea conditions and can rarely be met within the constrains of our aircraft space. But, the idea is to adhere as closely as you can to them.
It took me five modifications before I finally found success in reducing my oil cooler temperature. But, once the oil temp problem was solved then the coolant temps fell into place
Good luck and keep at it
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message ----- From: "Joe Hull" <joeh@pilgrimtech.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, June 15, 2006 6:06 PM
Subject: [FlyRotary] Re: Oil Cooling Issues
I used Pacific Oil Cooler Service to overhaul/clean/inspect my Mazda oil
cooler and they did a great job. If you tell them it is an automobile
oil cooler and not an aircraft oil cooler, they will charge a lot less.
I paid $112 in 2001.
Here is a link to their website.
http://www.oilcoolers.com/overhaul_service.htm
That link is a keeper! THANX!
Joe Hull
Cozy Mk-IV #991 (In Phase1 Flight Test - 29.1 hrs flown)
Redmond (Seattle), Washington
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