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Ralph,
I think the biggest difference is that when the coolant thermostat blocks flow - the coolant continues to circulate in the block so no part of the block is starved for coolant (although it may be hot coolant {:>)). With the Mazda Oil system IF you block the flow of oil in any way from the oil outlet on the front cover to the oil inlet on the rear iron housing - you have deprived the bearings of pressurized oil. There is no internal feed (like on some engines) in the block from the oil pump to the main bearings, you must have an unobstructed path through the external oil hose for the high pressure pump oil to get to the bearings. If the oil thermostat blocked flow (as does the coolant thermostat) rather than diverting it (around the cooler)- the bearings would be deprived of pressurized oil (not good in the long run {:>).
Ed A
----- Original Message ----- From: "Ralph Reed" <ralph_reed@sil.org>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, August 21, 2005 2:01 AM
Subject: [FlyRotary] Oil Cooler Connections [Thermostat]
I still do not see the difference. The water circulates freely in the block without restriction until the thermostat opens and allows water to run through the radiator. It does open and close a few cycles for a few seconds as it passes through a particular temperature range. Opens, cools off, closes etc. Additionally you have the steam issue so we have to add a pressure release to an overflow that is not an issue with the oil.
The oil is at full pressure running through the appropriate places in the block and when a certain temperature is reached the oil starts making an extra lap around the cooler. Once it starts through the cooler it runs through the cooler until shut down, right?
Okay, everybody outside the box for a second. (That is all it will take an engineer to explain why this would weigh too much!)
The water and the water pump weigh something and the radiator weighs something, all its plumbing weighs something, and the overflow tank and its plumbing weigh something. What if the engine were designed to be cooled by oil alone? I know water transfers faster so how much more oil would you have to have to cool it? There has to be an engineer that knows all about heat transfer rates that could figure this out. How much does this have to do with the specific oil? Light enough to transfer well, thick enough to lubricate.
Blessings, Ralph
----- Original Message ----- From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, August 20, 2005 8:00 PM
Subject: [FlyRotary] Re: Oil Cooler Connections [Thermostat]
You are correct, Bob. You never want your oil flow to be impeded! Which would happen if the oil thermostat worked as the coolant thermostat does. When the oil thermostat is cold, it's by-pass hole is fully open allow most (but not all) of the oil to by pass the cooler. This permits the oil to reach operating temperature quickly as most of it is not being cooled by flowing through the channels of the cooler. Once it reaches its operating temperature the thermostat expands (a plunger extends) plugs the hole and forces all the oil through the oil cooler. As someone mentioned it is very easy to stick the thermostat in backwards. Not realizing how strong the spring was when I unscrewed the one in my cooler the entire assembly blew past the nut (and my hand) and hit the floor disassembled and with me no diagram to show which end was which.
Ed A
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