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  #31  
Old 04-04-2017, 11:21 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by N941WR View Post
Dan Correct me, if I'm mistaken...

By lowering the oil pressure, I believe you give the oil more time in the cooler, to transfer its heat to the moving mass of air.
The oil pump is a positive displacement pump. So the pump output volume is for all practical aspects independent of system pressure (for our closed systems) and constant. I offer that since oil is not a prefect fluid the heat generated by the pumping action might add a marginal amount of heat at a slightly higher pressure - but I'd estimate the additional pumping heat between 65 and 75 psig would be hard to measure.

Oil cooler heat rejection is a function of pounds mass of air and air temp rise across the cooler. Bigger cooler - more heat transfer area and better airflow (pounds mass of air). Better cooler then higher air temp rise across the cooler. Better air pressure drop across the cooler (and everything else constant), more pounds mass of air.

Carl
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  #32  
Old 04-04-2017, 11:38 AM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
The oil pump is a positive displacement pump. So the pump output volume is for all practical aspects independent of system pressure (for our closed systems) and constant. I offer that since oil is not a prefect fluid the heat generated by the pumping action might add a marginal amount of heat at a slightly higher pressure - but I'd estimate the additional pumping heat between 65 and 75 psig would be hard to measure.

Oil cooler heat rejection is a function of pounds mass of air and air temp rise across the cooler. Bigger cooler - more heat transfer area and better airflow (pounds mass of air). Better cooler then higher air temp rise across the cooler. Better air pressure drop across the cooler (and everything else constant), more pounds mass of air.

Carl
Thanks Carl, everything I learned about this stuff in school many years ago, I have forgotten!
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  #33  
Old 04-04-2017, 11:54 AM
BillL BillL is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
The oil pump is a positive displacement pump. So the pump output volume is for all practical aspects independent of system pressure (for our closed systems) and constant. I offer that since oil is not a prefect fluid the heat generated by the pumping action might add a marginal amount of heat at a slightly higher pressure - but I'd estimate the additional pumping heat between 65 and 75 psig would be hard to measure.

Oil cooler heat rejection is a function of pounds mass of air and air temp rise across the cooler. Bigger cooler - more heat transfer area and better airflow (pounds mass of air). Better cooler then higher air temp rise across the cooler. Better air pressure drop across the cooler (and everything else constant), more pounds mass of air.

Carl
The oil does collect air to about 5-8%. Right on the pressure, with that increase the pumping loss would be higher but with 95% efficiency already, marginal, and the total flow would also incrementally be lowered, although the various paths to the sump will change. Nothing jumps out as to why it would have such a pronounced effect on the oil temps. Unless a baffle seal was pushed back into place in the process.
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  #34  
Old 04-04-2017, 07:13 PM
Timberwolf Timberwolf is offline
 
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probes tested and all are fine. I got a chance to get it up and cruise around a bit today and the CHT's really came down. Still something going on but oil temps are steady around 195-200. It'll get me to SNF and back until I have more time to mess with the 4" scat tube to the cooler. Thanks to everyone for the help. Will post up more after I get a chance to mess with it some.
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  #35  
Old 04-04-2017, 07:58 PM
Robb Robb is offline
 
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It looks like the cooler is discharging towards the firewall? If so it needs turned down towards the bottom it will never work as well like it is
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  #36  
Old 04-05-2017, 05:26 AM
trifield trifield is offline
 
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Default Oil temps

Just for the record , I have an enclosed plenum, 4inch scat to 13 row cooler, 25' timing . As said previously nothing has changed the temps as dramatically as winding down the oil pressure. I would not have posted my results if it was possibly something else .
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  #37  
Old 04-05-2017, 06:03 AM
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Quote:
Originally Posted by trifield View Post
Just for the record , I have an enclosed plenum, 4inch scat to 13 row cooler, 25' timing . As said previously nothing has changed the temps as dramatically as winding down the oil pressure. I would not have posted my results if it was possibly something else .
I have a theory, something I've been kicking around a while. At s&f on a cell phone, more later
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  #38  
Old 04-05-2017, 06:24 AM
salto salto is offline
 
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You could try running your oil quantity a bit closer to minimums.
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  #39  
Old 04-05-2017, 09:54 AM
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MarkW MarkW is offline
 
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Quote:
Originally Posted by DanH View Post
I have a theory, something I've been kicking around a while. At s&f on a cell phone, more later
I got to hear this. See ya tomorrow.
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  #40  
Old 04-05-2017, 10:01 AM
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bret bret is offline
 
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Could the higher oil pressure been fighting the spring on the vernathurm and therefor holding it off the seat allowing some oil bypass and not full direction to the cooler?
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