Hi George,

The DT is, of course, the amount of temperature rise you get in your cooling air due to heat transfer from you heat exchanger.  Recall  Q = m * DT * Cp - so a 40F DT simply means you must have more m (air mass flow) than if the DT were 100F.  Since air mass flow = Velocity of air * Area (Frontal area of core in this case)  That would generally mean you either need a radiator with a larger frontal  area  and/or your velocity of your cooling air would need to be higher to get the greater air mass flow needed due to a lower DT.  That could add to your cooling drag due to the higher air velocity, but so long as the heat Q being removed is adequate, the engine doesn’t care  what combination of m and DT .

I have seen DT of 100F reported for the radiators by several, but I don’t recall off the top of my head  DT for the oil cooler.  Perhaps somebody who has measured theirs will report it.

Ed

Bill,

Since you didn't direct your question to any specific person, I'll tell you how I set up my engine monitoring system up.  I measure temp and pressure of both the oil and water.  I also measure water level (float switch in the purge tank) as well as the return water temp back into the engine (after the radiator).  So, from this I can tell how well my exchangers are working.  As an example, I normally see a 40* delta-T across the oil cooler.  If this drops, my temps go up and I need to land and find out what's not right.  I also measure coolant pressure.  If pressure is low / high, I need to investigate. 

 

Is this information overload?  Maybe, but I would rather have too much data than not enough.

 

Mark S.

 

 

On Fri, Jan 8, 2010 at 1:08 PM, Bill Bradburry <bbradburry@bellsouth.net> wrote:

Am I correct in my assumption that the engine only has an oil pressure sensor and not an oil temperature sensor?  Is the only engine temperature monitored by the coolant temperature sensor??? 

 

Bill B

 

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From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Jeff Whaley
Sent: Friday, January 08, 2010 1:04 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: water temp probe

Ben, you’re right in that any one probe does not tell the whole story, but specific to the Rotary if only one probe is provided/available then the input oil temperature is most important.  The oil flow diagrams show return oil from cooler is pumped through e-shaft and sprayed inside the rotors for their cooling.  Previous posts and literature state that the rotor oil seals will be damaged by sustained oil temperature >210F.

It is also important to use similar instrumentation to other builders for direct comparison from one installation to the next …

I only measure return oil temperature myself; I’d be interested to know what delta T’s (oil) other builders are seeing.

Jeff

 

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of ben haas
Sent: Friday, January 08, 2010 9:17 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: water temp probe

 

I respectivly disagree on the oil temp sender location. One can have a very efficient oil cooler that removes alot of heat from the oil. Oil  'in' temps are important but,,,, You could possibly have a motor making alot of oil heat and slowing cooking the motor over time and not really know it. Just like with the water temp probe. One needs to know exactly what is happening in the motor in real time...  YMMV.

Ben Haas
www.haaspowerair.com



 

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To: flyrotary@lancaironline.net
Date: Fri, 8 Jan 2010 06:18:39 -0600
From: msteitle@gmail.com
Subject: [FlyRotary] Re: water temp probe

Kevin,

 

I think you want to measure the temp of the coolant as it exits the engine.  That way you know how close you are to your upper operating limit.  If you have a second input, you can measure the temps after the radiator.

 

Oil temps are just the opposite... measure temps after oil has been through the cooler and is entering the engine.

 

Mark S. 

On Fri, Jan 8, 2010 at 12:52 AM, kevin lane <n3773@comcast.net> wrote:

in looking for a place to mount a water temp probe I realized my radiator has a drain plug fitting on the bottom of one of the end tanks that could work.  that portion of the tank has cooled water about to return to the pump.   does it matter if I monitor the before or after radiator temps?  the engine sees both, right?   

same question as to the oil temp probe.  the stock oil cooler has a large fitting [plug?] underneath of one end tank, not sure of its usage.  also have an extra plug in the oil pan [out the side] which might work [?]  told that originally had a oil level sender unit in there.   kevin 

 

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