REFLECTOR: Franklin Oil temp and flow data

[John Tvedte]

Brain,

I am not understanding why you would be concerned about a filter that has a relief valve.  That relief valve works on the pressure difference across the filter media.  Primarily for cold starts, but effective also for the unthinkable clogged filter media.  The oil filter assembly won't block the flow of oil.   An oil filter bypass operates at a reasonably low pressure difference of a few psi - and so it would not 'rob' the circuit pressures of any more than those few psi.

John

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Brian Michalk
Sent: Thursday, November 14, 2013 8:28 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Franklin Oil temp and flow data

On the data I sent out, right after engine start, the engine surged to 1500RPM.  The oil pressure coming out of the engine was 117PSI, the oil pressure returning to the engine was 98PSI.  It wasn't that cold.  70F.

I am measuring the galley pressure where PZL says to measure it, which is off the port on the bypass plate.  I measure the pump pressure right at the oil cooler, which is after about three feet of -10 stainless braided hose.

I am logging 46 unique channels on the airplane.  I am logging more parameters than that, but don't count them, like I count fuel counts and fuel flow as one unique signal.

The more I think about this, the more I am suspecting the oil filter.  I am using the K&N HP-3002, and in looking back at my manual, I had selected the HP-2002.  They are both 550PSI burst pressure, but the 3002 has a PSI relief valve, bypass valve and anti-drain back valve.  The 2002 has none of those.  I probably picked up the 3002 because they didn't have any 2002's on the shelf.

On 11/14/2013 06:54 PM, John Dibble wrote:
On 11/14/2013 1:29 PM, Laurence Coen wrote:
Brian,

There are two valves in the "bypass plate" and they perform independent functions.  The pressure regulator valve sets the oil pump pressure at 80PSI.  That is the maximum pressure that can exists anywhere in the system and is also the maximum pressure that the oil cooler can see.
Well, with the 80 psig spring in the cooler bypass location, at start up on  cold days I would see 99 psig at the cooler outlet (99 is the max reading for my RMI monitor, so it could have been higher).  Seems like the pressure going to the cooler would have been higher yet.

John


  Please note that this has nothing to do with the external loop bypass valve.  Your data would indicate that your statement that no oil flowed for nine minutes is incorrect.  I don't how you are measuring oil flow or where but the fact that there is a differential pressure at the output of the oil cooler and the galley is only possible if there is flow through the cooler.  In a hydrostatic system (no flow) where two points are connected the pressure will be the same.  Your graph shows a differential pressure at opposite ends of a tube connecting the oil cooler and the oil galley.  This indicates oil flow through the cooler from start up to shut down.

Functionally, the Franklin set up works the same as the pressure regulator/"Vernatherm" in a Lycoming.  In a Lycoming, when the oil is cold, The Vernatherm opens a bypass on the oil cooler loop.  When the oil gets hot the Vernatherm closes the bypass forcing the oil to flow through the oil cooler.  On the Franklin the fact that cold oil is thick when cold causes a large drop in pressure through the external loop. This in turn opens the bypass just like the Vernatherm on the Lycoming.  When the oil is hot, the pressure drop in the external loop decreases allowing the bypass to close, just like the Vernatherm did in the Lycoming.  In both cases the pressure regulator simply sets the output pressure of the oil pump.






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