AL,

Thanks for your explanations, there are some intricate details about the Mazda engine that I am either unaware of or don’t fully understand.

I wasn’t aware that the engine out pressure could be 125 psi with the return regulated to 80 psi.  According to the feedback from Fluidyne the coolers are pressure-tested to 300 psi.  My oil cooling capacity has increased tremendously so the flow rate through the coolers must be good; I DID check all lines after a brief engine run, post-install to ensure no leaks and that all lines were hot (that was my low-tech flow test).

One thing I have noticed after installing the second oil cooler, is the oil pressure gauge has some fluctuation or bounce at 5500 rpm that wasn’t there with only one cooler (Mazda or First Fluidyne), so there is a difference, but again I’m not sure why.  It is something that I’ll continue to monitor - we are still flying local.

Jeff

 

 

Al, no I do not measure “before and after”; it’s measured at block output near standard oil filter pedestal and is feed to PSRU input … see attached (this photo  shows the first  cooler input, the pressure sender and the return line from second cooler) … if I understand the oil flow correctly, this is after the coolers.

My max oil pressure was 80 psi when I had one cooler and is still max 80 psi with 2 coolers – typical operating pressure is 75 psi at 5500 rpm.

Jeff

Jeff;

There is a bypass valve in the oil return circuit that regulates the max oil pressure.  That’s probably setup for 80 psi in your engine.  There is also a pressure relief bypass just after the pump exit that is probably for 125 psi (I forget what the stock one is).  So conceivably the drop through the coolers could be 45 psi.

 

Not that it’s a problem as long as there is sufficient flow to maintain the regulated pressure.  But it could be reducing the flow rate, which would reduce cooling capacity, and it could mean there is 125 psi in the lines from the engine; and to the cooler end tank.

 

The geared oil pump is (approximately) a positive displacement pump.  It puts out 13-15 gpm at 5500 -6000 engine RPM.  I just think it’s a good idea to know what sort of pressure drop your dealing with for any oil cooler you put on your engine, other than the Mazda cooler.  I still believe that in the two oil cooler ruptures, and resulting in-flight fires that our friend Chuck Harbert experienced, the pressure drop was a contributing factor.  He had three coolers in series, two up in the nose of a Velocity, along with the concomitant lines and fittings.  The first in the series was the one that ruptured both times.  Undoubtedly running at the pump bypass pressure (whatever that was), coupled with a little fatigue from vibrations in the lines, and pressure ripple from the pump . . . well; just my opinion.

 

Al G