Bobby,

 

The wastegate control with the used Malibu variable absolute pressure controller seems to work fine.  I didn't use the butterfly type wastegate but made a linkage from the Malibu actuator to the poppet valve type wastegate.  The wastegate is closed until the upper deck pressure reaches the value required by the controller.  Having the wastegate closed even when boost is not required doesn't seem to be a problem since BSFC of close to 0.50 was observed at 23-30" MAP.

 

Oil cooling is another story.  Above 2800 RPM, with a single RX7 cooler, oil is bypassing the cooler either through the relief valve at the oil pump or the relief valve in the oil cooler, depending on the engine series.  If the oil bypass occurs at the oil pump, the temperature of the oil returning from the cooler is often acceptable (210 degrees or less).  If the oil bypass occurs in the oil cooler, the temperature of the oil returning from the cooler is higher due to the mixing of the hot bypassed oil with the oil that has been cooled. 

 

The 13B has a relief valve at the oil pump and one at the flywheel iron.  With a stock relief valve in the flywheel iron, the oil bypass occurs mostly within the oil cooler so keeping the oil returning from it at an acceptable temperature is more of a challenge.  If the flywheel iron relief valve pressure were to be increased, some or all of the bypassed oil would be bypassed at the oil pump (front cover relief valve) instead, making it easier to keep the reduced flow of oil returning from the cooler at an acceptable temperature. 

 

With the 2009 or newer Renesis that is on the engine test stand now,, there is no relief valve in the flywheel iron and the oil pressure downstream of the cooler is normally over 100 psi.  As a result, the oil is bypassed at the oil pump, which makes keeping the oil returning from the RX7 cooler at an acceptable temperature less of a challenge.

 

I haven't worked with the pre-2009 Renesis, but that engine does not have a relief valve at the oil pump and does have one at the flywheel iron.  So at RPM greater than around 2800, oil will be bypassing within the RX7 cooler regardless of the flywheel iron relief valve pressure setting, with the resultant challenge of maintaining acceptable temperatures of the oil returning from the cooler.

 

The behavior of the oil cooling systems described above is just due to the hydraulics of the systems.  Add to this the effects of ducting and airspeed which affect the air pressure differential across the oil cooler core, and things get pretty complicated -- for me, at least.  When measuring the temperature of the oil coming out of the oil pump going to the oil cooler, I didn't like the over 270 degree values I saw.  I also didn't like the oil pressures over 150 psi in the same location.  As a result, I am working on finding an oil cooler solution that does not have the high resistance to oil flow of the RX7 cooler.  The intent is enable all of the oil to pass through the cooler and not require such high oil pressures coming out of the oil pump.  It also requires that more heat be dissipated since now all of the oil is being cooled instead of just some of it.

 

With a single stock RX7 oil cooler, oil would bypass at the oil pump at about 2800 RPM.  Acceptable oil temperatures (210 degrees) returning from the cooler were maintained at 30" Hg MAP on a 55 degree day with 5" H20 air pressure across the core.

 

The next thing I tried was to use an AC evaporator core like the two used as coolant radiators.  On the surface using one of these as an oil cooler might seem to be reasonable since it is usually accepted that one third of the heat rejected by the cooling systems is to be handled by the oil cooler.  With the AC core, the oil flow resistance was such that oil was not bypassing at the oil pump at 5600 RPM, but the oil temperature returning from it was too high.  It appeared that acceptable oil temperatures would be maintained at 30" Hg MAP on a 25 degree day with 5" H20 air pressure across the core.

 

Then two stock RX7 oil coolers were connected in parallel.  They both still had their thermostats installed.  With this configuration, oil would bypass at the oil pump at about 4800 RPM.  It appeared that acceptable oil temperatures would be maintained at 30" Hg MAP on an 85 degree day with 5" H20 air pressure across the cores.

 

The two RX7 oil coolers were then converted to single pass which required removing the thermostats and welding oil line connections to the normally unconnected end tanks.  These coolers were connected in parallel.  Oil would bypass at the oil pump at about 5600 RPM.  It appeared that acceptable oil temperatures would be maintained at 30" Hg MAP on an 85 degree day with 5" H20 air pressure across the cores.

      

After consultation with Fluidyne technical support, a used DB-30517 oil cooler was obtained from an Ebay  source.  When received, the part # stamped on it was DB-30517M and the core dimensions were 9 1/2" X 5 3/4" X 2 1/2" instead of the expected 11 1/2" X 5 3/4" X 2 1/2".  The cooler appeared to be clean inside and undamaged.  With this cooler installed, oil was not bypassing at the oil pump at 5600 RPM (oil psi there was 140).  It appeared that acceptable oil temperatures would be maintained at 30" Hg MAP on a 35 degree day with 5" H20 air pressure across the core.  This performance was considerably less than expected even considering the smaller core volume, both in terms of the oil temperatures achieved and the high oil pressure drop across the cooler.

 

A Fluidyne DB-30617 oil cooler has been obtained and is ready to test.  Core dimensions are 11 1/2" X 9 1/2" X 2 1/2".

 

It looks like the DB-30717 oil cooler that you have is what I might end up with.  I will just have had a lot more "fun" getting to that point.  At least trying things on the test stand is a lot easier than modifying the plane each time.

 

Steve