Steve, Dave Cook here, have you tried looking for that same pressure build-up pre Mazda oil cooler with the temp by-pass removed/by-passed, I'm thinking that is the cause of the restriction. David R. Cook RV6A Rotary ,MI
From: "Steven W. Boese" <flyrotary@lancaironline.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, March 23, 2017 12:11:21 AM
Subject: [FlyRotary] Re: fuel system peer review
Andrew,
A Fluidyne DB-30618 is the oil cooler I ended up with in the plane.
When a pressure gauge was installed in the line between the front cover outlet and the RX7 oil cooler inlet, the pressure rose with increasing RPM to 150 psi at 2800 RPM. Increasing RPM above 2800 resulted in a steady pressure at 150 psi. Since the oil pump is a positive displacement pump, additional oil flow above 2800 RPM passes through the relief valve into the sump. At 5600 RPM half of the oil pumped by the oil pump never flows through the oil cooler.
With the Fluidyne oil cooler, the pressure at its inlet never reaches 150 psi so all of the oil passes through it.
An archive search for 25 Feb 2014 should find a description of various oil cooler configurations that I tested.
Steve Boese
From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Andrew Martin <flyrotary@lancaironline.net>
Sent: Wednesday, March 22, 2017 8:40:08 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: fuel system peer review
This thread has perfect timing and great info for me.
I was thinking of ditching my setup and simplifying it, but it looks like every system is a compromise.
I just mounted a belly radiator which entailed moving the pumps & sump tank. As other local pilots had commented on how complex my fuel system was I thought it opportune to address it now. After following this thread though I'm inclined to stick with this setup now as I know it works. and just not let anyone else on the controls.
Only problem I have is I cannot tell the fuel level in the sump tank. Need some sort of warning that I've drained a tank dry or have a vent or feed problem. Am thinking of putting a sight glass in the return line from sump to fuel selectors for a visual clue.
I like this setup as it allows me to feed from any or all tanks. not needed but usually leave 1 transfer pump on. if both transfer pumps happened to fail the fuel return path gives a free flow path from tanks to sump also.
I have managed to empty the sump tank once when flow testing the system but there was no back pressure on the system so regulator was not circulating fuel. I guessed the tank vent lines (1/4") are just to small when fuel flowing at 180l/hr and it vapourized in the sump.
Steve. I'm interested to know the model No. of your fluidyne oil cooler. I started with these mods because I couldn't control my oil temps, so new belly radiator installed to give oil cooler all the cowl air, but I never thought that the mazda cooler may be blocking oil flow. Whats the clue that the front relief valve is opening?
Andrew