Differences

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--- techtalk:ih:oil03 [2019/12/21 01:52]
hippysmack [Priming the Oil Pump]
+++ techtalk:ih:oil03 [2020/11/07 04:29]
hippysmack [Oil Pump Pressure (57-85)]
@@ Line 16: / Line 16: @@
     * [[techtalk:ref:oil06|Comparing the 77 Style Oil Pump to Newer Pumps]]
+====== Oil Pump Function ======
-===== Production Oil Pumps =====
+The oil pump is a positive displacement unit. \\
+If you block the discharge flow path, discharge pressure will rise and literally approaches infinity until something fails. ((BuckIRyder of the XLFORUM http://xlforum.net/forums/showthread.php?t=730325&page=2)) \\
+It's non-regulated and delivers its entire volume of oil under pressure to the oil filter mount. \\
+However, don't take the term "positive displacement pump" literally. ((Dr Dick of the XLFORUM http://xlforum.net/forums/showthread.php?t=1429178&page=2)) \\
+Compared to a centrifigal pump, gear / gerotor type pumps use displacement to function. \\
+How positive it is depends on what it's pumping. \\
+The most 'positive' pump on our bikes may be the master cyl for the disc brakes. \\
+You pull the lever and it pumps real good, positive, unless there is air in the system. \\
+Then you still get the displacement but not the pressure because liquid is not compressable but air is. \\
+Gear / gerotor type pumps work by filling the spaces between the teeth with whatever it is that is being pumped (oil in our case). \\
+The oil in the tooth spaces gets squezed out of the spaces when the gear teeth mesh together (because a tooth is now in that space. \\
+But there is still a little space left at full mesh. \\
+Gearotor pumps have a smaller space at full mesh than gear pumps. \\
+Now when the mesh breaks, a void is created. Oil gets sucked into that void. \\
+Now what if air is in the spaces instead of oil? \\
+It gets sqeezed out also unless there is pressure (restriction) in the curcuit its trying to flow into. \\
+In that case, some air stays in the spaces and gets compressed in the small space remaining as the teeth mesh. \\
+When the teeth unmesh, air expands (refilling void that should be getting oil sucked into it. \\
+The pump can't make enough pressure to overcome the exit restriction. \\
+Then there is no flow and no ability to reprime itself since. \\
+(it's not making enough suction due to the expansion of the compressed air refilling the void that the oil should be filling) \\
+Eventually the pressure in the return line gets released. \\
+While this is happening oil is building up in the pickup sump and waiting for the return side to come back online. \\
+The supply pump is still pumping while the return is toggling from air locked to primed and pumping. \\
+Think about what state the return oil is in as it collects in the return pickup cavity. It's just been thru a 60 cycle blender. \\
+Our bikes live with that every mile they travel with lots of air whipped into every drop of return oil. \\
+Restrictions in the return side of the pump will lead to a more sustained oil level in the crankcase sump. \\
+(large enough to reduce outflow from the engine to a volume less than the supply pump is feeding the engine) \\
+This is a condition known as wetsumping. \\
+Read more about [[techtalk:ref:oil10|wetsumping]] in the REF section of the Sportsterpedia. \\
+===== 57-76 Oil Pumps =====
   * There are 3 basic pumps & 2 basic plumbing styles ((Dr Dick of the XLFORUM http://xlforum.net/forums/showpost.php?p=3272806&postcount=204))
@@ Line 111: / Line 149: @@
       * The oil pump speeds were doubled to 1/2 of engine speed for the feed pump and a 4:1 ratio on the return side.
       * The oil pump drive gear was re-activated as a breather only. ((1972-2003 HD XR-750 Service Manual pg 27))
-====== Oil Pump Pressure (57-85) ======
-Engine oil pressure was measured (by the MoCo) with a pressure gauge at the oil pump. \\
-Expected oil pump pressure per FSM's: \\
-**Gauge mounted at oil pump**: \\
-As checked with hot oil and a gauge at the oil pressure switch location at the oil pump. \\
-The oil pressure switch has to be removed for the gauge to be installed. \\
-**1957-1969**: ((1959-1969 HD FSM pgs 3A-11, 3A-15)) \\
-Minimum: 3-7 psi (idle, with spark retarded) \\
-Normal riding conditions: 10-14 psi (6 psi at 20 mph) \\
-**1970-1978**: ((HD 70-78 FSM pgs 3-1, 3-5)) \\
-Minimum: 3-7 psi (idle) \\
-Maximum: 15 psi (60 mph in high gear) \\
-Normal riding conditions: 4-15 psi
-**1979-1985**: ((1979-1985 HD FSM pgs 3-1, 3-10)) \\
-Minimum: 4-7 psi (idle) \\
-Maximum: 10-20 psi (3500 rpm) \\
-Normal riding conditions: 4-15 psi \\
-**Note**: On a cold startup, expect pressure to reach ~60 psi ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=1456449)) \\
-{{:techtalk:ih:oil:oil_pressure_gauge_1_by_dieselox4.jpg?direct&300|}} ((photo by Dieselox4 of the XLFORUM http://xlforum.net/forums/showthread.php?t=1456449)) {{:techtalk:ih:oil:oil_pressure_gauge_2_by_dieselox4.jpg?direct&300|}} ((photo by Dieselox4 of the XLFORUM http://xlforum.net/forums/showthread.php?t=1456449))
@@ Line 172: / Line 182: @@
 {{:techtalk:ih:oil:77-_85_oil_pump_drawing_by_hippysmack.jpg?direct&400|}} ((drawing by Hippysmack)) {{:techtalk:ih:oil:77-85_oil_pump_feed_transfer_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack))
   * This pump has two hose fittings; ((ironheadjunkie of the XLFORUM http://xlforum.net/forums/showthread.php?t=1400314&page=2))
@@ Line 181: / Line 190: @@
     * Then, the oil will return from the front fitting of the oil pump to the oil tank.
+{{:techtalk:evo:oil:oil_pressure_switch_threads_by_hippysmack.png?direct&300|}} ((drawing by Hippysmack)) \\
 ===== Production Oil Pumps =====

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