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--- techtalk:ref:oil21 [2022/09/05 03:57]
hippysmack [Oil to / from the pressure chamber]
+++ techtalk:ref:oil21 [2024/04/04 01:27] (current)
hippysmack [Flow Rate Chart for Water]
@@ Line 35: / Line 35: @@
 In that case, the static pressure would go down to around .225 PSI at operating temp. \\
-Lowering the oil level to the low mark on the dipstick will lower the pressure at the oil pump. \\
+Lowering the oil level to the low mark on the dipstick will lower the pressure at the oil pump slightly. \\
+But it is not gravity that actually pulls oil into the pump. It's vacuum created by the gears / gerotors that does most of the oil gathering. \\
+A change in location elevation from sea level can also change the pressure at the oil pump. \\
 The mark is there as a minimum oil level to attain enough pressure at the pump to keep down cavitation in the oil pump. \\
-A change in location elevation from sea level will change the pressure at the oil pump. \\
-The roughness of the feed hose ID will lower pressure at the pump due to the affects of friction. \\
+Below are some examples of things that could lead to pump cavitation; \\
-Kinks in the feed hose or internal shrinkage of the inside walls of the feed hose will lower pressure at the oil pump. \\
+  * The roughness of the feed hose ID can lower pressure at the pump due to the affects of friction.
-Changing the inlet fitting to a smaller ID will lower pressure on the hose side of the fitting. \\
+  * Kinks in the feed hose or internal shrinkage of the inside walls of the feed hose can lower pressure at the oil pump.
-The static pressure at the inlet is changed further upon vacuum from the oil pump inlet. \\
+  * Changing the inlet fitting to a smaller ID can lower pressure on the hose side of the fitting. \\ The static pressure at the inlet is changed further upon vacuum from the oil pump inlet. \\ The hose fitting is a restriction where flow (from vacuum)of pump gear action lowers static on the hose pressure. \\
-The hose fitting is a restriction where flow (from vacuum)of pump gear action lowers static on the hose pressure. \\
 {{:techtalk:ref:oil:sportster_oil_pressure_-_oil_tank_head_pressure_by_hippysmack.png?direct&400|}} ((drawing by Hippysmack)) \\
@@ Line 134: / Line 135: @@
 |  1977-E1983 Sportster Oil Pump Feed \\ Gerotor Positions - Supply Side ((photo by Hippysmack))  |  1977-E1983 Sportster Oil Pump Feed \\ Gerotor Positions - Feed Side ((photo by Hippysmack))  |
 |{{:techtalk:ref:oil:sportster_oil_pressure_-_oil_pump_supply_side_by_hippysmack.jpg?direct&400|}}|{{:techtalk:ref:oil:sportster_oil_pressure_-_oil_pump_feed_side_by_hippysmack.jpg?direct&400|}}|
 ====== Oil Pump Suction ======
@@ Line 199: / Line 199: @@
 |  Video of no vacuum pressure w/ no oil in hose ((video by Hippysmack))  |
-|{{:video:oil_pump_flow_testing_video-_vacuum_on_pump_return_port_by_hippysmack.mp4|}}|
+|{{video:100-oil_pump_flow_testing_-_vacuum_on_pump_return_port_by_hippysmack.mp4|}}|
 ====== Oil Pump Internal Oil Leakage ======
@@ Line 232: / Line 232: @@
 However, the efficiency of positive displacement pumps increases as the pressure increases. \\
 At low RPM, the percentage of slip in relation to volumetric displacement is higher than at high speed. ((https://www.pumpindustry.com.au/pump-school-when-to-use-a-positive-displacement-pump/)) \\
 ==== Affects of Viscosity ====
 As mentioned above, there is always a certain amount of internal leakage in a pump that is within clearance range. \\
@@ Line 308: / Line 309: @@
   * **Scratches on gerotor riding surfaces**: \\ The surface in the housing or cover where the gerotors ride can get scratched from grit or debris traveling with the oil. \\ Debris caught between the teeth rotate across the dividers between the inlet and outlet cavities gouging the divider(s). \\ This has been noticed more on the larger divider pad although scratches do appear on both dividers (especially 1977-1990 oil pumps). \\ This has also been noted more on the return gerotors than the feed side. \\ Broken motor internals go thru the return side first, then the oil tank. \\ Heavier pieces fall below the feed outlet in the oil tank. \\ So for bits of motor internals to get to the feed side to score it up, they first had to travel to the retrun side, possibly scoring that up initially. \\ The feed gerotors are open across the large pad and it's easier to trap debris between the inner and outer teeth while dragging it across the pad. \\ Minor scratches can be from grit in the oil being dragged across the pads when gotten under the gerotors. \\ So there could be multiple scratches with multiple causes over time on the divider pads in the oil pump. \\ The gerotors are designed to ride against flat surfaces. Scratches in the riding surfaces can allow oil to recirculate (outlet to inlet). \\ This will lower the amount of flow that goes to the engine by however much oil can make it through the scratches. \\ This can also lower static pressure on the feed side especially on sustained idle or lower RPM if the scratches are deep enough. \\ \\ 1977-1990 Sportster oil pumps will have more of a tendency for deeper scratches in the cover than later oil pumps. \\ This is due to the two divider spacers (1 each on feed and return gerotor facing each other) with a spring washer between them. \\ The spring washer will allow the gerotors to jerk down or up on impact. \\ There is a space between the plates that separates feed and return gerotors held away from each other with the spring washer. \\ Debris caught between gerotor teeth can cause the gerotors to jump up/down allowing debris to get under them. \\ This allows larger debris to be dragged through both the large and small cavity divider plates leaving deeper scratches on pump cover. \\ \\ How much pressure loss would depend on the width, depth, length of the scratches, oil viscosity at the time and engine RPM. \\ Idle / Low RPM will allow the most leakage (recirculation). \\ Higher RPM brings higher pressure to the outlet side and more pressure drop toward the inlet side = less internal oil leakage. \\ Hot oil flows faster than cooler oil. Higher heat lowers viscosity even more. \\ As viscosity lowers, oil flows faster, especially at idle. \\ Deep scratches will recirculate more oil than shallow ones. \\ Deep scratches recirculate more oil on high RPM than shallow ones.
-|Metal chunk lodged in return inlet. \\ The one medium scratch on big pad is some concern. \\ Small amount of recirculation oil internally. \\ Metal debris lessens amount of pickup oil at once.  \\ May be reusable with further observation ((photo by sc72 of the XLFORUM http://xlforum.net/forums/showthread.php?t=1717592&page=15))|Deep and wide channel ripped into big pad. \\ Light scratches across small pad. \\ High possibility of recirculating oil internally, \\ (feed outlet to feed inlet thru big pad scratch) \\ Owner said oil was not returning. \\ Should be replaced. ((photo by Rolli of the XLFORUM http://xlforum.net/forums/showthread.php?p=5877838&highlight=oil+pump#post5877838))|A gearshaft pin sheared and got into the return cavity. \\ It broke out a corner of the big pad. \\ The remaining flat surface of pad is undamaged. \\ Should be reusable with further observation. ((photo by DirtyCory of the XLFORUM http://xlforum.net/forums/showthread.php?t=1297584&page=2))|
+|Metal chunk lodged in return inlet. \\ The one medium scratch on big pad is some concern. \\ Small amount of recirculation oil internally. \\ Metal debris lessens amount of pickup oil at once.  \\ May be reusable with further observation ((photo by sc72 of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/160106-where-to-go-from-here/page15?t=1717592&page=15))|Deep and wide channel ripped into big pad. \\ Light scratches across small pad. \\ High possibility of recirculating oil internally, \\ (feed outlet to feed inlet thru big pad scratch) \\ Owner said oil was not returning. \\ Should be replaced. ((photo by Rolli of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/201663-1983-ironhead-oil-not-returning?highlight=oil+pump#post4475667))|A gearshaft pin sheared and got into the return cavity. \\ It broke out a corner of the big pad. \\ The remaining flat surface of pad is undamaged. \\ Should be reusable with further observation. ((photo by DirtyCory of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/127032-getting-this-78-back-to-the-way-it-should-be/page2?t=1297584&page=2))|
 |{{:techtalk:ih:oil:1983_sportster_oil_pump_body_by_sc72.jpg?direct&300|}}|{{:techtalk:ih:oil:1977-e1983_oil_pump_scratches_by_rolli.jpg?direct&300|}}|{{:techtalk:ih:oil:1978_oil_pump_body_by_dirtycory.jpg?direct&300|}}|
@@ Line 396: / Line 397: @@
 Friction in the feed passages creates higher static (gauge) pressure. The higher the flow rate, the higher the affects from friction. \\
 See below. \\
 ====== Friction Loss ======
 Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. ((https://byjus.com/physics/fluid-friction/)) \\
@@ Line 769: / Line 771: @@
 Meanwhile, the inside of the motor is creating higher temps. \\
 The oil reacts to the temp of it's surroundings (metal around it heats up, oil heats up because of it). \\
-So if the heat coming off the motor is blown away from it, that keeps the that heat from staying close to the motor and reaching even higher temps. \\
+So if the heat coming off the motor is blown away from it, that keeps the heat from staying close to the motor and reaching even higher temps. \\
 It also keeps the oil inside from reaching higher temps but air while riding down the road doesn't actually cool the oil. \\
 The oil inside the motor doesn't directly receive the benefit of outside air flow. \\
@@ Line 912: / Line 914: @@
 |  Pic of recirculation zone ((photo by Hippysmack))  |  Video showing recirculation zone ((video by Hippysmack))  |
-|{{:techtalk:ref:oil:sportster_oil_pressure_-_orifice_3_vena_contracta_by_hippysmack.jpg?direct&400|}} ((photo by Hippysmack))|{{:video:oil_pump_flow_testing_video-_recirculation_past_an_orifice_by_hippysmack.mp4|}} ((video by Hippysmack))|
+|{{:techtalk:ref:oil:sportster_oil_pressure_-_orifice_3_vena_contracta_by_hippysmack.jpg?direct&400|}} ((photo by Hippysmack))|{{video:100-oil_pump_flow_testing_-_recirculation_past_an_orifice_by_hippysmack.mp4|}} ((video by Hippysmack))|
 ====== Flow Rates ======
 Velocity through a line can be calculated with the formula: Velocity (FPS) = (GPM x 0.3208) ÷ Area
@@ Line 926: / Line 928: @@
 ===== Flow Rate Chart for Water =====
 These figures are for water through orifices and do not represent oil flow through orifices. \\
-Oil flow at operating temp will be differnet due to oil having a higher viscosity. \\
+Oil flow at operating temp will be different due to oil having a higher viscosity. \\
 Water is basically regarded as having no viscosity. \\
 The chart below is a reprint from Senninger.com. ((https://www.senninger.com/sites/senninger.hunterindustries.com/files/nozzle-flow-sheet.pdf)) \\
@@ Line 1129: / Line 1131: @@
 The pic below is from a 1998 XL1200S, same flywheel assembly used on all 1995-1999 Sportsters. \\
 {{:techtalk:ref:oil:sportster_oil_pressure_-_1998_flywheel_oiling_hole_dims_by_hippysmack.jpg?direct&400|}} ((photo by Hippysmack)) \\
-====== Hydraulic Lifters (tappets) ======
-System oil pressure goes all the way thru the lifters to the rocker boxes. \\
-However, system pressure at the lifter bore is restricted several times before it gets delivered into the pushrod tubes to the rocker arms. \\
-Pressure and flow is lowered entering the path to the plunger, further lowered to the reservoir, further lowered entering the pushrod. \\
-System pressure also builds (from a lowered state) during the process by wide oil bands, the plunger reservoir and of course engine valve pressure. \\
-Examining internal lifter oil paths from the lifter bore to the rocker arms will show some of these dynamics. \\
-{{:techtalk:ref:oil:1991-1999_sportster_lifter_body_internals_by_hippysmack.jpg?direct&400|}} ((photo by Hippysmack)) {{:techtalk:ref:oil:1991-1999_sportster_lifter_cutaway_by_hippysmack.jpg?direct&400|}} ((photo by Hippysmack)) \\
-==== Oil to the lifter body ====
-System oil pressure is fed through the lifter bores into the outer oil band that circles the lifter body. \\
-Oil circles around the lifter body's outer oil band and finds it's way into the oil inlet hole above the oil band. \\
-There is a machined taper above the outer oil band up to the inlet hole that allows oil to rise to the inlet. \\
-The hole is angle drilled in the lifter body so that it opens into the oil band of the plunger body. \\
-The inlet hole is much smaller than the feed path. So system pressure is reduced past the hole. \\
-A smaller amount of flow runs (faster) through that drilled passage through the lifter body wall. \\
-In the drawing below, dims were taken from a 1998 1200S lifter and bore showing that oil feed is never blocked to the lifter. \\
-The cams are Andrews N-4s so actual lift may vary. However, the feed hole in the bore should be the same for at least 1991-1999 Sportsters. \\
-{{:techtalk:ref:oil:1998_sportster_lifter_to_bore_feed_hole_relationship_by_hippysmack.png?direct&500|}} ((drawing by Hippysmack)) \\
-==== Oil to the plunger reservoir ====
-Oil from the lifter body inlet enters a small area between the inner body and outer plunger body. \\
-The clearance between body and plunger is tiny. \\
-This tight clearance allows the plunger to move up and down without metal to metal contact to the lifter body. \\
-The clearance creates a sliding oil seal between them in operation, allowing back pressure to build. \\
-Increased wear, opening up this clearance between these walls, can reduce pressure to the rocker arms. \\
-Side note: The restricted orifice in the pinion shaft allows pressure to build at the lifter bores as well. \\
-Without the pinion shaft restriction, there wouldn't be as much pressure to push oil through the restricted lifter holes. \\
-The internal clearance between body and plunger is also where the lifter bleeds off (very slowly) when the cam is off the base circle (as the lobe rises and falls). \\
-Due to the tight oil seal between the lifter body and plunger, oil pressure can be transferred through the path to the rocker arm. \\
-There is an inner oil band in the body that mates around an outer oil band of the plunger between the clearance zones between them. \\
-The oil here is subject to variable pressure changes as the plunger rises and falls due to oil band construction and position. \\
-The oil bands pocket depths are different and the combined dimension when they meet up changes depending on plunger positioning. \\
-Oil is transferred to the plunger inlet by way of these two oil bands meeting together forming a single (circular) path. \\
-With the cam on it's base circle, the combined dim is the widest and most the highest amount of oil flow gets to the plunger reservoir, thus rocker arms. \\
-As the cam lobe rises, the combined dim decreases and the least amount of oil is sent to the reservoir. \\
-This lowers oil flow to the reservoir and rocker arms until the cam returns to it's base circle once again. \\
-The plunger has an oil inlet in the middle of the surrounding oil band that allows oil to enter the reservoir inside. \\
-The oil bands insure oil transfers to the plunger reservoir inlet hole  (no matter of it's positioning). \\
-The plunger is free to rotate invariably both during assembly and when not under load. \\
-{{:techtalk:evo:oil:1991-up_sportster_lifter_anatomy_by_hippysmack.png?direct&400|}} ((drawing by Hippysmack)) \\
-==== Roll of the check disc ====
-Sitting under the plunger is a thin metal disc with no holes in it that blocks oil from entering / leaving the pressure chamber below. \\
-The disc has a spring below it and the spring tension comes from a metal cage that presses the assembly together. \\
-The metal cage presses onto a boss under the plunger. \\
-The check disc allows oil to leave the pressure chamber when the cam lobe ramp initially rises off the base circle. \\
-This pushes the lifter body up creating a fast heavy vacuum in the pressure chamber that opens the check disc. \\
-Oil from the plunger reservoir is sucked into the pressure chamber by vacuum. \\
-Immediately afterwards, pressure begins building in the chamber due to the pushrod now rising toward engine valve spring pressure. \\
-Rising pressure in the chamber pushes the check disc closed against the bottom of the plunger. \\
-With the check disc closed and oil being non compressible, the lifter now acts as a solid lifter all through cam lobe lift duration. \\
-Downward pressure isn't relieved until the cam rolls back around to it's base circle. \\
-(remember, you should be able to turn the pushrod by hand when the cam is on the base circle) \\
-Downward pressure subsides in the lifter's pressure chamber but the previous cycle squirted some of that oil into the reservoir. \\
-The pressure chamber is now low of oil and there would be a gap (lash) between the pushrod and rocker arm. \\
-But when the pressure is relieved off the pushrod / pressure chamber, the plunger return spring returns to it's normal height. \\
-The plunger rises and a mild vacuum pulls the check disc off it's seat. \\
-Positive static pressure in the reservoir assists timely chamber filling as the spring closes very fast when the plunger rises. \\
-==== Oil to / from the pressure chamber ====
-**Oil is forced out of the pressure chamber into the reservoir when the cam lobe initially rises**. \\
-As the camshaft rotates and opens the engine valve, the pushrod (thus the lifter's plunger) is forced down toward the bottom chamber. ((https://mooregoodink.com/all-pumped-up-understanding-hydraulic-valve-lifters/)) \\
-The downward force of oil in the plunger reservoir opens the check disc toward the lower chamber. \\
-The (now open bottom) plunger is moving down into the lower chamber filled with oil. \\
-Some of the oil in the lower chamber is squeezed up past the open check disc into the plunger reservoir. \
-With the check disc open, the lower chamber volume decreases as the plunger is continuously forced toward it by increasing engine valve spring pressure. \\
-This increases oil pressure in the lower chamber forcing the check disc to close toward the plunger. \\
-As oil is considered incompressible, the plunger can no longer move since oil is trapped under it in the lower chamber (except thru the very tight clearance). \\
-The lifter now operates as a solid lifter and transfers the motion from the camshaft lobe to the pushrod / rocker arm. \\
-**Oil is allowed into the pressure chamber from the reservoir when the cam is on it's base circle**. \\
-During the lift of the camshaft and due to valve spring pressure, some of the oil in the pressure chamber is forced from the lifter cavity by the time of max lift. \\
-Once the cam rotates back to it's base circle, the pressure from the pushrod is decreased on the plunger and it enters its at-rest position. ((https://mooregoodink.com/all-pumped-up-understanding-hydraulic-valve-lifters/)) \\
-Then the big spring under the plunger pushes the plunger up creating a negative pressure in the chamber thus opening the check once again. \\
-Plunger reservoir oil pressure quickly slips thru the check disc opening into the pressure chamber and the check closes under it's own spring pressure. \\
-The pressure chamber is now replenished with oil and ready for the next cycle.
-This also re-sets the plunger height taking up the clearance between the pushrod and rocker arm creating zero lash. \\
-==== Oil to the rocker arms ====
-Oil is not allowed to simply flow straight through from the plunger reservoir up into the pushrod. \\
-Sitting atop the plunger reservoir is a thin metal disc with 4 small holes (metering disc) drilled through it. \\
-Oil has to run through these holes to further the path up top. \\
-The holes are in the neighborhood of .090" each. This might not sound like a lot metering. \\
-But oil through these holes gets restricted once again by the pushrod cup directly on top of the metering disc. \\
-The pushrod cup mates to the metering disc by way of pressure just like the pushrod seals to the cup by way of pressure. \\
-However, there is a machined inner cavity on the bottom of the cup where oil through the metering disc lands. \\
-Oil circulates around the bottom of the cup until it reaches the center where there is another restriction in the path. \\
-The cup machining basically creates a dish on the inside bottom where the sides and the center mate to the metering disc. \\
-The center has a small slot milled out for oil to enter it, turning North up through the center into the pushrod. \\
-The dish on the bottom is app 0.015" deep, the center slot is app .008" deep and app 0.77" wide. \\
-So there is a lot more oil that can pass through the metering disc than what can get through the cup's center all at once. \\
-The restrictions in the pushrod cup also ensure that there will be back pressure in the reservoir to quickly fill the pressure chamber when needed. \\
-And the pressure chamber is what actually raises the engine valves.
 ====== Oil System Modifications and Trade-Offs ======
@@ Line 1262: / Line 1163: @@
 Either of these, done properly, will effectively block the discharge from happening. \\
-{{:techtalk:ref:oil:86-90_oil_filter_pad_mod_3_by_joergen.jpg?direct&300|}} ((photo by Jorgen of the XLFORUM http://xlforum.net/forums/showthread.php?t=1619616&highlight=jorgen+oil+pump&page=42)) \\
+{{:techtalk:ref:oil:86-90_oil_filter_pad_mod_3_by_joergen.jpg?direct&300|}} ((photo by Jorgen of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-engine-conversions/149281-124-1993-xlh-build-thread/page42?t=1619616&highlight=jorgen+oil+pump&page=42)) \\
 So what is the trade-off of doing this mod? \\

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