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techtalk:ref:engmech04 [2019/06/06 02:43]
hippysmack [Aftermarket Breathers / PVC Valves]
techtalk:ref:engmech04 [2019/06/19 03:03] (current)
hippysmack [Vacuum Pressure]
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 CC pressure both pushes to and sucks from the breather valve. \\ CC pressure both pushes to and sucks from the breather valve. \\
 So testing CC pressure with a PSI gauge would probably just destroy it. \\ So testing CC pressure with a PSI gauge would probably just destroy it. \\
 +
 +====== Symptoms of High Crankcase Pressure ======
 +Picture a balloon inside the engine being blown up. \\
 +It puts internal pressure against the weakest structural points (gaskets and seals). \\
 +
 +Symptoms include: ((Jorgen of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=75740&​highlight=reed+valve&​page=9)) \\
 +Sweating oil from the cylinder base gaskets and rocker boxes. \\
 +As well as the push rod tubes and lifter blocs on the other side. \\
 +
 +====== Vacuum Pressure ======
 +**PSIG** - (pounds per square inch (gauge): ((https://​www.setra.com/​blog/​vacuum-pressure-what-is-it-how-do-you-measure-it)) \\
 +Gauge pressure is pressure measured relative to ambient atmospheric pressure (approximately 14.7 PSIA). \\
 +**PSIA** - pounds per square inch (absolute): \\
 +Absolute pressure is measured relative to high vacuum (0 PSIA). \\
 +**PSIV** - pounds per square inch (vacuum): \\
 +Vacuum pressure is measured relative to ambient atmospheric pressure. \\
 +**PSID** - pounds per square inch (differential):​ \\
 +Differential pressure is pressure measured relative to a reference pressure. \\
 +If the reference pressure is one atmosphere the differential pressure range is equal to gauge pressure range. \\
 +
 +The earth'​s atmosphere exerts a pressure upon us, known as the atmospheric pressure, which can be measured in a number of ways. ((https://​www.dekkervacuum.com/​resource-library/​knowledge-database/​technical-data/​what-is-vacuum/​)) \\
 +__At sea level__, the standard pressure is 14.7 psia or 29.92" of mercury (Hg) or 760 mm of mercury (Torr). \\
 +Because the barometric pressure varies, the above "sea level" pressures are used as a reference point. \\
 +There is 14.7 psia pressure being exerted on us by the atmosphere, but there is also 14.7 psia inside of us pushing out. \\
 +(given the fact that for every action there is an equal but opposite reaction) \\
 +Thus, we do not feel discomfort from the atmospheric pressure. \\
 +Another way to state this is that there is no differential pressure between the inside and outside of our bodies.
 +
 +The term "​vacuum"​ is used to describe the zone of pressure below atmospheric pressure. \\
 +Vacuum is a negative gauge pressure, usually referenced to the existing standard barometric pressure where the equipment will operate. \\
 +This means vacuum is a differential reading between the surrounding atmospheric pressure and the pressure in the system evacuated. \\
 +In all instances when given a vacuum condition, the question should be asked, at what elevation the pump will operate. \\
 +(since the barometric pressure varies with altitude above or below sea level) \\ \\
 +Example of differential pressures (or Vacuum):
 +{{:​techtalk:​ref:​engmech:​differential_pressure_drawing_1_by_hippysmack.jpg?​direct&​450|}} ((drawing by Hippysmack))
 +
 +Applying the same principles, you can see the relation of positive and negative crankcase pressure in the Sportster engine. \\
 +Every piston upstroke and downstroke reverses crankcase pressure from positive to negative forces. \\
 +The pistons act as an air pump and then a suction pump respectively. \\
 +Below are drawings exampling positive and negative (vacuum) forces inside the engine. \\
 +
 +91-03 models with head breather vents: \\
 +{{:​techtalk:​ref:​engmech:​91-03_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​ref:​engmech:​91-03_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack))
 +
 +04 and Up models with head breather vents: \\
 +{{:​techtalk:​ref:​engmech:​04_and_up_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​ref:​engmech:​04_and_up_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack))
 +
 ====== Blowby ====== ====== Blowby ======
 Blowby pertains to the condition of ring seal at the cylinders / pistons. \\ Blowby pertains to the condition of ring seal at the cylinders / pistons. \\
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 Regarding blowby at high revs, the key factor is ‘ring-flutter’ or ‘ring-seal’. ((bunny32 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=67658&​page=6)) \\ Regarding blowby at high revs, the key factor is ‘ring-flutter’ or ‘ring-seal’. ((bunny32 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=67658&​page=6)) \\
 Starting with a dead cold engine, there’s no blow-by measurable for a time after start-up. \\ Starting with a dead cold engine, there’s no blow-by measurable for a time after start-up. \\
-Then at warm idle, it starts. Above idle it either drops off or holds constant, as revs go up. Ring seal improves above idle...........+Then at warm idle, it starts. Above idle it either drops off or holds constant, as revs go up. \\ 
 +Ring seal improves above idle. \\
 As you get near peak revs, ring-seal again fails and gusts of blow-by pass down into the crankcase. \\ As you get near peak revs, ring-seal again fails and gusts of blow-by pass down into the crankcase. \\
 ==== Ring construction ==== ==== Ring construction ====
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 ==== Testing ring seal ==== ==== Testing ring seal ====
-A leak down test is the best way to check ring seal. \\+A leak down test is the best way to check ring seal. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=110375&​highlight=variable+volume#​post110375)) ​\\
 The tester is not expensive and it's handy as hell. \\ The tester is not expensive and it's handy as hell. \\
 Listen for where the air is coming out during the test: intake port, exhaust port, or breathers. \\ Listen for where the air is coming out during the test: intake port, exhaust port, or breathers. \\
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 ====== Engine Venting ====== ====== Engine Venting ======
 +See also [[techtalk:​evo:​engmech07|Evo Crankcase Ventilation]] in the Sportsterpedia. \\
  
 To keep the engine from pulling in air from the outside, HD fits the breather vent(s) with a check valve. \\ To keep the engine from pulling in air from the outside, HD fits the breather vent(s) with a check valve. \\
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 |{{:​techtalk:​ref:​engmech:​mercedes_benz_pcv_valve_by_electronbee.jpg?​direct&​300|}}| |{{:​techtalk:​ref:​engmech:​mercedes_benz_pcv_valve_by_electronbee.jpg?​direct&​300|}}|
  
 +From aswracing on testing breather vents for HP gain: ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=75740&​highlight=reed+valve&​page=6)) \\
 +<​blockquote>​Many years ago, I spent most of a day dyno testing breather check valves. \\
 +I was writing for Battle2win magazine at the time and published my findings there. \\
 +The bottom line was that none of them added a single iota of measurable horsepower, despite the grandiose claims of up to 7% from the manufacturers. \\
 +The only thing I could get to show up on the dyno at all was the removal of the blowby from the intake tract.\\
 +You can read all about the results here.
 +One of the companies involved, ET products (maker of the Spyke Krank vent) took exception. \\
 +I very carefully retested using their suggestions,​ but I got the exact same answer. \\
 +</​blockquote>​
 ====== Why Oil Pukes Out the Breather Vent ====== ====== Why Oil Pukes Out the Breather Vent ======
 The real reason these things like to spit oil out the breather is because they'​re a common crankpin 45° design. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=110375&​highlight=variable+volume#​post110375)) \\ The real reason these things like to spit oil out the breather is because they'​re a common crankpin 45° design. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=110375&​highlight=variable+volume#​post110375)) \\
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 ====== Engine Venting Mods ====== ====== Engine Venting Mods ======
 +See also [[techtalk:​ref:​oil05|Engine and Primary Oil System Modifications]] for a listing of mods from the XLFORUM. \\
 +
 +Engine breathers control when CC pressure exits the engine. \\
 +So when you're discussing engine breathing mods, you're also discussing changing crankcase pressure. \\
 +Revised crankcase breathing is an area where you have huge potential to create unintended consequences. ((maru of theXLFORUM http://​xlforum.net/​forums/​showthread.php?​t=75740&​highlight=reed+valve&​page=6)) \\
 +Few really understand the ifs, ands and buts of all the factors the factory took into consideration when they designed the system. \\
 +
 The stock vent system doesn'​t keep up with the increased pressures and volume of air from modified engines very well. \\ The stock vent system doesn'​t keep up with the increased pressures and volume of air from modified engines very well. \\
 The MoCo somehow balanced the engine design factors to come up with a compromise that worked. \\ The MoCo somehow balanced the engine design factors to come up with a compromise that worked. \\
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 Wetsumping during shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing. \\  Wetsumping during shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing. \\ 
  
-Wetsumping (at high RPM) is a condition when the oil pump isn't removing the oil as fast as it's feeding it. \\+Wetsumping (at sustained ​high RPM) is a condition when the oil pump isn't removing the oil as fast as it's feeding it. \\
 If the cam box fills with oil, it comes out the breather and right to your air cleaner. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=110375&​highlight=variable+volume#​post110375)) \\ If the cam box fills with oil, it comes out the breather and right to your air cleaner. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=110375&​highlight=variable+volume#​post110375)) \\
 It's been a chronic issue on XL's for years, happens on the 5-speed bikes as well as the 4-speeds and the ironheads. \\ It's been a chronic issue on XL's for years, happens on the 5-speed bikes as well as the 4-speeds and the ironheads. \\
 But often on the head breather models (91-up), you never know like you do on earlier bikes with the breather on the cam box (pre 91). \\ But often on the head breather models (91-up), you never know like you do on earlier bikes with the breather on the cam box (pre 91). \\
  
-The oil pump was updated in '98 and then in '07 and you rarely see this anymore. \\+The oil pump was updated in '98 and then in '07 and you rarely see this anymore ​(while putting around town). \\
 But it still happens on high rpm race motors from time to time. \\ But it still happens on high rpm race motors from time to time. \\
 It's always the best sealed motors that have the issue, especially gapless ring motors. \\ It's always the best sealed motors that have the issue, especially gapless ring motors. \\
 Vacuum (45° configuration as mentioned above) in the crankcase interferes big time with scavenging. \\ Vacuum (45° configuration as mentioned above) in the crankcase interferes big time with scavenging. \\
 The 98-up style pump can be fitted to the older bikes (they'​ve even been fitted to ironheads). \\ The 98-up style pump can be fitted to the older bikes (they'​ve even been fitted to ironheads). \\
 +
 +The late model bikes can easily wet sump if ridden aggressively on the street, however. ((maru of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=75740&​highlight=reed+valve&​page=7)) \\
 +And they'​ve been known to wet sump with only 3 back to back dyno pulls. \\
 +The results are dramatic when it happens. It is not anything like a barely noticeable loss in performance. \\
 +The scavenging gets behind to some degree in a single drag strip run. \\
  
 Beyond that, about all you can do is lower the oil pressure. \\ Beyond that, about all you can do is lower the oil pressure. \\
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 This mod will send a small amount of pressure side oil back to the tank instead of into the engine. \\ This mod will send a small amount of pressure side oil back to the tank instead of into the engine. \\
  
 +====== Bad Ring Seal vs Wet sumping ======
 +Wet sumping and oil spatters from the crankcase are two different things. ((Jorgen of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=75740&​highlight=reed+valve&​page=7)) \\
 +Daily driver owners with oily air cleaners can get these two ideas confused. \\
 +
 +Bad ring seal helps evaquate the sump from oil. \\
 +But on the other hand, it increases the flow rate through the crank vent system to such levels that a lot of oil droplets join in. \\
 +Apart from leaking cylinder base gaskets and push rod tubes, large blowby and high crank pressure also contributes to even larger ring leakage. \\
 +It's a vicious circle. \\
  
 +Sometimes owners who struggle with an oily air cleaner problem seem more concerned with wet sumping. \\
 +When they should concentrate in evaluating and improving ring seal. \\
 +And ideally also route the crankcase breather lines to a catch tank instead of the A/C. \\
 +Re-routing the vent(s) from the breather to a catchtank has many advantages. \\
 +Not least it is a powerful tool to monitor the state of the engine. \\
 +There should be more water than oil in the catch tank. \\
 +At least if air temp is 20C or below. \\
 ====== Engine Breathing ====== ====== Engine Breathing ======