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techtalk:ref:engmech04 [2020/10/06 19:19] hippysmack [Engine breathing mods in general] |
techtalk:ref:engmech04 [2020/10/08 16:59] hippysmack [Sub Documents] |
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| ====== Evo Crankcase Pressure and Engine Breathing ====== | ====== Evo Crankcase Pressure and Engine Breathing ====== | ||
| - | See also in the REF section of the Sportsterpedia: \\ | + | \\ |
| - | * [[techtalk:ref:oil10#refoiling_lubrication|Wet Sumping]] | + | |
| - | * [[techtalk:ref:oil05#engine_and_primary_oil_system_modifications|Engine and Primary Oil System Modifications]] | + | |
| ====== Engine Breathing ====== | ====== Engine Breathing ====== | ||
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| At that point, the tiny hole is a slight air (atmosphere) intake hole. \\ | At that point, the tiny hole is a slight air (atmosphere) intake hole. \\ | ||
| - | The crankcase air pushes past each breather valve and exits through the heads. \\ | + | The crankcase air pushes past the breather valve and exits the engine out the breather vent (which is factory plumbed into the air cleaner backing plate). \\ |
| - | A hole in each head connects the path from the outlet of the breather vent to atmosphere. \\ | + | |
| - | A hollow bolt installed into each head passes the air into the air cleaner backing plate. \\ | + | {{:techtalk:evo:engmech:86-90_cc_pressure_drawing_by_hippysmack.jpg?direct&300|}} ((drawing by Hippysmack)) {{:techtalk:evo:engmech:86-90_engine_crankcase_breathing_by_hippysmack.jpg?direct&300|}} ((drawing by Hippysmack)) |
| ==== 1991-2003 Engine Specifics ==== | ==== 1991-2003 Engine Specifics ==== | ||
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| At that point, the tiny hole is a slight air (atmosphere) intake hole. \\ | At that point, the tiny hole is a slight air (atmosphere) intake hole. \\ | ||
| - | The crankcase air pushes past each breather valve and exits the engine out the breather vent (which is factory plumbed into the air cleaner backing plate). \\ | + | The crankcase air pushes past each breather valve and exits through the heads. \\ |
| + | A hole in each head connects the path from the outlet of the breather vent to atmosphere. \\ | ||
| + | A hollow bolt installed into each head passes the air into the air cleaner backing plate. \\ | ||
| + | |||
| + | {{:techtalk:evo:engmech:91_and_up_cc_pressure_drawing_by_hippysmack.jpg?direct&300|}} ((drawing by Hippysmack)) {{:techtalk:evo:engmech:91-up_engine_crankcase_breathing_by_hippysmack.jpg?direct&300|}} ((drawing by Hippysmack)) | ||
| ==== 2004-Up Engine Specifics ==== | ==== 2004-Up Engine Specifics ==== | ||
| Line 102: | Line 106: | ||
| A hole in each head connects the path from the outlet of the breather vent to atmosphere. \\ | A hole in each head connects the path from the outlet of the breather vent to atmosphere. \\ | ||
| A hollow bolt installed into each head passes the air into the air cleaner backing plate. \\ | A hollow bolt installed into each head passes the air into the air cleaner backing plate. \\ | ||
| - | | + | |
| + | {{:techtalk:evo:engmech:91_and_up_cc_pressure_drawing_by_hippysmack.jpg?direct&300|}} ((drawing by Hippysmack)) {{:techtalk:evo:engmech:91-up_engine_crankcase_breathing_by_hippysmack.jpg?direct&300|}} ((drawing by Hippysmack)) | ||
| ==== OEM oil paths and engine breathing drawings ==== | ==== OEM oil paths and engine breathing drawings ==== | ||
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| ===== Sub Documents ===== | ===== Sub Documents ===== | ||
| * [[techtalk:ref:engmech04k|Breather Valves (1957-Up)]] (list of breather valve changes) | * [[techtalk:ref:engmech04k|Breather Valves (1957-Up)]] (list of breather valve changes) | ||
| + | * [[techtalk:ref:engmech04j|Further Study of Evo Sportster Breather Valves]] | ||
| + | * [[techtalk:ref:engmech07h|Oil Drainback and Supplemental Air Intake from Breather Valves]] | ||
| * [[techtalk:ref:engmech05|Breather Venting / Relocation]] (list of breathing mods and aftermarket breathers) | * [[techtalk:ref:engmech05|Breather Venting / Relocation]] (list of breathing mods and aftermarket breathers) | ||
| * [[techtalk:ref:engmech04l|Head Vents vs Cam Chest Vent]] | * [[techtalk:ref:engmech04l|Head Vents vs Cam Chest Vent]] | ||
| + | * [[techtalk:ref:oil10#refoiling_lubrication|Wet Sumping]] | ||
| * [[techtalk:ref:engmech04m|Why Oil Pukes Out the Breather]] | * [[techtalk:ref:engmech04m|Why Oil Pukes Out the Breather]] | ||
| - | ==== Symptoms of Breather problems ==== | + | ==== Symptoms of Breather Valve Problems ==== |
| - | **The most noticeable signs of breather valve problems are weeping gaskets or oil excessively leaking out the breather or puking oil out of it**. \\ | + | **The most notable signs of breather valve problems include weeping / leaking gaskets or blown gaskets / seals**. \\ |
| - | When the umbrella(s) gets hard, it doesn't flex well to allow the engine to breath out on exhale. \\ | + | L82-up rubber umbrella(s) get hard and if they don't flex well enough, they'll allow the engine to fully inhaler and exhale on every stroke uncontrolled. \\ |
| - | Then the trapped in air is compounded on the next stroke. The excess air contributes to more vacuum created and implodes the gaskets. \\ | + | Stopped up breather valves won't allow the engine to breath well and can create excess vacuum and implode gaskets. \\ |
| Or it contributes to too high of oil density and slings excess oil out. Other factors are involved so results will vary. \\ | Or it contributes to too high of oil density and slings excess oil out. Other factors are involved so results will vary. \\ | ||
| + | However, a slight amount of oil in mist form coming out the vent/air cleaner is totally normal and does not quantify as puking oil. \\ | ||
| - | **Wetsumping during shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing**. \\ | + | **Wetsumping can be a result of poor engine breathing but not always**. \\ |
| - | [[techtalk:ref:oil10#wet_sumping|Click here]] to read the full article on wetsumping in the REF section of the Sportsterpedia. \\ | + | Blowing oil out after extended shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing. \\ |
| - | + | Blowing oil out the vent/air cleaner during riding first looks to the oil tank being overfilled. \\ | |
| - | The foregoing addresses the affects of wetsumping upon with the engine running. \\ | + | If the engine is not at operating temp before checking the oil level, you'll end up adding too much oil to the system. \\ |
| - | Later engines are not competition engines. Maybe the earlier Sportsters were, but those days are long gone. ((chevelle of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854&page=3)) \\ | + | Blowing oil out the vent/aircleaner during high sustained RPM may be high crankcase pressure or poor oil scavenging. \\ |
| - | + | Also see the full article on wetsumping in the sub documents above. \\ | |
| - | **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)) \\ | + | |
| - | 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). \\ | + | |
| - | * Wetsumping can also be attributed to the //Density// of the air / oil mix in the crankcase. ((Dr Dick of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854)) | + | |
| - | * The higher the density (//not volume//) of the fluid (air / oil mix), the more it drags on the rotating parts it contacts. | + | |
| - | * As the density increases so does the fluid drag it imposes on the rotating parts (read flywheel assembly). | + | |
| - | * This drag robs power. That's why we mess with it, to reduce the power loss. | + | |
| - | * Example: If they are the same size (volume), what takes less power? | + | |
| - | * Stirring a cup of coffee or stirring a coffee milkshake? It's the one that's less dense. | + | |
| - | * So now we know that less drag = more horsepower and the air is the medium that gets the oil out of the cases. \\ The 'leaner' (less oil in the air), the less the drag (air / oil is less dense). ((Dr Dick of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854&page=2)) | + | |
| - | + | ||
| - | 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 and race motors from time to time. \\ | + | |
| - | 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. \\ | + | |
| - | 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. \\ | + | |
| - | But don't go down that path unless you establish for sure you are wetsumping and other measures won't fix the situation. \\ | + | |
| - | Read more here on a [[techtalk:ref:oil05a|Homemade Oil System Bypass]] for reducing the oil pressure in the REF section of the Sportsterpedia. \\ | + | |
| - | This mod will send a small amount of pressure side oil back to the tank instead of into the engine. \\ | + | |
| - | + | ||
| ====== Crankcase Pressure ====== | ====== Crankcase Pressure ====== | ||
