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techtalk:ref:engmech07 [2020/10/09 01:33] hippysmack [1977-1985] |
techtalk:ref:engmech07 [2023/12/26 18:01] hippysmack |
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| ====== Engine Breathing ====== | ====== Engine Breathing ====== | ||
| - | + | 1957-1976 engines have a different breathing cycle than 1977-up engines. The end result is the same. However, the means to get there is different. \\ | |
| - | 57-76 engines have a different breathing cycle than 77-up engines. The end result is the same. However, the means to get there is different. \\ | + | |
| Below are the two systems explained. \\ | Below are the two systems explained. \\ | ||
| You can also reference the sub documents under each particle subject heading. These pages are more detailed information on certain subjects. \\ | You can also reference the sub documents under each particle subject heading. These pages are more detailed information on certain subjects. \\ | ||
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| * [[techtalk:ref:engmech07l|How Piston Swept Volume Compares When the Breather Opens as to When It Closes]] | * [[techtalk:ref:engmech07l|How Piston Swept Volume Compares When the Breather Opens as to When It Closes]] | ||
| - | <blockquote>The shallow sump, timed breather system, comes from the aviation world of old. ((mrmom9r of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854&page=4)) \\ | + | <blockquote>The shallow sump, timed breather system, comes from the aviation world of old. ((mrmom9r of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/122424-breather-diagrams/page4?t=1204854&page=4)) \\ |
| Piston driven aircraft had to be able to evacuate the oil from the crankcase regardless of engine altitude and that system does that. \\ | Piston driven aircraft had to be able to evacuate the oil from the crankcase regardless of engine altitude and that system does that. \\ | ||
| At the time Harley adapted that system they were copying the highest engine technology of the day. \\ | At the time Harley adapted that system they were copying the highest engine technology of the day. \\ | ||
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| The oil is separated from the air by way of collision. Everything the air/oil mix touches on the way to the vent separates some oil from the air. | The oil is separated from the air by way of collision. Everything the air/oil mix touches on the way to the vent separates some oil from the air. | ||
| - | 57-76 engines breath and scavenge oil from the same hole. \\ | + | 1957-1976 engines breath and scavenge oil from the same hole. \\ |
| On piston down stroke, drain oil is pushed into the oil galley (slot) in the rear of the crankcase and toward the oil trap beside the breather gear. \\ | On piston down stroke, drain oil is pushed into the oil galley (slot) in the rear of the crankcase and toward the oil trap beside the breather gear. \\ | ||
| - | When the breather window opens, both drain oil and crankcase air pressure are pushed into the rotating breather gear. \\ | + | When the breather window opens after downstroke, both drain oil and crankcase air pressure are pushed into the rotating breather gear. \\ |
| The oil and air is slung out from the center of the gear into the gearcase where it bounces on cam gears, case walls, etc. \\ | The oil and air is slung out from the center of the gear into the gearcase where it bounces on cam gears, case walls, etc. \\ | ||
| Air / oil mist flows toward the vent and the oil gets spun out of suspension by the oil slinger on the generator drive gear. \\ | Air / oil mist flows toward the vent and the oil gets spun out of suspension by the oil slinger on the generator drive gear. \\ | ||
| Crankcase exhaust air is then sent out the breather tube. \\ | Crankcase exhaust air is then sent out the breather tube. \\ | ||
| - | The breather valve then closes on piston upstroke past BDC, creating vacuum in the crankcase and the cycle repeats. \\ | + | The breather valve then closes on after the pistons rise (after BDC), creating vacuum in the crankcase and the cycle repeats. \\ |
| ===== 1977-1985 ===== | ===== 1977-1985 ===== | ||
| - | |||
| The one way breather style system is more like a car PCV system. ((mrmom9r of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854&page=4)) Unlike an auto PCV, a Sportster has a faster acting type one way valve. \\ | The one way breather style system is more like a car PCV system. ((mrmom9r of the XLFORUM http://xlforum.net/forums/showthread.php?t=1204854&page=4)) Unlike an auto PCV, a Sportster has a faster acting type one way valve. \\ | ||
| A deep (dry) sump was added to 77> casings and the scavenge side of the oil pump pulls the oil from the scavenge port in the rear of the sump area. \\ | A deep (dry) sump was added to 77> casings and the scavenge side of the oil pump pulls the oil from the scavenge port in the rear of the sump area. \\ | ||
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| There were several changes made of the valve itself, but they operate on the same principle as a one way breather valve. \\ | There were several changes made of the valve itself, but they operate on the same principle as a one way breather valve. \\ | ||
| + | ==== OEM oil paths and engine breathing drawings ==== | ||
| + | |||
| + | {{:techtalk:ref:engmech:1957-1971_sportster_crankcase_pressure_path_by_hippysmack.png?direct&500|}} ((drawing by Hippysmack)) \\ | ||
| + | |||
| + | {{:techtalk:ref:engmech:1972-1976_sportster_crankcase_pressure_path_by_hippysmack.png?direct&750|}} ((drawing by Hippysmack)) \\ | ||
| + | {{:techtalk:ref:engmech:1977-1985_sportster_crankcase_pressure_path_by_hippysmack.png?direct&500|}} ((drawing by Hippysmack)) \\ | ||
| ====== Engine Breather Valves ====== | ====== Engine Breather Valves ====== | ||
| ===== Sub Documents ===== | ===== Sub Documents ===== | ||
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| * [[techtalk:ref:engmech07h|Oil Drainback and Supplemental Air Intake from Breather Valves]] | * [[techtalk:ref:engmech07h|Oil Drainback and Supplemental Air Intake from Breather Valves]] | ||
| * [[techtalk:ref:engmech07i|Dissecting the 77-78 Breather (foo-foo) Valve (24634-77)]] | * [[techtalk:ref:engmech07i|Dissecting the 77-78 Breather (foo-foo) Valve (24634-77)]] | ||
| + | * [[techtalk:ref:engmech07j|Further Study of the 79-E82 Reed Valve]] | ||
| * [[techtalk:ref:engmech07s|XR-750 8-Ball Breather Valve]] | * [[techtalk:ref:engmech07s|XR-750 8-Ball Breather Valve]] | ||
| * [[techtalk:ref:engmech05|Breather Venting / Relocation]] (list of breathing mods and aftermarket breathers for 1977-up engines) | * [[techtalk:ref:engmech05|Breather Venting / Relocation]] (list of breathing mods and aftermarket breathers for 1977-up engines) | ||
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| * [[techtalk:ref:engmech07b|Affects of the 45° Rod / Piston Arrangement]] | * [[techtalk:ref:engmech07b|Affects of the 45° Rod / Piston Arrangement]] | ||
| * [[techtalk:ref:engmech07c|Differential Pressure]] | * [[techtalk:ref:engmech07c|Differential Pressure]] | ||
| + | * [[techtalk:ref:engmech04r|Air Pressure and Vacuum at Different Elevations]] | ||
| * [[techtalk:ref:engmech07d|Blowby and Ring Seal]] | * [[techtalk:ref:engmech07d|Blowby and Ring Seal]] | ||
| * [[techtalk:ref:engmech07f|Liquid Drag vs Fluid Drag]] | * [[techtalk:ref:engmech07f|Liquid Drag vs Fluid Drag]] | ||
| Line 116: | Line 122: | ||
| * [[techtalk:ref:oil20|Oil Tank Pressure]] | * [[techtalk:ref:oil20|Oil Tank Pressure]] | ||
| * [[techtalk:ref:engmech04p|Vacuum Pump for Reducing Crankcase Pressure]] | * [[techtalk:ref:engmech04p|Vacuum Pump for Reducing Crankcase Pressure]] | ||
| + | * See also in the Sportsterpedia: | ||
| + | * [[techtalk:ih:oil01#transfer_valve_76_and_earlier|Transfer Valve]] | ||
| ==== In the crankcase air system ==== | ==== In the crankcase air system ==== | ||
