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techtalk:ref:engmech04 [2019/06/06 02:41] hippysmack [Aftermarket Breathers / PVC Valves] |
techtalk:ref:engmech04 [2019/06/20 22:46] hippysmack [Crankcase 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. \\ | ||
+ | |||
+ | ====== Affects of the 45° Rod / Piston Arrangement ====== | ||
+ | Piston / rod positions are relative to positive or negative pressure in the crankcase. | ||
+ | Forget about valve opening for a second. | ||
+ | |||
+ | - With the piston up, | ||
+ | * The top of the piston is not pulling vacuum in the cylinder. | ||
+ | * The crankcase is pulling vacuum. | ||
+ | - With the piston down, | ||
+ | * The piston is pulling vacuum in the cylinder. | ||
+ | * The crankcase is exerting positive pressure. | ||
+ | |||
+ | These two conditions create what we call crankcase pressure. \\ | ||
+ | How crankcase pressure moves inside the engine does or doesn't help during wet sumping. | ||
+ | |||
+ | Intake vacuum is relative to piston / rod positions. \\ | ||
+ | On carbed models with VOES / MAP: \\ | ||
+ | Vacuum is created in the cylinders which pulls vacuum from the carb. \\ | ||
+ | This vacuum is tapped into and used to operate ignition timing through the VOES / Map. \\ | ||
+ | So a vacuum gauge plugged into the vacuum line at the carb does reflect the position of the two pistons. \\ | ||
+ | I.E. the gauge moves when the pistons are on the way down and goes toward the resting position when the pistons are coming up. \\ | ||
+ | (of course, you'd then have to take in accountancy if the intake or exhaust valve was open at the time) \\ | ||
+ | |||
+ | Some time and tune older V-8s with a vacuum gauge instead of a timing light. \\ | ||
+ | For each piston going up, there is a piston going down. \\ | ||
+ | Intake vacuum stays (more) constant in the middle of the push / pull. \\ | ||
+ | A vacuum gauge shows a more steady dynamic condition. \\ | ||
+ | Likewise are the forces in the crankcase (crankcase pressure). \\ | ||
+ | |||
+ | The rods \ piston action in the Sportster engine are close together (45° apart). \\ | ||
+ | There are 360° around the flywheels. \\ | ||
+ | If the rods were 180° apart instead, one piston would be going up at the same time the other is going down. \\ | ||
+ | Just as in a V-8, crankcase pressure would be more equalized between them. \\ | ||
+ | |||
+ | Since Sportster piston movement is not equalized, we get the potato, potato sound we all love but the equilibrium in the crankcase is off by design. \\ | ||
+ | Take the PCV off the valve cover on the V-8 while running and it just smokes a little. \\ | ||
+ | Take the breather valve off the Sportster and oil pukes out. \\ | ||
+ | |||
+ | Likewise, a vacuum gauge on the carb line will be erratic and not a useful test. | ||
+ | Hook up a vacuum gauge to it and the gauge bounces from vacuum to no vacuum pretty wildly. | ||
+ | Crankcase pressure is doing the same thing. \\ | ||
+ | |||
+ | |||
+ | ====== 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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* Mercedes Benz P/N# 271-018-00-29 ~$13. | * Mercedes Benz P/N# 271-018-00-29 ~$13. | ||
* Reed type PCV valve. Fast acting. Used for their C 230 Kompressor engine. | * Reed type PCV valve. Fast acting. Used for their C 230 Kompressor engine. | ||
+ | * Dims: 2-1/2" long by 1-1/8" with an I.D of 1/4". | ||
* McCaster Carr P/N# 4610K17 ~$6. | * McCaster Carr P/N# 4610K17 ~$6. | ||
* Umbrella valve. Vacuum check valve. | * Umbrella valve. Vacuum 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 ====== | ||