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techtalk:ref:tools173 [2020/10/25 03:28] – [What is a manometer?] hippysmacktechtalk:ref:tools173 [2024/01/24 23:12] (current) – hippysmack
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   * [[techtalk:ref:genmsr04#using_diagnosing_with_a_slack_tube_manometer|Using / Diagnosing with a Slack Tube (Manometer)]]   * [[techtalk:ref:genmsr04#using_diagnosing_with_a_slack_tube_manometer|Using / Diagnosing with a Slack Tube (Manometer)]]
   * [[techtalk:ref:engmech04g|Slack Tube Testing on a 1998 1250S Sportster]]   * [[techtalk:ref:engmech04g|Slack Tube Testing on a 1998 1250S Sportster]]
 +  * [[techtalk:ref:engmech07p|Testing with a Slack Tube (Manometer) by bustert]]
  
 A manometer is used to measure the pressure difference between two gases, often atmosphere and the gas being tested. ((https://sciencing.com/perform-manometer-test-7644846.html)) \\ A manometer is used to measure the pressure difference between two gases, often atmosphere and the gas being tested. ((https://sciencing.com/perform-manometer-test-7644846.html)) \\
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 The difference in the height of the liquid in each side is used to calculate the source pressure. \\ The difference in the height of the liquid in each side is used to calculate the source pressure. \\
  
 +===== What is it used for? =====
 +There are many purposes for a manometer in diagnosing Motorcycle issues; \\
 +  * A manometer has long been a tool to help in synchronizing the vacuum between multi-carb engines. \\ With a Sportster having only the one carb, the meter can still be used to measure how much vacuum is present in the venture.
 +  * Measuring crankcase pressure
 +  * Measuring breather vent(s) opening pressure
 +  * Measuring primary compartment pressure
 +  * Flow bench testing on heads
 +  * Calibrating pressure gauges
  
 ===== Where to get one ===== ===== Where to get one =====
- +A simple U-tube manometer can be homemade or bought commercially. \\
-A simple U-tube manometer can be homemade made or bought commercially. \\+
 Dwyer is a popular brand and these can also be purchased used (Ebay) at a lower price. \\ Dwyer is a popular brand and these can also be purchased used (Ebay) at a lower price. \\
 Most of the Dwyer tubes have some check valves in the plastic block up top that are supposed to keep them from loosing liquid if the draft changes suddenly. ((https://www.hearth.com/talk/threads/dwyer-manometer-use-help.91591/)) \\ Most of the Dwyer tubes have some check valves in the plastic block up top that are supposed to keep them from loosing liquid if the draft changes suddenly. ((https://www.hearth.com/talk/threads/dwyer-manometer-use-help.91591/)) \\
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 Many folks strip out the valves and drain the tubes when they are not using them. \\ Many folks strip out the valves and drain the tubes when they are not using them. \\
 The difference in elevation between the two liquid levels is the draft. \\ The difference in elevation between the two liquid levels is the draft. \\
-|This is the Dwyer manometer.((photo by bustert of the XLFORUM http://xlforum.net/forums/showthread.php?p=5767694#post5767694))|Homemade version using a ruler as a scale. ((photo by Hippysmack of the XLFORUM http://xlforum.net/forums/showthread.php?p=5784790#post5784790))|+|This is the Dwyer manometer.((photo by bustert of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-bottom-end/197307-sportster-crankcase-pressure-engine-breathing-wetsumping-and-mods/page31#post4326111))|Homemade version using a ruler as a scale. ((photo by Hippysmack of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-bottom-end/197307-sportster-crankcase-pressure-engine-breathing-wetsumping-and-mods/page52#post4349847))|
 |{{:techtalk:ref:engmech:checking_cc_pressure_at_timing_hole_plug_5_by_bustert.jpg?direct&300|}}| {{:techtalk:ref:engmech:homemade_slack_tube_5_by_hippysmack.jpg?direct&300|}}| |{{:techtalk:ref:engmech:checking_cc_pressure_at_timing_hole_plug_5_by_bustert.jpg?direct&300|}}| {{:techtalk:ref:engmech:homemade_slack_tube_5_by_hippysmack.jpg?direct&300|}}|
  
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 The levels of the fluid in the two vertical columns should be equal at this point, as they are currently exposed to the same pressure. \\ The levels of the fluid in the two vertical columns should be equal at this point, as they are currently exposed to the same pressure. \\
 This level is therefore marked and identified as the zero reference point of the manometer. \\ This level is therefore marked and identified as the zero reference point of the manometer. \\
- 
-===== What is it used for? ===== 
- 
-There are many purposes for a manometer in diagnosing Motorcycle issues; \\ 
-  * A manometer has long been a tool to help in synchronizing the vacuum between multi-carb engines. \\ With a Sportster having only the one carb, the meter can still be used to measure how much vacuum is present in the venture. 
-  * Measuring crankcase pressure 
-  * Measuring breather vent(s) opening pressure 
-  * Measuring primary compartment pressure 
-  * Flow bench testing on heads 
-  * Calibrating pressure gauges 
- 
-===== How tall should the tubes be? ===== 
-Generally, whichever liquid media you are using, you want the meter to be tall enough so the liquid doesn't suck back into the engine. \\ 
-The length of the tubes needs to be longer than the expected pressure you'll be measuring. Make sure to account for spokes in considering the tube lengths. \\ 
-The standard conversion from PSI to Inches of Water: 1 PSI is equal to 28" of water column (overall vertical movement). \\ 
-When using a U-tube type manometer, divide the total inches of water travel (in both legs) by 2 as the water in each leg of the instrument are moving. \\ 
-I.E., 1" down on one leg and 1" up on the other equals a total of 2" of total movement. \\ 
-Therefore, 1 PSI = 28" of water divided by 2 = 14" of movement per leg per pound of pressure. \\ 
- 
-  * **Example: To convert 4 PSI to total inches of water**: 
-    * 1 PSI = 28" of water 
-    * 2 psi = 56" of water (2 x 28 = 56) 
-  * **Likewise: To convert total inches of water to PSI**: 
-    * 56" of total water = 2 PSI (56 / 28) 
- 
-So, technically, a 30" tall U-Tube instrument (each leg 30" tall) would do for testing from 2 PSI and below readings. \\ 
-However, a 36" tall instrument may account for pressure spikes better without dumping water out the end or sucking water into the engine. \\ 
-**Caution**: \\ 
-Once the water reaches the top of the tube or drops below the top of the "U" (crossover) the water will dump out the end of the tube. \\ 
-(in testing on a Sportster engine, generally this means the water getting sucked into the engine) \\  
- 
-If need be, you can get away with using a shorter tube by using a valve to throttle back the source pressure. \\ 
-In measuring crankcase pressure; \\ 
-You want the vertical leg to be able to the hold the actual pressure differential of water plus an airspace above that. \\ 
-Else, you could suck the liquid into the engine. \\ 
-We know of two Sportsters on the XLForum that have been tested for crankcase pressure using a slack tube. \\ 
-At idle, 15" of water column has been logged on one leg. \\ 
-However, the variables are specific to each individual rig. \\ 
-The water level is usually filled to the center of the tubes to allow equal sway up and down the range, but especially the vacuum leg. \\ 
-Depending on the individual engine, your readings may be higher or lower but a 36" meter is a good starting point for testing crankcase pressure. \\ 
- 
-With the engine at operating temp and at idle, the vacuum will be the highest. \\ 
-The reason you need it to be fairly long is because a very slight difference in vacuum can easily cause the fluid to skyrocket especially when using water. \\ 
-You may need the larger adjustment range. \\ 
-When the bike is in perfect tune, you may get away with a shorter manometer. \\ 
-But if your bike is well tuned, you really don't need the manometer. \\ 
- 
-===== Selecting a liquid media ===== 
- 
-The best liquid to use depends on how much pressure you'll be measuring is the short answer. \\ 
-Typically, mercury or water is suggested. \\ 
-Mercury has a density of 13,600 kg/m3 whereas water only has a density of 1,000 kg/m3. \\ 
-Mercury manometers are typically used in high heat applications such as exhaust manifolds. 
- 
-Liquid manometers measure differential pressure by balancing the weight of a liquid between two pressures. \\ 
-Light liquids such as water can measure small pressure differences. \\ 
-Mercury or other heavy liquids are used for large pressure differences. \\ 
-For an indicating fluid 3 times heavier than water, the pressure measurement range is 3 times greater, but the resolution is reduced. \\ 
-Typically, there isn't a large amount of crankcase pressure generated in a Sportster engine. \\ 
-So slight changes that may be important in diagnosing ongoing wear would not be detected with heavier liquids. \\ 
- 
-Indicating fluids can be colored water, oil, benzenes, bromides, and pure mercury. \\ 
-When selecting an indicating fluid, check the specifications for specific gravity, operating temperature range, vapor pressure, and flash point. \\ 
-Corrosive properties, solubility, and toxicity are also considerations. \\ 
- 
-Liquid characteristics in a U-tube Manometer: ((https://www.fierceelectronics.com/components/manometer-basics)) \\ 
-  - Viscosity should be low. 
-  - Low surface tension is required. 
-  - The liquid should stick on the walls. 
-  - Should not get vaporized. 
  
 ===== How does it work? ===== ===== How does it work? =====

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