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techtalk:ref:engmech07f [2020/10/02 16:14] hippysmack created |
techtalk:ref:engmech07f [2023/12/26 21:26] (current) hippysmack |
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| ====== REF: Engine Mechanicals - Sub-07F ====== | ====== REF: Engine Mechanicals - Sub-07F ====== | ||
| - | ====== Breather System Air Volume Test by DK Custom ====== | + | \\ |
| + | ====== Liquid Drag vs Fluid Drag ====== | ||
| - | The full article is on the DK Custom web site. [[http://www.dkcustomproducts.com/breather-system-flow-testing-results-video.htm]] \\ | + | ====== Liquid Drag ====== |
| - | This testing was done to find out: \\ | + | This is an this example of 'liquid drag' (as opposed to fluid drag, our real life medium). ((Dr Dick 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/page2?t=1204854&page=2)) \\ |
| - | How much air was passed out the breather vents at idle, under a load, at cruising speeds and on throttle let-off. \\ | + | Consider a 5 gal pail of latex & paint mixer that gets powered from your electric hand drill. \\ |
| - | And also the differences between a variety of HD engines, along with engines that had been hopped up with cams and or higher compression pistons/heads. \\ | + | |
| - | In this test, air was captured and measured as to how much water volume was displaced in a fixed period of time. \\ | + | What's the difference between liquid and a fluid? \\ |
| - | Taking the liquid ounce displacement, you can convert that to Cubic Feet Per Minute (CFM) | + | In this example, it's that a liquid is non-compressible (oil). \\ |
| - | There are 957.50649350649 U.S. fluid oz. in 1 Cubic Foot. \\ | + | A fluid is compressible(air or air-oil). \\ |
| - | Results: \\ | + | Stick the mixer in the middle of the pail about 1/2 way to the bottom in the center of the paint mass. \\ |
| - | Sportsters move the least amount of air through the breathers. \\ | + | Hit the trigger and the drill wants to twist out of your hand (liquid drag on the mixer). \\ |
| - | Twin Cams move the most amount of air through the breathers, with little difference between air cooled and Twin Cooled. \\ | + | As the mixer accelerates the paint, the drag reaction at the drill gets less. \\ |
| - | Milwaukee-Eights move more air than Sportsters, but little more than half as much as the Twin Cams through the breathers. \\ | + | And you can see the paint moving fast around the mixer and slow at the pail wall. \\ |
| - | Even more surprising is the least amount of air is moved on all bikes while at cruising RPM. \\ | + | |
| - | The only way to get a significant amount of air to move through the Sportsters was to get the RPM up around redline. \\ | + | Eventually you steer the mixer near the wall to get that stuff mixed and an important change happens. \\ |
| - | (and that crankcase pressure was probably because the valves were beginning to float) | + | The reaction at the drill gets less, the drill speeds up and the paint near the mixer speeds up with it. \\ |
| - | The most amount of air is moved through the breathers at idle, during hard acceleration and during deceleration. \\ | + | But the rest of the paint away from the mixer stops moving (as if its hanging in it's own 'miniature sump' away from all the commotion. \\ |
| - | A visual of this can be seen in this video: [[https://www.youtube.com/watch?v=Kio4DEuOpCU|DK Custom Breather System Air Volume Testing of Harley-Davidsons ]] \\ | + | |
| - | The actual numbers are in the chart below. \\ | + | That explains the less reaction force on the drill. \\ |
| - | (engines warmed up / oil level on midway mark of dipstick before testing) \\ | + | You're moving less than the full 5 gal now (and moving that small amount better with less drag) even though the amount in the pail is unchanged. \\ |
| + | This is important to understand. \\ | ||
| - | | **DK Customs Products Breather Report** (from different throttle / riding conditions) ||||| | + | Summary so far: \\ |
| - | |**Bike tested**|**CFM \\ (idle)**|**CFM \\ (cruise)**|**CFM \\ (hard acceleration)**|**CFM \\ (deceleration)**| | + | You're mixing the dickens out of 1/2 gal and cutting 4-1/2 gal out of the picture. \\ |
| - | |**Air Cooled Twin Cam (103)**|.2172|.08|.1952|.2504| | + | And that 1/2 is really moving and it's taken less force to move it because your moving less. \\ |
| - | |**Twin Cooled Twin Cam (103)**|.2548|.0972|.2231|.2874| | + | (less volume don't jive with the density-not volume- as in above) \\ |
| - | |**M8 Air Cooled (107)**|.1211|.06|.1059|.1127| | + | It's exactly the same if now you change to a 55 gal drum. \\ |
| - | |**Sportster (1250 with high compression)**|.0125|.0125|.0125|.0125| | + | 1/2 gal going fast but 54-1/2 not moving. \\ |
| - | |:::|At redline (6200 RPM) with no load (.3326 CFM)|||| | + | |
| - | |**Sportster (1200)**|.0626|.0626|.0626|.0626| | + | So the addition of a sump (containment area) allows a greater quantity of oil (paint) to be present in the case (pail) without any extra drag. \\ |
| + | |||
| + | Some of that oil is able to drop out of suspension so it can separate into the sump. \\ | ||
| + | Once the used oil gets sump trapped things are going good. \\ | ||
| + | But there are drag losses geting it to the sump as it flies outward off the rods. \\ | ||
| + | Some will land on the inside of the case near & on the parting seam. \\ | ||
| + | Some will travel down the inner walls of the wheels then fly off to the case wall. \\ | ||
| + | Some will fly up under the pistons where it needs to eventually find its way to the case wall also. \\ | ||
| + | |||
| + | In this chaotic environment, gravity isn't going to do much to drain it down to sump when there are giant flywheels whizzing 1/8" from this case walls. \\ | ||
| + | The wheels are going to set up a following flow on the walls. \\ | ||
| + | The better the following flow, the less oil in commotion. That's good. | ||
| + | |||
| + | But good movement is because of good dragging. \\ | ||
| + | But drag is bad. \\ | ||
| + | Good dragging sucks power. \\ | ||
| + | So does not dragging because the oil is slow moving. \\ | ||
| + | Oil is now making the fluid more dense. \\ | ||
| + | |||
| + | And what if you got no sump like 99.99% of 76< motors? \\ | ||
| + | This kind of drag is the main liquid drag. \\ | ||
| + | Its a 'no win' situation. \\ | ||
| + | A robbing Peter to pay Paul situation. \\ | ||
| + | |||
| + | ====== Fluid Drag ====== | ||
| + | Above, we've touched on the idea that oil in the flywheel cavity of the cases probably creates a drag on the rotating lower end, robbing power. \\ | ||
| + | And the amount of oil probably affects the amount of drag. \\ | ||
| + | More oil = more drag and causes it to increase the density of the fluid. \\ | ||
| + | //Fluid//, not liquid. \\ | ||
| + | |||
| + | This drag is like the drag that makes running in a swimming pool so difficult. \\ | ||
| + | This drag is sometimes the only drag that gets considered. \\ | ||
| + | The idea that 'the dryer the better' don't paint the whole picture. \\ | ||
| + | That drag is smaller than the power used up to physically 'pump' the oil-air fluid as the motor spins. \\ | ||
| + | The more dense the fluid, the more power is lost to pumping it. \\ | ||
| + | |||
| + | No matter the density of this fluid, its the action of the pistons that moves it from the flywheel cavity. \\ | ||
| + | On 76< motors, logically the way to accomplish this is to open the breather valve as the pistons fall so the max amount of 'fluid exhaust' occurs. \\ | ||
| + | Then close the valve as pistons rise. \\ | ||
| + | 77> motors have a reed valve or umbrella flapper that accomplishes the automatic opening and closing of the 'fluid exhaust port'. \\ | ||
| + | And it is not adjustable. \\ | ||
| + | |||
| + | In this example when the valve closes, then the piston rise creates a giant vacuum in the case. \\ | ||
| + | (with the vacuum being greatest at the highest point of piston travel) \\ | ||
| + | Just after this highest point the pistons start to fall again. \\ | ||
| + | This is when the valve opens again. (max exhaust right?) \\ | ||
| + | This vacuum sucks the previous expelled fluid back into the case resulting in the crankcase not actually getting dry. \\ | ||
| + | |||
| + | 77> engines deleted the timed open and closed breather valve as is in 76< motors. \\ | ||
| + | The camchest is always open to the flywheel cavity with a one way valve between the motor and the outside environment. \\ | ||
| + | The slang term "FooFoo" comes from the annoying sound that it makes when it gets clogged up with oil residue. ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/128453-crankcase-breathing-cycle/page3?t=1332902&page=3)) | ||
| - | **CFM**: Cubic Feet per Minute. \\ | ||
| - | **Deceleration Test**: Measured by chopping the throttle to 0% with the clutch in. \\ | ||
| - | **Cruise** (low load test): Typical RPM most riding takes place in (2500-3000 RPM). \\ | ||
