Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision Last revision Both sides next revision | ||
|
techtalk:ref:engmech07e [2020/10/02 22:05] hippysmack [Further Study of Internal Engine Pressure] |
techtalk:ref:engmech07e [2020/10/02 22:24] hippysmack [Further Study of Internal Engine Pressure] |
||
|---|---|---|---|
| Line 30: | Line 30: | ||
| * Better oil scavenging and keeping down pumping loss at high RPM. \\ 76< engines breath and scavenge from the same hole. \\ They may be more sensitive to wetsumping than later models because of this. The air can't jump ahead of the oil to the rotary breather. \\ Oil is thicker and doesn't compress. What does that do to air pressure behind it? \\ 77> engines breath and scavenge from different holes. \\ Makes for a more free flowing internal system. | * Better oil scavenging and keeping down pumping loss at high RPM. \\ 76< engines breath and scavenge from the same hole. \\ They may be more sensitive to wetsumping than later models because of this. The air can't jump ahead of the oil to the rotary breather. \\ Oil is thicker and doesn't compress. What does that do to air pressure behind it? \\ 77> engines breath and scavenge from different holes. \\ Makes for a more free flowing internal system. | ||
| - | We know downstroke pushes oil toward the oil pump. \\ | + | We know downstroke pushes oil toward the oil pump. Excess vacuum slows that process, can back up oil and cause wetsumping. \\ |
| - | Excess vacuum slows that process, can back up oil and cause wetsumping. \\ | + | |
| But, if the underside of the pistons are slight negative, it helps the rings seat without as much vibration and turbulence. \\ | But, if the underside of the pistons are slight negative, it helps the rings seat without as much vibration and turbulence. \\ | ||
| As a rule, rings sit on their own springiness when pistons go up and are forced against the wall by the combustion pressure that is allowed to pass behind them. ((thefrenchowl of the XLFORUM http://xlforum.net/forums/showthread.php?t=2077771&page=6)) \\ | As a rule, rings sit on their own springiness when pistons go up and are forced against the wall by the combustion pressure that is allowed to pass behind them. ((thefrenchowl of the XLFORUM http://xlforum.net/forums/showthread.php?t=2077771&page=6)) \\ | ||
| Line 59: | Line 58: | ||
| In contrast, the 77-up breather closes when the last piston is at bottom dead center (BDC). \\ | In contrast, the 77-up breather closes when the last piston is at bottom dead center (BDC). \\ | ||
| - | Is that extra vacuum taxed to the piston? | + | Is that extra vacuum taxed to the piston? \\ |
| The better the gaskets and seals, the more vacuum you can run. \\ | The better the gaskets and seals, the more vacuum you can run. \\ | ||
