Differences
This shows you the differences between two versions of the page.
| techtalk:ref:engmech07d [2020/10/02 15:41] – created hippysmack | techtalk:ref:engmech07d [2023/12/26 21:24] (current) – hippysmack | ||
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| Blowby pertains to the condition of ring seal at the cylinders / pistons. \\ | Blowby pertains to the condition of ring seal at the cylinders / pistons. \\ | ||
| Combustion above the piston is pushed past the rings and into the crankcase. \\ | Combustion above the piston is pushed past the rings and into the crankcase. \\ | ||
| - | It is fundamentally just exhaust that went past the rings instead of out the exhaust port. ((aswracing oftheXLFORUM | + | It is fundamentally just exhaust that went past the rings instead of out the exhaust port. ((aswracing oftheXLFORUM |
| It's depleted of oxygen, it's hot, and it picks up moisture and oil in it's travels through the crankcase and into your intake tract. \\ | It's depleted of oxygen, it's hot, and it picks up moisture and oil in it's travels through the crankcase and into your intake tract. \\ | ||
| So it's displacing oxygen in the intake charge (through the air cleaner) that would otherwise contribute to combustion. \\ | So it's displacing oxygen in the intake charge (through the air cleaner) that would otherwise contribute to combustion. \\ | ||
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| It's well worth it to remove it from the intake tract and vent it to the atmosphere or exhaust instead. \\ | It's well worth it to remove it from the intake tract and vent it to the atmosphere or exhaust instead. \\ | ||
| - | What actually 'blows by' the rings and into the crankcase is a mix of unburnt fuel, water, soot, acids etc. ((bunny32 of the XLFORUM | + | What actually 'blows by' the rings and into the crankcase is a mix of unburnt fuel, water, soot, acids etc. ((bunny32 of the XLFORUM |
| - | Regarding blowby at high revs, the key factor is ‘ring-flutter’ or ‘ring-seal’. ((bunny32 of the XLFORUM | + | Regarding blowby at high revs, the key factor is ‘ring-flutter’ or ‘ring-seal’. ((bunny32 of the XLFORUM |
| 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. \\ | Then at warm idle, it starts. Above idle it either drops off or holds constant, as revs go up. \\ | ||
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| **Gapless rings**: \\ | **Gapless rings**: \\ | ||
| - | < | + | < |
| Basically, the better your ring seal, the more likely you are to have a wet sumping issue. \\ </ | Basically, the better your ring seal, the more likely you are to have a wet sumping issue. \\ </ | ||
| - | A lot of guys who work on a lot of gas/ | + | A lot of guys who work on a lot of gas/ |
| It traps pressure under the top ring. \\ | It traps pressure under the top ring. \\ | ||
| In fact the trend has become to run the gaps looser on the second ring to allow what gets thru the top to not get stuck. \\ | In fact the trend has become to run the gaps looser on the second ring to allow what gets thru the top to not get stuck. \\ | ||
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| ==== New ring / cylinder install ==== | ==== New ring / cylinder install ==== | ||
| - | Neither new rings nor cylinder bores are perfectly round. ((aswracing of the XLFORUM | + | Neither new rings nor cylinder bores are perfectly round. ((aswracing of the XLFORUM |
| As a result, when you put a new ring on a piston and into a new bore, there' | As a result, when you put a new ring on a piston and into a new bore, there' | ||
| The honing process puts a texture on the cylinder wall that allows the ring to machine the wall into the same shape as the ring during operation. \\ | The honing process puts a texture on the cylinder wall that allows the ring to machine the wall into the same shape as the ring during operation. \\ | ||
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| The ring is said to be " | The ring is said to be " | ||
| - | < | + | < |
| It has a huge amount to do with the accuracy of the boring job as well as the accuracy of the rings used. \\ | It has a huge amount to do with the accuracy of the boring job as well as the accuracy of the rings used. \\ | ||
| If it was bored perfectly and the ring was perfectly round, there would be no seating even needed.</ | If it was bored perfectly and the ring was perfectly round, there would be no seating even needed.</ | ||
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| ==== Ring seating during break-in ==== | ==== Ring seating during break-in ==== | ||
| - | There is a risk of ring microwelding by getting too aggressive in the break-in. ((aswracing of the XLFORUM | + | There is a risk of ring microwelding by getting too aggressive in the break-in. ((aswracing of the XLFORUM |
| HD's break-in procedure, and S& | HD's break-in procedure, and S& | ||
| Be gentle on the motor, don't put it in a situation that makes it hot. \\ | Be gentle on the motor, don't put it in a situation that makes it hot. \\ | ||
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| ==== Normal blowby ==== | ==== Normal blowby ==== | ||
| - | + | In the absence of any blow-by getting past the rings, the crankcase alternates from atmospheric (pistons down) to a vacuum (pistons up). ((aswracing of the XLFORUM | |
| - | In the absence of any blow-by getting past the rings, the crankcase alternates from atmospheric (pistons down) to a vacuum (pistons up). ((aswracing of the XLFORUM | + | |
| But in the real world, a little gets past the rings, so there' | But in the real world, a little gets past the rings, so there' | ||
| - | Conventional rings have a ring gap and the combustion pressure is very great. ((Deimus of the XLFORUM | + | Conventional rings have a ring gap and the combustion pressure is very great. ((Deimus of the XLFORUM |
| So you can bet some of this tremendous pressure is entering into your crankcase instead of 100% of it exiting your exhaust pipes. | So you can bet some of this tremendous pressure is entering into your crankcase instead of 100% of it exiting your exhaust pipes. | ||
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| ==== Testing ring seal ==== | ==== Testing ring seal ==== | ||
| - | A leak down test is the best way to check ring seal. ((aswracing of the XLFORUM | + | A leak down test is the best way to check ring seal. ((aswracing of the XLFORUM |
| 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. \\ | ||
