Differences
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| - | techtalk:ref:engmech07 [2023/12/26 18:01] – hippysmack |
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| + | techtalk:ref:engmech07 [2023/12/26 19:55] (current) – hippysmack |
| @@ Line -42,5 +42,5 @@ | |
| ===== 1977-1985 ===== | |
| The one way breather style system is more like a car PCV system. ((mrmom9r of the XLFORUM | |
| A deep (dry) sump was added to 77> casings and the scavenge side of the oil pump pulls the oil from the scavenge port in the rear of the sump area. \\ | |
| Holes were added between the crankcase and the gearcase wall (much the way your car's crankcase is vented out the top thru the valve covers) \\ | |
| @@ Line -48,5 +48,5 @@ | |
| So the gearcase is also pressurized. Crankcase pressure is sent thru the one way valve in the cover and then vented to atmosphere out the vent. \\ | |
| However, crankcase ventilation works a little differently on these motors than a Chevy. ((aswracing of the XLFORUM | |
| What you see on cars is an inlet, generally coming from the air filter, into the motor. Then an outlet, regulated by a PCV valve, going into the intake manifold. \\ | |
| So it's designed to flow a little air through the system. \\ | |
| @@ Line -65,9 +65,9 @@ | |
| The oil is separated from the air by way of collision. Everything the air/oil mix touches on the way to the vent separates some oil from the air. \\ | |
| On piston downstroke, drain oil is pushed into the oil galley and crankcase air pressure is pushed into the gearcase and the breather valve is pushed open. \\ | |
| The air/ oil mist is slung around in the gearcase where it bounces on cam gears, case walls, etc. \\ | |
| Remaining air / oil mist flows toward the vent. \\ | |
| On | |
| On L84-85 engines, the slinger washer was removed and a breather baffle tube was installed in the cover to separate oil. \\ | |
| Oil hits the breather baffler tube then the back side of the breather valve to separate from the air and drains back into the gearcase. \\ | |
| @@ Line -82,4 +82,5 @@ | |
| {{: | |
| ====== Engine Breather Valves ====== | |
| ===== Sub Documents ===== | |
| @@ Line -96,8 +97,7 @@ | |
| ==== Symptoms of Breather Valve Problems ==== | |
| **The most notable signs of breather valve problems include weeping / leaking gaskets or blown gaskets / seals**. \\ | |
| Stopped up breather valves won't allow the engine to breath well and can create excess vacuum and implode gaskets. \\ | |
| Or it contributes to too high of oil density and slings excess oil out. Other factors are involved so results will vary. \\ | |
| @@ Line -124,6 +124,6 @@ | |
| * See also in the Sportsterpedia: | |
| * [[techtalk: | |
| ==== In the crankcase air system ==== | |
| Crankcase air pressure is mainly generated by the up and down movement of the pistons. \\ | |
| Additional air pressure is created by blowby from the combustion chambers past the rings and into the crankcase. \\ | |
| @@ Line -133,5 +133,4 @@ | |
| ==== The pressure in the crankcase is not from oil pump pressure ==== | |
| Static oil pump pressure has already been dissipated by the time it reaches the crankcase. \\ | |
| (although it takes static oil pressure to get the oil from the pump to the crankcase) \\ | |
| @@ Line -143,5 +142,4 @@ | |
| ==== Role of the breather valve ==== | |
| CC pressure both pushes to and sucks from the breather valve. \\ | |
| The breather valve allows for controlled air pressure to both leave and enter the engine to obtain what is referred to as a " | |
| @@ Line -156,5 +154,4 @@ | |
| ==== Affects of the 45° Rod / Piston Arrangement ==== | |
| 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. \\ | |
| This constant push / pull from offset pistons contributes to an imbalance of pressure that needs to controlled. \\ | |
| @@ Line -163,6 +160,5 @@ | |
| ==== Differential Pressure (vacuum and air pressure) ==== | |
| Vacuum and (positive) air pressure are the terms that describe the amount of molecules of a gas in a given unit of space. ((Dr Dick of the XLFORUM | |
| More molecules inside the engine than outside = inside air pressure. \\ | |
| Less molecules inside the engine than outside = inside is vacuum pressure. \\ | |
| @@ Line -181,19 +177,17 @@ | |
| A vacuum condition when downstroke begins lessens the restriction on the descending pistons and doesn' | |
| In most engines negative crankcase pressure allows less ring pressure and the combination of both means more hp. ((maru of the XLFORUM | |
| Over the years folks have used exhaust system energy to pull pressure from the case for this reason. \\ | |
| Guys have won championships with an engine that had an electric vacuum pump to reduce (positive) crankcase air pressure. \\ | |
| Crankcase pressure in these engines fluctuate wildly from positive to negative. ((maru of the XLFORUM | |
| However, high vacuum can have a dramatic affect on scavenging. \\ | |
| __See, Differential Pressure, in the sub documents at the top of this page for more information__. \\ | |
| ==== 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 | |
| Sweating oil from the cylinder base gaskets and rocker boxes. \\ | |
| As well as the push rod tubes and lifter blocs on the other side. \\ | |
| @@ Line -202,7 +196,7 @@ | |
| 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 | |
| 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 | |
| So you can bet some of this tremendous pressure is entering into your crankcase instead of 100% of it exiting your exhaust pipes. | |
| @@ Line -215,5 +209,4 @@ | |
| ==== What causes extra air in the crankcase? ==== | |
| Ring seal, as mentioned, is not as good on higher RPM even on a healthy engine. \\ | |
| Gasket / air leaks can introduce more air in the crankcase. \\ | |
