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| Pros & Cons of getting rid of PCV system.....; By just venting blow by gas into the air. | |
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| Tweet Topic Started: Nov 8 2014, 11:39 PM (3,676 Views) | |
| Greywolf | Nov 11 2014, 08:57 PM Post #31 |
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Mostly Harmless
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If your mill is sucking up that much oil, you have a problem in it that the PCV won't fix. Either the valve cover vent is drawing oil out of the engine that it shouldn't be allowing to get near it, or the blowby pressures are indicating a serious ring and piston clearance issue. Under normal conditions, there is very little vapor coming up out of the engine, and a vacuum or a partial one exists in the block and valve cover. If there is a constant flow of gasses coming up out of the main section, you prolly got bad rings period. |
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| Rondawg | Nov 11 2014, 09:15 PM Post #32 |
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I had asked earlier if a motor uses 1/2 a quart between oil changes it has no leaks, then is all of that lost oil is sucked thru the pcv and thru the intake? Someone said even if it was a quart between changes is lost that no problemo. Ive got about 1500 miles on my 1st oil change and oil is barley down at all. I dunno what is normal for oil consumption I really don't care at this point. I was just trying to learn about how to eliminate any oil from going tbru the throttle body/intake/indirectly the exhaust manifold by shit canning the pcv. Edited by Rondawg, Nov 11 2014, 09:17 PM.
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| Greywolf | Nov 11 2014, 09:34 PM Post #33 |
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Mostly Harmless
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There IS another possibility - and I have seen this one too, but it can be hard to track down and eliminate. GIVEN: There should be at least a partial vacuum in the PCV system. One thing that can add pressure is rings allowing too much blow-by gassing yeah.... But because the PCV line is usually connected either to the air cleaner, or to a hard vacuum fitting on the intake, if there is /are a lot of leaking gaskets around the valve cover, engine block, and so on- there can be a full flow of air into the engine and out through the PCV line to the intake, and if that is high enough it will pull oil vapor and droplets along with it. The PCV Valve isn't a restriction to limit the flow - what it does is prevent engine backfire from lighting explosive gases in the engine. It's a one way valve for that purpose mainly. PCV should not be confused with EGR by the way. EGR is Exhaust Gas Recirculation, and was invented to re-burn some of the unburnt petro products in exhaust gas. Carbs and injection systems for an EGR machine are designed to provide more fuel to make up for lean burn, among other conditions - but all that is ancient history for the most part because burning the waste products is what Catalytic Convertors are supposed to do for us. EGR Valves only open under high vacuum conditions, I think... But anyway, an incompletely sealed crank case or a bad valve cover gasket can also cause oil to be sucked right out of the valve cover. Rear main seals can also do that, ditto the front crank seal, and timing case gasket set. NOTE on EDIT: One of the prime offenders for that condition is an oil filler cap that has a bad gasket, or none at all. Edited by Greywolf, Nov 11 2014, 09:39 PM.
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| perfesser | Nov 11 2014, 10:47 PM Post #34 |
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Elite Member - Former Metro owner
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In the immortal words of the late, great R. Reagan - "now there you go again!" Please find me even one place in anything I wrote where I suggested you should do dyno testing. I'll wait. ... <crickets> ... The only time I even used the word "dyno" was in relation to subjective "seat of the pants" impressions. There are plenty of ways to test objectively what you're looking for without using a chassis dyno. Sheeshh!! |
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| Greywolf | Nov 11 2014, 10:58 PM Post #35 |
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Mostly Harmless
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Umm... Fellas? I'm really doing my best to give you some stuff that will be useful tools you can use forever. If you can find it in yourselves to "Agree to Disagree" I've got a lot more cool stuff for ya... Besides, Rondawg is right - that's way too much oil consumption. (?) I wonder how Rosie O'Donnel would read on a "BUTT DYNO", but I digress
Edited by Greywolf, Nov 11 2014, 11:02 PM.
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| Rondawg | Nov 11 2014, 11:58 PM Post #36 |
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Here is a photo for a good "seat of the pants comparison" and no dyno needed. Oil in the catch can means less oil being burned. Less oil being burned is good.
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| Mrbreeze | Nov 12 2014, 12:18 AM Post #37 |
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Mine is still connected as originally designed, I have no oil tracking in the air box, 241,000 miles, never have had to crack open the motor, other than pan and valve cover gaskets and front, rear, cam seals, preventative maintenance goes a long way, I drive it like I stole it, I hammer on it, what I'am trying to say is I drive it HARD, and it takes it, I always look under the hood and check stuff out though, when it's 1/2qt low on oil, it's time to change it. If you are getting oil into the intake you have problems.. When the motor functions correctly you will not get oil into the intake, via PVC or air filter box, it's simple as that.. |
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| Rondawg | Nov 12 2014, 12:58 AM Post #38 |
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That's EXCELLENT! I hope someday I can say something similar. Mine is a fresh rebuild and now that it has a couple thousand miles on it, perhaps I should drive it harder! |
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| vr4 | Nov 12 2014, 01:54 AM Post #39 |
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Want to eliminate the carbon buildup you're talking about? Run e85 or propane instead of gasoline. |
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| Rondawg | Nov 12 2014, 02:11 AM Post #40 |
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Sounds possible.....however I'm no hydrocarbon expert. Apparently (or so i am told anyways) raw unburned vaporized gasoline leaves carbon deposits so unburned propane might do the same thing Maybe I need to check my old gas jugs for carbon buildup.
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| Old Man | Nov 12 2014, 03:42 AM Post #41 |
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might oughta do what ever your common sense tells you to |
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| Metromightymouse | Nov 12 2014, 06:12 AM Post #42 |
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Powdercoat Wizard
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Gee, when I opened up my 68 beetle motor there was carbon on the pistons and it had the vent to atmosphere set up. I scraped all the carbon off before I put it back together and a couple of years later when I broke it open again they were all carboned up again. Don't think it was from oil. Rondawg, I think you misinterpreted Perfesser's intent. He was essentially saying he did not have any better argument or any other information other than what he had provided. The fact that you have made the same argument over and over points to the fact that you seem to have made up your mind and he conceded to your determination and asked that you report tested data results (in concession to Myredvert, as well as a person can do in the real world, admittedly not true A/B/A testing) that you experience. Since we have been known to add MMO to gas in quantities that would seem to be greater than normal PCV levels with no ill effects, I would think that would be further evidence that some oil in the combustion chamber is not a problem. |
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| Woodie | Nov 12 2014, 06:52 AM Post #43 |
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That is not the case at all, EGR came AFTER catalytic converters, and the amount of exhaust gas run back through the engine in miniscule compared to the amount going out the pipe. The purpose of the EGR system is to dilute the intake charge, reducing combustion chamber temperatures, and thereby reducing the production of NOx (oxides of nitrogen). There is a side benefit of effectively reducing the size of the engine at cruise, forcing you to open the throttle further, which reduces the pumping losses and increases mileage slightly. |
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| Rondawg | Nov 12 2014, 10:10 AM Post #44 |
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That makes total sense to have some carbon on the pistons. You will never get a total complete 100% burn each time the spark plug lights off. I would guess that if your ole VW had a closed loop pcv system & had been burning extra oil as opposed to venting it, there would have been more carbon on the pistons? As for MMO I don't know what's in that stuff....its a mystery! I've used it, my dad swore by it. I don't think burning mmo with gas is a fair comparison to burning crankcase oil. MMO (whatever is in that stuff) is formulated to burn and clean. 5 W 30 motor oil is formulated to lubricate while withstanding high temps and not burning. Maybe I am wrong (it would not be the 1st or last time) but it seems these facts we can agree on: * Is it good to get blow by gas out of the crank case....YES *Does a PCV system accomplish this with less air pollution....Yes *There is no benefit to the intake system or top end to burn oil fumes & blow by gasses. Maybe no harm but certainly no benefits. Is there a better way to purge these oil fumes & gasses from the crankcase other than re-burning them thru the intake system....that's what I wanna know! Edited by Rondawg, Nov 12 2014, 10:21 AM.
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| perfesser | Nov 12 2014, 10:45 AM Post #45 |
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Elite Member - Former Metro owner
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Dozens of automobile manufacturers with thousands of skilled engineers spending billions of research dollars over the last 40+ years have not found one. YMMV. |
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Maybe I need to check my old gas jugs for carbon buildup.

7:57 PM Jul 10