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| Hello, I'm new to the forum, but a multiple Plymouth owner. I have a 47 and a 58, and my question is... can anyone tell me about the crankcase ventilation on the 318 motor? I get smoke periodically coming out of the back of the engine tube that goes to the underside of the car. It's only noticeable when sitting a while at a stop light. Bad news? The engine is the original since the car was new in 58, with only 28K miles. Is this normal? My 47 flathead has very positive crankcase pressure and often spits oil out of the breather tube/filter, but never smoke. I realize it's a completely different engine, so I'm looking for ideas from fellow 318 owners. Thanks! |
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Location: N.W. Fla. | That the draft tube. Supposedly the draft going by will suck the nasty air out of the crankcase. Sitting @ a light the crankcase pressure builds up pushing it out & you notice it because you're not moving. Hard to say how much is too much, guess oil consumption would be the way to tell. |
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Location: Jamaica Plain, MA | It's basically gasses that blow-by the compression rings into the crank case. You don't see it with PCV devices because it gets sucked into the air-fuel mixture on the next cycle. It's a straight forward affair to do a compression test. Although, you might not want to. If it runs ok and doesn't use tons of oil or oil-fowl the plugs, knowing that each cylinder is off isn't going to lower your blood pressure. My cars with 301s and 318s usually did this to some extent. |
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | Yeah, but that crankcase vent, that dumps crap out, down by the trannie, sure messes up a clean undercarriage.
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Location: N.W. Fla. | You could replace the tube with an improvised PCV system. Groomet with PCV valve in the opening & find a vac source around the carb. |
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Location: Jamaica Plain, MA | I had a 62 Chrysler with CA emissions... Which was a crude tube that just routed the stuff to the outer part of the air cleaner. It got gunk in there. |
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Location: Las Vegas, Nevada | I decided to install a PCV system on my rebuilt 318. I replaced the road draft tube and open vented breather with a PCV valve and a later closed breather from a newer engine (mid 1960s California car.) I had a friend weld a steel elbow to a stock air cleaner to run a hose from the closed breather. I used the steel PCV mount which presses into the valve cover tube for the road draft tube. I could not use the mid 1960s carburetor due to the reversed throttle linkage, so I bought an aluminum spacer for my original carburetor and had a friend who is a good machinist modify it serve as a vacuum source for the PCV valve. Here is the spacer.
K.
Edited by Kenny J. 2012-07-08 5:59 PM
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Location: Las Vegas, Nevada | By the way, the Positive Crankcase Ventilation system was not invented as an emissions control device during the early 1960s. It dates back at least to World War Two. The original reason for its use was to keep dust and sand out of the crankcase of engines operated in dusty or desert environments. It was part of Chevrolet's "Export Package" in the 1950s for use in dirt and gravel road environments.
I've seen people post here that PCV systems put crankcase fumes into the combustion chambers and therefore must cause dirty deposits on the pistons and valves. Not likely when burned in the combustion process of a well tuned engine. Open draft systems, however, can allow condensation to build up in the crankcase and lead to sludge formation, even with detergent oil. Not as severe in frequently driven vehicles used for highway travel. But in vehicles driven short distances and/or infrequently it does happen.
The fact that PCV systems burn crankcase emissions which otherwise would be emitted into the environment as a byproduct is a coincidence which benefited automakers scrambling to meet the standards forced upon them. PCV valves have nothing to do with the lowered compression, retarded timing, lousy camshaft profiles, screwy carburetor settings/modifications and other stop-gap measures which were used to adapt engines not designed with consideration for emissions controls to meet said regulations. The poor performance, awful fuel economy and terrible warm-up characteristics of the mid to late 1970s had nothing to do with PCV systems.
Edited by Kenny J. 2012-07-08 8:28 PM
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | That would be a nice little cottage industry, for someone, to make up a simple, attractive, complete, closed PCV system for our cars.
The road draft tube's emissions are nasty.
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| That crankcase blowby was a large cause of the terrible smog we used to have. It's normal, that's why there's a large draft tube. But if ring wear gets to be too much, you'll start consuming oil and the smoke will get thicker and denser. Putting a PCV system on it ain't a bad idea. Me, I like them stock, and in California my 56 is exempt. |
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| I would buy one for sure!! |
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| Kenny,
Thanks for the pics and description of your work. Did you have any clearance issues with the stock airfilter and hood after installing the aluminum spacer?
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Location: Las Vegas, Nevada | kirkprentiss - 2012-07-10 6:25 AM
Kenny,
Thanks for the pics and description of your work. Did you have any clearance issues with the stock airfilter and hood after installing the aluminum spacer?
It's not installed yet, Kirk. But the different is only a half of an inch. There is a trick for measuring. Take some modeling clay and place it at the center of the air cleaner at the same thickness as the spacer. Close the hood and see if the clay gets crushed. If not, you're good. If it does get crushed, then run an air cleaner with a lower profile, as it isn't likely to find a thinner spacer.
The reason I did not use the mid 1960s carburetor was because the throttle action was the reverse of the late 1950s linkage. Had I been able to use it, which would have meant taking the linkage from the base of the '58 carburetor and installing that into the base of the '66 carburetor, which would have been tricky and tedious, I would have had to run a newer style air cleaner anyway, as the air horn on the newer carburetor was different.
K. |
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Location: N.W. Fla. | rbmain - 2012-07-08 7:23 PM
Putting a PCV system on it ain't a bad idea. Me, I like them stock, and in California my 56 is exempt. Cal. mandated the PCV system well before the requirement was nationwide. From what I've heard the car companies, after seeing the results in maintnace/warranty results, that supposedly they started installing them on cars nationwide before they were @ the deadline for implementation. |
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| Kenny J. - 2012-07-10 9:36 AM
kirkprentiss - 2012-07-10 6:25 AM
Kenny,
Thanks for the pics and description of your work. Did you have any clearance issues with the stock airfilter and hood after installing the aluminum spacer?
It's not installed yet, Kirk. But the different is only a half of an inch. There is a trick for measuring. Take some modeling clay and place it at the center of the air cleaner at the same thickness as the spacer. Close the hood and see if the clay gets crushed. If not, you're good. If it does get crushed, then run an air cleaner with a lower profile, as it isn't likely to find a thinner spacer.
The reason I did not use the mid 1960s carburetor was because the throttle action was the reverse of the late 1950s linkage. Had I been able to use it, which would have meant taking the linkage from the base of the '58 carburetor and installing that into the base of the '66 carburetor, which would have been tricky and tedious, I would have had to run a newer style air cleaner anyway, as the air horn on the newer carburetor was different.
K.
Kenny,
The clay is a great idea!! I was talking to my mechanic about this and he also suggested that there be a baffle in the valve cover to keep oil splash from being sucked up into carb. Have you done that too?
Thanks, Kirk |
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Location: Jamaica Plain, MA | I think most valve covers from the big and small blocks of the era had baffles. Anyway, I had a 62 300 from Utah that had been brought to CA by its owner in the early-mid 60's when she moved. It had black plates, and a somewhat home made looking PCV system. I was told this was to conform to CA standards. Who knows? It doesn't seem like an onerous mod, it gets rid of embarrassing smoke, and reduces smog. Of course it's not really original. |
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| JT Vincent - 2012-07-10 5:21 PM
I think most valve covers from the big and small blocks of the era had baffles. Anyway, I had a 62 300 from Utah that had been brought to CA by its owner in the early-mid 60's when she moved. It had black plates, and a somewhat home made looking PCV system. I was told this was to conform to CA standards. Who knows? It doesn't seem like an onerous mod, it gets rid of embarrassing smoke, and reduces smog. Of course it's not really original.
JT - yeah, for me it's getting rid of the embarrassing smoke and doing it in such a way that is not highly costly, and if I can, serve a function at the same time!
Edited by kirkprentiss 2012-07-10 8:02 PM
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | Yeah, Richard, "we" are exempt from having to install a smog system on our cars, but our car's undercarriage's are NOT
exempt from looking like Kuwaiti oil rigs, after the Gulf war...
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Location: Jamaica Plain, MA | If you're not pulling vacuum from the intake for power brakes, couldn't you just plumb into that? You'd want to run a hose from an otherwise sealed valve cover cap, run it through a positive pressure valve (common, cheap) and into the manifold. Easy! |
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Location: Las Vegas, Nevada | Baffles are a good idea.
K. |
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | You start by blocking off the crankcase vent tube.....
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Location: Las Vegas, Nevada | I checked. My '58 valve covers have baffles inside, right below the tubes.
K.
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Location: Jamaica Plain, MA | Yeah Neil's right. Block that off and get an oil cap for the drivers side that is sealed except for the tube to the positive air valve-manifold. A breather cap would also emit smoke if a lot is getting by the rings. |
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Location: WHEELING,WV.>>>HOME OF WWVA | the pcv doesn't really need to be sucked up by a vacuum port . most any decent , new after market air cleaner has a tube fitting on the underside . to fit the same to an oem air
filter case wouldn't take rocket science ---------------------------------------later |
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Location: N.W. Fla. | It's best to feed the fumes into the intake near the carb to keep it from overloading a cyl ot 2 if it isn't in a central location. W/o vacuum, how does the valve work? |
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Location: The not-so-great, dirty-white North ( Michigan) | Mopar1 - 2012-07-12 6:48 AM
It's best to feed the fumes into the intake near the carb to keep it from overloading a cyl ot 2 if it isn't in a central location. W/o vacuum, how does the valve work?
On most engines, when the engine stops, one or more valves are open. So the PCV vapors have a place to go and "thermosyphon" into those cylinders and then either into the exhaust as it cools or into the intake manifold. |
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Location: Blythewood, SC | JT Vincent - 2012-07-11 1:54 PM
Yeah Neil's right. Block that off and get an oil cap for the drivers side that is sealed except for the tube to the positive air valve-manifold. A breather cap would also emit smoke if a lot is getting by the rings.
If there is not an open side, won't it build pressure? I have a buddy who had two sealed caps on his valve covers and a PVC valve to the intake. The motor kept blowing out valley pan gaskets until I replaced one cap with a breather. He hasn't had a problem since. |
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Location: N.W. Fla. | 57plymouth - 2012-07-12 8:52 AM
JT Vincent - 2012-07-11 1:54 PM
Yeah Neil's right. Block that off and get an oil cap for the drivers side that is sealed except for the tube to the positive air valve-manifold. A breather cap would also emit smoke if a lot is getting by the rings.
If there is not an open side, won't it build pressure? I have a buddy who had two sealed caps on his valve covers and a PVC valve to the intake. The motor kept blowing out valley pan gaskets until I replaced one cap with a breather. He hasn't had a problem since. |
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Location: N.W. Fla. | DeSotohead - 2012-07-12 8:20 AM
Mopar1 - 2012-07-12 6:48 AM
It's best to feed the fumes into the intake near the carb to keep it from overloading a cyl ot 2 if it isn't in a central location. W/o vacuum, how does the valve work?
On most engines, when the engine stops, one or more valves are open. So the PCV vapors have a place to go and "thermosyphon" into those cylinders and then either into the exhaust as it cools or into the intake manifold. |
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Location: Las Vegas, Nevada | Mopar1 - 2012-07-12 8:44 AM
DeSotohead - 2012-07-12 8:20 AM
Mopar1 - 2012-07-12 6:48 AM
It's best to feed the fumes into the intake near the carb to keep it from overloading a cyl ot 2 if it isn't in a central location. W/o vacuum, how does the valve work?
On most engines, when the engine stops, one or more valves are open. So the PCV vapors have a place to go and "thermosyphon" into those cylinders and then either into the exhaust as it cools or into the intake manifold. System only works when the engine is running. With the engine running you want the nasty stuff distributed evenly around the 8 cyls, instead of gunking up one cyl if the stuff was plumbed into a single runner
'zactly!  Hence my decision to have a friend create the PCV port from a spacer. Hank knows my friend and knows he does good work.
K. |
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Location: On this barrel | I like the spacer and how you aren't afraid to admit your are running a two barrel. 
My 61 Dodge has the 318 with a two barrel, it was leaking gas pretty bad so I decided to put the Carter from my 56 on it, which is the "push" instead of the "pull" throttle action. Luckily the accelerator linkage (on the firewall) had a hole below the pivot point so I could convert it to "push". Slightly hooky since now the linkage rests on the engine, but ohh well |
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Location: The not-so-great, dirty-white North ( Michigan) | George...
I never stated that the PCV with the engine off worked well, but it will continue to provide the crankcase vapors, which are hotter, into the engine after it is shut off. You asked how it "worked" without vacuum, and thermosyphon effect, whereby the hotter gas rises and flows towards the cooler parts, is the methodology.
At least the vapors for the most part get trapped internally within the engine rather than escaping into the atmosphere. |
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca |
At least the vapors for the most part get trapped internally within the engine rather than escaping into the atmosphere.....AND:
condense/fall-out/get-trapped/what-ever...back onto the top of the engine compartment!
Edited by d500neil 2012-07-12 4:33 PM
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Location: Dorset, England | Kenny J - I'll buy one of your spacers. My 2bbl 325 is a heavy breather. I'm currently on mod#3 with breather hoses extended to the rear of the car. I made a nozzle on the breather cap and ran a hose to the air cleaner, but it didn't work so I just routed it to the back. Hoever it is easier for the fumes to vent out of the bottom of the cap than go down the hose and it still spoils a journey with the smell.
Please make a complete kit with a sealed filler cap, valve and the spacer plate. I suppose the ideal place to suck from is the valley cover. |
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| flattie45 - 2012-07-14 12:25 PM
Kenny J - I'll buy one of your spacers. My 2bbl 325 is a heavy breather. I'm currently on mod#3 with breather hoses extended to the rear of the car. I made a nozzle on the breather cap and ran a hose to the air cleaner, but it didn't work so I just routed it to the back. Hoever it is easier for the fumes to vent out of the bottom of the cap than go down the hose and it still spoils a journey with the smell.
Please make a complete kit with a sealed filler cap, valve and the spacer plate. I suppose the ideal place to suck from is the valley cover.
Kenny J - I'll buy one too!! |
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Location: N.W. Fla. | You have to have an inlet. The vented oil fill cap is a good choice where it's @ the other end of the engine. |
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Location: N.W. Fla. | DeSotohead - 2012-07-12 3:25 PM
George...
I never stated that the PCV with the engine off worked well, but it will continue to provide the crankcase vapors, which are hotter, into the engine after it is shut off. You asked how it "worked" without vacuum, and thermosyphon effect, whereby the hotter gas rises and flows towards the cooler parts, is the methodology.
At least the vapors for the most part get trapped internally within the engine rather than escaping into the atmosphere. from what I've heard...the air flowing past the end of the puke tube is supposed to create a low pressure situation that draws out the fumes. Obviously wouldn't work while idiling. |
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Location: The not-so-great, dirty-white North ( Michigan) | Mopar1 - 2012-07-14 2:30 PM
from what I've heard...the air flowing past the end of the puke tube is supposed to create a low pressure situation that draws out the fumes. Obviously wouldn't work while idiling.
George.....
You are referring to the road draft tube, which is NOT a PCV system.
And you are correct in that it only works with sufficient vehicle speed to provide the suction to evacuate the crankcase.
A PCV system (Positive Crankcase Ventilation) is by design made to create a continual flow of vapors from the crankcase (by way of the valve or valley cover) into the induction system to be burned along with the fuel/air charge from the carburetor.
But as the valve is located high on the engine, and the pintle in the valve provides an opening with no vacuum applied, the system will also thermosyphon the fumes back from the crankcase into the manifold or air cleaner, which at least keeps a lot of the vapors from getting straight into the atmosphere.
A PCV system must contain the following elements:
o A source for air to flow into the crankcase (either Air Cleaner if a "closed" PCV system or the oil filler tube/cap if an "open" system)
o An orifice of some sort to restrict flow with respect to engine vacuum
o A vacuum source attached to the restriction/valve that connects to the intake plenum
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | Ok, thanks Hank; now, somebody: go design a simple, elegant, hard-to-notice system that looks 'vintage', when you do
observe it.
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Location: Netherlands | DeSotohead - 2012-07-12 10:25 PM
At least the vapors for the most part get trapped internally within the engine rather than escaping into the atmosphere.
And you all really think that's a GOOD thing??? 
Americans worried about the atmosphere? Since when? Is that why you're driving big V8's?
Sorry guys, I've been biting my tongue ever since this thread appeared and it's now really getting on my tits...
Why anybody in their right mind would think that it's a good idea to dump any waste into their mixture/engine is way beyond me...
What you want is clean fuel/clean air to fill the cylinders. The air we use only to keep the particles of atomized fuel suspended in it by means of turbulence,
what we need from that air is volume only for compression and the oxygen for combustion. The more oxygen, the bigger the bang...
Now, do you really think it's a great idea to replace a big part of that fresh/cool/clean air/oxygen with warm/expanded/polluted garbage gasses/smoke?
Why do you have an airfilter? To go and dump hot, UN-filtered rubbish gasses into the nice clean mixture on it's way into the cylinders?
As these gasses are hot they'll take up twice the space that cold air does, with hardly any oxygen in it! And yes, the mixture is normally cold when it leaves the carb due to the speeding up of the air through the venturis, no matter how hot it is where you live, unless of course you're running a carb that's just too big and therefor lacks the air speed...
You'll spend time and money to get these engines to perform as best as they can, set up your carbs to be all perfect and then mess it all up by polluting that perfect mixture with a load of garbage and so rob your engine of valuable horses/fuel economy? Never mind the fact that the rubbish can pollute anything it meets on it's way in?
Yeah, right....
And all this just to hide/mask the fact that the engine obviously isn't in the best condition anymore? (What a surprise!) To meet some bullcrap emission laws?
Or just to do what the factory did for a quick solution without thinking for yourselves?
A healthy engine does not blow smoke from the draft tube....
Want more draft suction on stand still just as if you're driving and just so you can't smell it?
Connect the draft tube on a negative angle to the exhaust system, the rushing exhaust gasses will suck out all the fumes and they'll come out the rear,
where all the other waste products go...
Neil noticed how these gasses/smoke will mess up a clean undercarriage, do you really want that dirt in your mixture just to get rid of it?
If it was in the fuel or air filter you would ALL fall all over yourselves to make sure it got cleaned out!
Poor it down the manifold, sure, that's what to do...
Now, I'm not going to argue about this with anyone, (haven't got the time and can't be arsed either), you're all entitled to your own opinions, this is just my two cents worth....
Btw, this subject was already discussed before:
http://www.forwardlook.net/forums/forums/thread-view.asp?tid=38990&...
Keep 'em rolling, keep 'em clean, at least on the inside... 
Erik.
Edited by Windsor Wendy 2012-07-14 9:16 PM
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | ..I'm worried about the appearance/condition of H's UNDERCARRIAGE...and, oh, yeah, the environment, too!
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Location: Netherlands | Very funny Neil! I'll believe that last bit when I have some spare time... |
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Location: N.W. Fla. | Windsor Wendy - 2012-07-14 7:07 PM
DeSotohead - 2012-07-12 10:25 PM
At least the vapors for the most part get trapped internally within the engine rather than escaping into the atmosphere.
And you all really think that's a GOOD thing???
Americans worried about the atmosphere? Since when? Is that why you're driving big V8's?
Sorry guys, I've been biting my tongue ever since this thread appeared and it's now really getting on my tits...
Why anybody in their right mind would think that it's a good idea to dump any waste into their mixture/engine is way beyond me...
What you want is clean fuel/clean air to fill the cylinders. The air we use only to keep the particles of atomized fuel suspended in it by means of turbulence,
what we need from that air is volume only for compression and the oxygen for combustion. The more oxygen, the bigger the bang...
Now, do you really think it's a great idea to replace a big part of that fresh/cool/clean air/oxygen with warm/expanded/polluted garbage gasses/smoke?
Why do you have an airfilter? To go and dump hot, UN-filtered rubbish gasses into the nice clean mixture on it's way into the cylinders?
As these gasses are hot they'll take up twice the space that cold air does, with hardly any oxygen in it! And yes, the mixture is normally cold when it leaves the carb due to the speeding up of the air through the venturis, no matter how hot it is where you live, unless of course you're running a carb that's just too big and therefor lacks the air speed...
You'll spend time and money to get these engines to perform as best as they can, set up your carbs to be all perfect and then mess it all up by polluting that perfect mixture with a load of garbage and so rob your engine of valuable horses/fuel economy? Never mind the fact that the rubbish can pollute anything it meets on it's way in?
Yeah, right....
And all this just to hide/mask the fact that the engine obviously isn't in the best condition anymore? (What a surprise! ) To meet some bullcrap emission laws?
Or just to do what the factory did for a quick solution without thinking for yourselves?
A healthy engine does not blow smoke from the draft tube....
Want more draft suction on stand still just as if you're driving and just so you can't smell it?
Connect the draft tube on a negative angle to the exhaust system, the rushing exhaust gasses will suck out all the fumes and they'll come out the rear,
where all the other waste products go...
Neil noticed how these gasses/smoke will mess up a clean undercarriage, do you really want that dirt in your mixture just to get rid of it?
If it was in the fuel or air filter you would ALL fall all over yourselves to make sure it got cleaned out!
Poor it down the manifold, sure, that's what to do...
Now, I'm not going to argue about this with anyone, (haven't got the time and can't be arsed either ), you're all entitled to your own opinions, this is just my two cents worth....
Btw, this subject was already discussed before:
http://www.forwardlook.net/forums/forums/thread-view.asp?tid=38990&...
Keep 'em rolling, keep 'em clean, at least on the inside...
Erik. |
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Location: Las Vegas, Nevada | Mopar1 - 2012-07-15 6:19 AM
Sounds like you are confusing a PCV system with an EGR system.
Agreed! The EGR is a very nasty affair, causing some of the issues I listed in a comment above. The PCV system, however, keeps underhood dirt out of the crankcase and also removes condensation, helping to avoid sludge build-up, which can occur even with frequent oil changes.
Granted, the meshing inside the valve cover intake breather can be very effective at keeping dust and dirt out of the crankcase if properly maintained, but the PCV system helps prevent mositure from gathering inside.
K. |
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Location: Netherlands | Well George, that's a well known saying in the English speaking world...But no worries, in my case the tits in question would be all muscle...
And euuhh, WTF is an EGR system??? With a name like that it sounds like it should instantly be removed....
Kenny, by no means did I mean to rain on your parade or anything, nor was my ranting meant for you in particular...
Your parts are nicely made and I'd love to use one of those should I need a vacuum source, for anything other than a pcv system, a matter on which I think my views are clear.
So that makes two or even more of us not afraid to admit to be using a 2bbl carb...
In my opinion moisture does not occur in well ventilated spaces and I totally agree that sucking the gasses out is favorable if replaced with fresh filtered air,
without creating unwanted crankcase vacuum, I just fail to see why anyone would dump the rubbish in the mixture...
So to those who want to order these from Kenny for whatever purposes y'all see fit, by all means do so!
Nice part and a million times nicer than drilling into the manifold...
Edited by Windsor Wendy 2012-07-15 6:44 PM
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Location: N.W. Fla. | Windsor Wendy - 2012-07-15 3:30 PM
Well George, that's a well known saying in the English speaking world...But no worries, in my case the tits in question would be all muscle...
And euuhh, WTF is an EGR system??? With a name like that it sounds like it should instantly be removed....
EGR is Exhaust Gas Redistribution Started in the 70s. They siphon ex gas out of the exhaust & route it into the intake manifold. Reduces emissions & supposedly cools the chamber(with hot ex gas???) As far as humidity...here in Florida we got it! Even on engines with PCV occasionally oil on the dipstick 1st thing in the morning will have a creamy white milkshake look to it. |
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Posts: 3186
Location: The not-so-great, dirty-white North ( Michigan) | Exhaust Gas Recirculation, or EGR, reduces the peak combustion temperatures and pressures by using the "dead" exhaust gas as a dilutent in the chamber.
The way it works is the spark is ignited by the plug, but since the mixture of good fuel/air gas is diluted by a percentage of recirculated exhaust gas, the flame front of the burn kernal in the chamber progresses across the chamber slower than if it was a full clean fuel/air charge.
Since the burn is slower, it takes longer to reach the end-point burn.
By that time the piston has travelled farther down the bore so the normal peak pressure and temperature is lower than without it.
This also means that to get some of the performance back, vehicles with high EGR rates need a little more sprk advance than without it.
The end effect is that since the temperatures and pressures are lower, the amount of chemical combining of N2 and O2 is lower, so NOx emiisions are lower.
It does nothing really for reducing the HC and CO emissions, and if the rates are too high, even can be detrimental as misfire or partial burns occur which increase those components of the exhaust.
This strategy was first used when vehicles were open loop carbureted and had only oxidation (HC and CO) catalysts, and needed to reduce the NOx.
As reduction (NOx) and 3-way (HC, CO and NOx) catalysts became common with closed-loop controls systems (the infamous O2 sensor), the need for high rates of EGR was removed from engines.
In fact, some engines were able to meet emissions requirements with no EGR and only some changes to overlap of the intake and exhaust valve events (internal EGR).
Now vehicles mostly use variable valve timing as a way of getting overlap periods needed for internal EGR, and no other external EGR valve system is needed.
Erik...every vehicle engine has some EGR due to the cam overlap. In fact, those real "lumpy cams" liked by hotrodders actually have more than the mild grocery getter variety engine.
It is simply a matter of the physics of the engine. |
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Extreme Veteran
Posts: 395
Location: Netherlands | Something getting on ones tits meaning something getting on ones nerves..."It's the tits" as in "it's great"?
Overhere when something's the best, then it's "the dog's bollocks"! And a fanny is a p***y overhere, or a snatch if that'll overcome the friendly censorship...
Just as I thought, this EGR crap would instantly be removed if it came anywhere near me...
As I see it, the PCV system does more or less the same thing, diluting the mixture with waste gasses...
Sure Hank, I see what you mean on the valve overlap front...
Now here's where we get to the complicated cam timing/profile/lift/duration and exhaust design/back-pressure interaction.
The overlap is needed for the fresh mixture to force out any remaining exhaust gasses as the mixture is filling the cylinder.
In doing this a part of the fresh mixture will also escape into the exhaust.
Now, in an ideal situation the right amount of exhaust back-pressure would push that escaped mixture back into the cylinder just before the valve closes. No more, no less...
It's a very delicate/precise interaction and it's very easily upset by changing the combination, losing fresh mixture from the combustion cycle or indeed causing the EGR effect...
As ideal/perfect interaction is usually pretty far removed from what we actually have/can achieve, it's our job to get these values as good as we can for best performance.
Remains the question: WTH would we want to make things worse by dumping waste gasses into the mix???
In case of the lumpy hotrodders cams, fuel economy/engine longevity does not come into the equasion I don't think and it's all about WHERE do you want the horses to kick...
From the word go or starting around 3K?
Sure with a massive cam lift/duration you'd cram more mixture into the cylinders and are therefor able to take some losses in the process and still end up with more than you had before.
But wasn't this discussion about optimizing what we have and getting the best possible results from our cars as they are?
Y'all be very hard pushed to make me change my mind on this matter, in my book PCV and definitely EGR belong in the bin as both are robbing us of what we want from what we have, horses and best possible fuel economy at the same time...
Yes, pig-headed, I know...
Edited by Windsor Wendy 2012-07-16 6:55 AM
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Board Moderator
Posts: 3186
Location: The not-so-great, dirty-white North ( Michigan) | Windsor Wendy - 2012-07-16 6:48 AM
Sure Hank, I see what you mean on the valve overlap front...
Now here's where we get to the complicated cam timing/profile/lift/duration and exhaust design/back-pressure interaction.
The overlap is needed for the fresh mixture to force out any remaining exhaust gasses as the mixture is filling the cylinder.
In doing this a part of the fresh mixture will also escape into the exhaust.
Now, in an ideal situation the right amount of exhaust back-pressure would push that escaped mixture back into the cylinder just before the valve closes. No more, no less...
It's a very delicate/precise interaction and it's very easily upset by changing the combination, losing fresh mixture from the combustion cycle or indeed causing the EGR effect...
Erik...
You are somewhat correct in your above assessment, but additionally the intake gets some backflow when the intake valve opens since due to exhaust backpressure and the fact that the chamber is positively pressurized with the combustion gases versus the vacuum in the intake manifold there is reversion at "blowdown" when the intake valve opens. First exhaust is pushed into the inlet, then this reverses as the pistons get towards BDC, the fresh charge comes in and savanges the chamber blowing residual exhaust gas, along with some fresh charge, out the exhaust until the exhaust valve fully closes.
The lumpiness of the hot cams is due to the fact that with the greater overlap due to early intake opening and later exhaust closing this is made worse, as the cycle-to-cycle efficiency of each cylinder varies and so does the combustion.
Of course, as the engine rpms climb, the inertial ram effect of the gas velocity in the intake manifold and ports overcomes a lot of this, and when the effect is neutralized, the engine then picks up power across a small increase in further rpm.
This is where the term "coming on the cam" originates.
In highly tuned engines, all factors of intake runner length and diameter, plenum volume, cam lift/duration/seperation angles, valve size, compression ratio, combustion chamber layout, exhaust port and manifolding and length and tuning of the exhaust system in terms of pipe diameters and lengths and the backpressure of the mufflers/resonators (if any) are all designed to work together.
In these cases, you can have normally aspirated 2-valve per cylinder engines that have greater than 100% volumetric efficiencies for large portions of their operating range. This can lead to HP/cu in numbers greater than 1, and in some cases close to 2 HP/cu in. I refer you to the Hot Rod "Engine Masters" series of magazines for details of what engines and how its done.
And, BTW, these engines typically do not have any PCV or EGR systems. But they are dyno engines (like thoroughbred horses), and get oil changes in the several hour range....... |
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Inactive by user's request
Location: Las Vegas, Nevada | Windsor Wendy - 2012-07-15 1:30 PM
So to those who want to order these from Kenny for whatever purposes y'all see fit, by all means do so!
Nice part and a million times nicer than drilling into the manifold...
Order what? I'm not making and selling these. I had a friend modify the spacer for me. I live in the desert, where it is windy and dusty. I want a closed crankcase ventilation system for my own usage. Just showing how I'm doing it. Moisture in the crankcase can be an issue with infrequently driven vehicles.
K. |
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Crankcase ventilation smoke
