Honda Car Forum

"Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote
> "Caroline" <caroline10027remove@earthlink.net> spake
> > Tegger wrote:
> > snip non-rebuttal
> >> It is necessary that BOTH the crankcase breather AND the PCV valve
> >> get plugged.
> >
> > We've been over this. If the PCV valve plugs, that's one less path for
> > the crankcase gases to escape. Steady state crankcase pressure thus
> > will be higher with a plugged PCV valve. This places more pressure on
> > various oil seals. Thus they may fail sooner.
>
> Wrong. Totally incorrect understanding of the PCV system.

Nope; dead-on correct.

For the rational among us trying to learn about pressure: Think of the crankcase
as a bucket of water being fed with a hose but also having two holes in the
bottom of it. The rate of water flow and the hole sizes are such that 4 inches
of water are maintained in the bucket with this setup. If one suddenly plugs one
of the holes, what happens to the water level in the bucket?

It goes up. Just like the pressure in the crankcase will be higher, on average,
with a plugged PCV valve.

> And even if plugged, a PCV valve will NOT affect mileage.

Forgot to add that various Chilton's manuals also comment on how a
malfunctioning PCV valve may affect mileage. E.g. from the Ford Taurus/Mercury
Sable 1986-1992 Chilton Manual:

"Do not remove the PCV valve system from the engine, as doing so will adversely
affect fuel economy and engine ventilation with resultant shortening of engine
life." -- Emissions Controls, Page 4-6

Re your internet myth "theory":
Guess folks should ignore all the "internet wisdom" that says change your car's
oil every so often, too.

George Macdonald <fammacd=!SPAM^nothanks@tellurian.com> spake unto the
masses in news:bc8fc0dfrepdi5jr189vm8mcckpfanrlbd@4ax.com:


> Look I don't really care what your mechanic says. I've been told enough
> guff by mechanics over the years to fill an encyclopaedia.



So you throw the baby out with the bathwater. They're ALL bad, right?



>
> The computer hasn't measured the mass of leaked air



It's NOT "leaked air". It's the very same air that has already passed by
the throttle plate and the air flow meter.

All the PCV valve does is make sure that flow is always present, and always
in one direction.

This is the part nobody in this group seems to understand. Of course,
nobody in this group is a working mechanic, either (me included). And some
of them aren't even willing to listen to what working mechanics have to
say.



>
> So your mechanics are right and the auto mfrs and engine designers are
> all wrong.<shrug>



Show me ANYWHERE where ANY auto mfr and engine designer says HOW MUCH the
engine will "run rich" with a plugged PCV valve.

I think you guys are all misunderstanding what those auto mfrs and engine
designers are saying. Web pages don't count here.



--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com

"Caroline" <caroline10027remove@earthlink.net> spake unto the masses in
news:mSNxc.8304$uX2.5993@newsread2.news.pas.earthl ink.net:

> "Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote

>
> For the rational among us trying to learn about pressure: Think of the
> crankcase as a bucket of water being fed with a hose but also having
> two holes in the bottom of it. The rate of water flow and the hole
> sizes are such that 4 inches of water are maintained in the bucket
> with this setup. If one suddenly plugs one of the holes, what happens
> to the water level in the bucket?



Bad analogy. Water is not air. Water cannot change density. That's why
hydraulics work the way they do.

You're wrong, Caroline. So completely wrong you have no idea how wrong you
are. Even George is clueless here.



>
> Forgot to add that various Chilton's manuals also comment on how a
> malfunctioning PCV valve may affect mileage. E.g. from the Ford
> Taurus/Mercury Sable 1986-1992 Chilton Manual:
>
> "Do not remove the PCV valve system from the engine,



You should learn to read. It says not to remove the SYSTEM, which is
definitely bad for the motor. The valve is only one part of that system.

--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com

"Caroline" <caroline10027remove@earthlink.net> spake unto the masses in
news:mSNxc.8304$uX2.5993@newsread2.news.pas.earthl ink.net:


> For the rational among us trying to learn about pressure: Think of the
> crankcase as a bucket of water being fed with a hose but also having
> two holes in the bottom of it. The rate of water flow and the hole
> sizes are such that 4 inches of water are maintained in the bucket
> with this setup. If one suddenly plugs one of the holes, what happens
> to the water level in the bucket?



A much more accurate analogy:

Imagine a bucket with ONE hole in the bottom (NEVER plugged). Now make two
holes in the SIDE, one above the other, but both always submerged. Connect
a hose between the two side holes.

THAT's your PCV system, minus the valve itself.


--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com

Tegger® wrote:
> "Caroline" <caroline10027remove@earthlink.net> spake unto the masses in
> news:mSNxc.8304$uX2.5993@newsread2.news.pas.earthl ink.net:
>
>
>>"Tegger" <teggeratistopdotcom@changetheobvious.invalid> wrote
>
>
>>For the rational among us trying to learn about pressure: Think of the
>>crankcase as a bucket of water being fed with a hose but also having
>>two holes in the bottom of it. The rate of water flow and the hole
>>sizes are such that 4 inches of water are maintained in the bucket
>>with this setup. If one suddenly plugs one of the holes, what happens
>>to the water level in the bucket?
>
>
>
>
> Bad analogy. Water is not air. Water cannot change density. That's why
> hydraulics work the way they do.
>
> You're wrong, Caroline. So completely wrong you have no idea how wrong you
> are. Even George is clueless here.

Maybe you guys should crosspost your discussion to rec.autos.tech and
see what some of the guys there say.

Are we talking a "Positive Crankcase Ventilation (PCV ) system. Nothing is
submerged or below any oil line. The PCV valve is simply a device that
meters the amount of air(crankcase vapour) the intake is allowed to suck
out of the crankcase, all well away from any pool of oil, and the other
hose is a supply of fresh filtered air being drawn into the crankcase ,
again above the oil, to replace the air that the PCV has drawn out.

"Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote in message
news:Xns9503EB8F64EB0teggeratistop@207.14.113.17.. .
> "Caroline" <caroline10027remove@earthlink.net> spake unto the masses in
> news:mSNxc.8304$uX2.5993@newsread2.news.pas.earthl ink.net:
>
>
> > For the rational among us trying to learn about pressure: Think of the
> > crankcase as a bucket of water being fed with a hose but also having
> > two holes in the bottom of it. The rate of water flow and the hole
> > sizes are such that 4 inches of water are maintained in the bucket
> > with this setup. If one suddenly plugs one of the holes, what happens
> > to the water level in the bucket?
>
>
>
> A much more accurate analogy:
>
> Imagine a bucket with ONE hole in the bottom (NEVER plugged). Now make two
> holes in the SIDE, one above the other, but both always submerged. Connect
> a hose between the two side holes.
>
> THAT's your PCV system, minus the valve itself.
>
>
> --
> TeGGeR®
>
> The Unofficial Honda FAQ
> http://www3.telus.net/public/johnings/faq.html
>
> How to find anything on the Internet or in Usenet Groups:
> www.google.com
> www.groups.google.com

"Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote
> "Caroline" <caroline10027remove@earthlink.net> spake
> > For the rational among us trying to learn about pressure: Think of the
> > crankcase as a bucket of water being fed with a hose but also having
> > two holes in the bottom of it. The rate of water flow and the hole
> > sizes are such that 4 inches of water are maintained in the bucket
> > with this setup. If one suddenly plugs one of the holes, what happens
> > to the water level in the bucket?
>
> Bad analogy. Water is not air. Water cannot change density.

The analogy has nothing to do with density. It has everything to do with mass
accumulation in a dynamic, fluid system.

BTW, water can change density. Indeed, in liquid pump calculations, the change
in density when moving a liquid such as water may have to be considered during
design.

non-rebuttal snipped

I have no problem with your unfounded opinion. But every time you spout here
that a malfunctioning PCV valve will never affect fuel economy, plan on facing a
rational explanation of why it may, along with a dozen or more citations of
greater repute than you, backing it up.

I too do not think much of putting out misinformation on Usenet.

"Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote
> "Caroline" <caroline10027remove@earthlink.net> spake
> > For the rational among us trying to learn about pressure: Think of the
> > crankcase as a bucket of water being fed with a hose but also having
> > two holes in the bottom of it. The rate of water flow and the hole
> > sizes are such that 4 inches of water are maintained in the bucket
> > with this setup. If one suddenly plugs one of the holes, what happens
> > to the water level in the bucket?

> A much more accurate analogy:

Nope.

> Imagine a bucket with ONE hole in the bottom (NEVER plugged).

= the breather hose (which is far far less likely to become plugged than the PCV
valve)

> Now make two
> holes in the SIDE, one above the other, but both always submerged. Connect
> a hose between the two side holes.
>
> THAT's your PCV system, minus the valve itself.

Presumably the level of water denotes the pressure of the gases in the
crankcase. (It does with my analogy.) Presumably in your version, the PCV valve
line is the hose connecting the two side holes.

Then you've got a PCV valve line whose intake is from the crankcase and whose
discharge is to the crankcase.

This is not the case for an actual PCV valve system. The PCV valve intake is
from the crankcase. Its discharge is to the air intake, very close to the
cylinders.

Your pressure relationships do not mimic those in an actual PCV system.

(PCV valve system here = the PCV valve and the hose from the breather chamber to
the PCV valve. This is the way many or all Hondas' PCV systems are set up. Other
cars' PCV hoses come off the valve cover.)

If you're going to consider this carefully, watch your mass flows, their phase
(liquid or gas), and when a chemical reaction (combustion) takes place to affect
pressure. Also, the fact that mass (air and fuel) enters the cylinders via the
intake valves but exits the cylinders via the exhaust valves *and* via blowby
past the pistons.

And since you loathe "Internet wisdom," here's Tom and Ray Magliozzi (yes, the
Car Talk guys), backing up what I have said:

-----
RAY: Blow-by occurs when combustion gasses slip by old, worn-out piston rings
and end up in the crankcase, where they don't belong. Actually, a small amount
of blow-by is normal and is easily expunged by the crankcase ventilation system.
But on old heaps (i.e., yours), worn-out rings can let so much stuff into the
crankcase that the ventilation system just can't handle it.

TOM: So the pressure in the crankcase builds up until gasses and oil try to
escape any way they can. And we often see air-filter housings full of oil, seals
blown out or leaking, and the occasional dribbling dipstick.

RAY: The solution is an engine rebuild, which would include a ring job. But
before you consider that route, or ditch the truck, I've got two other things
for you to try.

TOM: If you've lived a really good, clean life, your problem might just be a
plugged crankcase ventilation system. So have your mechanic check out your PCV
valve and the hose it's attached to. ...
-----
http://lang.motorway.com/home/articles/qandaoilydip.asp

Go ahead and knock two MIT graduates, both of whom worked in their own car
repair shop, and one of whom (Ray) has worked as an auto technician for some 30
years (and is still employed full time as such).

"Caroline" <caroline10027remove@earthlink.net> spake unto the masses in
news:BmSxc.8651$uX2.7052@newsread2.news.pas.earthl ink.net:

> "Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote
>> "Caroline" <caroline10027remove@earthlink.net> spake
>> > For the rational among us trying to learn about pressure: Think of
>> > the crankcase as a bucket of water being fed with a hose but also
>> > having two holes in the bottom of it. The rate of water flow and
>> > the hole sizes are such that 4 inches of water are maintained in
>> > the bucket with this setup. If one suddenly plugs one of the holes,
>> > what happens to the water level in the bucket?
>
>> A much more accurate analogy:


>
> Nope.


>
>> Imagine a bucket with ONE hole in the bottom (NEVER plugged).



>
> = the breather hose (which is far far less likely to become plugged
> than the PCV valve)


>
>> Now make two
>> holes in the SIDE, one above the other, but both always submerged.
>> Connect a hose between the two side holes.
>>
>> THAT's your PCV system, minus the valve itself.



>
> Presumably the level of water denotes the pressure of the gases in the
> crankcase. (It does with my analogy.) Presumably in your version, the
> PCV valve line is the hose connecting the two side holes.
>
> Then you've got a PCV valve line whose intake is from the crankcase
> and whose discharge is to the crankcase.
>
> This is not the case for an actual PCV valve system. The PCV valve
> intake is from the crankcase. Its discharge is to the air intake, very
> close to the cylinders.
>
> Your pressure relationships do not mimic those in an actual PCV
> system.
>
> (PCV valve system here = the PCV valve and the hose from the breather
> chamber to the PCV valve. This is the way many or all Hondas' PCV
> systems are set up. Other cars' PCV hoses come off the valve cover.)
>
> If you're going to consider this carefully, watch your mass flows,
> their phase (liquid or gas), and when a chemical reaction (combustion)
> takes place to affect pressure. Also, the fact that mass (air and
> fuel) enters the cylinders via the intake valves but exits the
> cylinders via the exhaust valves *and* via blowby past the pistons.
>
> And since you loathe "Internet wisdom," here's Tom and Ray Magliozzi
> (yes, the Car Talk guys), backing up what I have said:
>
> -----
> RAY: Blow-by occurs when combustion gasses slip by old, worn-out
> piston rings and end up in the crankcase, where they don't belong.
> Actually, a small amount of blow-by is normal and is easily expunged
> by the crankcase ventilation system. But on old heaps (i.e., yours),
> worn-out rings can let so much stuff into the crankcase that the
> ventilation system just can't handle it.
>
> TOM: So the pressure in the crankcase builds up until gasses and oil
> try to escape any way they can. And we often see air-filter housings
> full of oil, seals blown out or leaking, and the occasional dribbling
> dipstick.
>
> RAY: The solution is an engine rebuild, which would include a ring
> job. But before you consider that route, or ditch the truck, I've got
> two other things for you to try.
>
> TOM: If you've lived a really good, clean life, your problem might
> just be a plugged crankcase ventilation system. So have your mechanic
> check out your PCV valve and the hose it's attached to. ...
> -----
> http://lang.motorway.com/home/articles/qandaoilydip.asp
>
> Go ahead and knock two MIT graduates, both of whom worked in their own
> car repair shop, and one of whom (Ray) has worked as an auto
> technician for some 30 years (and is still employed full time as
> such).
>
>
>



--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com

"Caroline" <caroline10027remove@earthlink.net> spake unto the masses in
news:BmSxc.8651$uX2.7052@newsread2.news.pas.earthl ink.net:



Note to Caroline: This time, please do not remove the cross-posting. I want
as many minds involved in this debate as possible.




> "Tegger®" <teggeratistopdotcom@changetheobvious.invalid> wrote
>> "Caroline" <caroline10027remove@earthlink.net> spake
>> > For the rational among us trying to learn about pressure: Think of
>> > the crankcase as a bucket of water being fed with a hose but also
>> > having two holes in the bottom of it. The rate of water flow and
>> > the hole sizes are such that 4 inches of water are maintained in
>> > the bucket with this setup. If one suddenly plugs one of the holes,
>> > what happens to the water level in the bucket?
>
>
>> A much more accurate analogy:
>> Imagine a bucket with ONE hole in the bottom (NEVER plugged).
>
> = the breather hose (which is far far less likely to become plugged
> than the PCV valve)



You've got it backwards.

If our analogy is to be the bucket with a hole in the bottom, then the top
of the bucket is the throttle inlet and the bottom of the bucket is the
intake valve.

The PCV system has nothing to do with either the throttle or the intake
valve. It simply redirects some of the clean intake gas to the crankcase,
where it picks up blowby, and then directs it back to the intake again.

My anology (countering your erroneous one) has two holes in the side of the
bucket, both in the water, but one above the other with a hose connecting
the two. Absent the blowby, that IS a PCV system. It's just a redirector.

The PCV system does not go to a second intake valve, which is what you
conceptually imply with YOUR analogy of a bucket with two holes in the
bottom.

<snip>


>
> Your pressure relationships do not mimic those in an actual PCV
> system.



Neither do yours. Your bucket analogy consists of a non-compressible fluid
(water) being PUSHED into a container (bucket). The actual intake system of
a car uses a compressible fluid which is SUCKED into the engine.

The intake tract pressure is ALWAYS less than ambient with the engine
running. Hence, in a normal engine, there is ordinarily SUCTION at BOTH
ends of the PCV system. It is necessary to use a restrictor valve to lower
pressure at one end to make sure the flow is always in one direction.

That's the PCV valve.

Are you familiar with the venturi principle? That's all the PCV valve does.


>
> (PCV valve system here = the PCV valve and the hose from the breather
> chamber to the PCV valve. This is the way many or all Hondas' PCV
> systems are set up. Other cars' PCV hoses come off the valve cover.)



It doesn't matter. The principle is identical, even on carbureted cars:

Hose from intake to from crankcase -> Hose from crankcase to PCV valve ->
PCV valve back to intake tract again.



<snip>


>
> And since you loathe "Internet wisdom," here's Tom and Ray Magliozzi
> (yes, the Car Talk guys), backing up what I have said:



<snip quotes from TV personalities saying that heavy blowby will overwhelm
the PCV system>


Well, yes, all undoubtedly true. But this has never been part of the
discussion. What has any of that got to do with your contention of
reduction in gas mileage from a plugged PCV valve? The Car Talk guys
haven't said that at all.


--
TeGGeR®

The Unofficial Honda FAQ
http://www3.telus.net/public/johnings/faq.html

How to find anything on the Internet or in Usenet Groups:
www.google.com
www.groups.google.com