PCV VALVE... Really?

[romantic comedy]

A misfiring engine will allow raw fuel to pass through the exhaust too. I keep thinking that the ignition is suspect.

I also wonder how one feels that an engine is running rich.

When we have a pcv valve it is not necessarily a steady air leak. These pcv valves are not perfect, and may be intermittent.

A post a few back, mentioned the spark plugs were toast. What specifically was wrong with the plug?

I know there are sensor that can tell the mixture. I am surprised that these have not been brought up yet.

[joe_db]

It isn't easy to use an O2 sensor on a wet exhaust engine. You have to drill and tap a hole in the manifold.

[ndutton]

Hanley has an oxygen sensor and likes it. He uses it to provide information, not part of an integrated fuel management system.

[Ball Racing]

I think for good numbers,
we should try a vacuum gauge on the manifold,
and one placed close to the pcv valve as well.
Then you can see just what a leak is present at different throttle positions and be able to compare one area of pull to the other at the same time.

[ndutton]

In addition to vacuum measurements I was thinking Hanley's oxygen sensor arrangement would be a good tool but it's a long way to go to satisfy curiosity. It's not like engines are shutting down.

[sastanley]

What's wrong with crop dusting?

I am not pulling my engine for a rebuild until absolutely necessary!

[romantic comedy]

I use the vacuum access on the manifold for everything. You dont need that plate between the carb and manifold.

[Sony2000]

The best PCV valve for me is one that remains closed under its weight at idle,but starts to open as the. RPM rises from the vacuum of the manifold and the push of the blowby. It's a balance and one size does not fit all. One PCV isn't for every engine.

[ndutton]

I'm still watching for a single post suggesting the engine benefits in any way by adding a PCV system.

[Sony2000]

An answer can be, that the absence of a "firewall" prohibits engine consideration, and endorses a PCV system.

[romantic comedy]

There is no benefit to the engine. It is an emissions control device. The benefit is for the atmosphere. Which is the reason that we use it on the Atomic Four.

[Ball Racing]

Any engine performs better with a vacuum pulled on the crankcase.
It causes better ring seal, cuts down on oil useage, which in turns make more hp not burning oil.And of course better ring seal make more hp.
Many many race engines pull vacuum on their bases.

Some pull it using the exhaust, some have external pumps etc.

You should see the "reed" valve set-up that ARC company made for the briggs & stratton motors flatheads I used to race. Very complex system to form a vacuum on the base.(without the use of a pump)
So I have seen the benefiet, and thats why I have still been wanting to use it.
I am just not sure of the amount of vacuum if any we can have in our base given the front lack of seal arrangment.

This is one thing that is hard to want to use, until you know alot about motors, and these type of devices, and have run them, tuned them and had them on a dyno getting number.
I am no rocket scientist, but I did mess with engines enough to know there are better mouse traps.
But me getting that across in terms to people who are not as familar ,is hard
and makes me look silly trying to sell it.
I know that this A4 is not a typical car or any other race engine.
But R&D from other forms can applied in some cases.
Will the A4 respond?
I like some others have no proof from trying it yet.

[Sony2000]

[QUOTE=Ball Racing;62309]
I am just not sure of the amount of vacuum if any we can have in our base given the front lack of seal arrangment.

Given this situation, I have tried to limit air entering the oil filler access, then will add the PCV this summer. The blowby will then have only two places to go. The front seal or the PCV system.
The engine may develop a too lean issue and require a richer mixture that certainly won't be optimal due to an inconsistent fuel/air mixture. Not much new there.
And if the cabin smells of fresh sea air, as a result, I will have championed the cause.

[ndutton]

In consideration of four decades of respectable performance without a PCV I look at it like this:

Let’s say your raw water cooled engine rusted a hole through the water jacket side plate and while running, water was leaking out. The water pump is supplying plenty of water to keep the engine temperature in check. What to do, fix it or manage it? Solve the real problem by replacing the water jacket side plate or add a bilge pump and leave the leaky plate in place?

I also think given the vented oil fill cap the lack of a front crank seal is small potatoes.

[Sony2000]

How about, carbon monoxide as being odourless and lethal, for a good reason?

[Ball Racing]

Okay,
"I" am aware,maybe not all others, that a rebuilt- new engine will not have a mushroom cloud of smokey blowby.
So if the owner's sole one purpose of a PCV would be to rid the cabin of a stinky mess, instead of doing alittle maintaince is not sound judgement.

But "my" engine is a fresh one.And I still see a advantage until proven wrong.

And if my point is even being considered,
who among us are soley waving placards against rebuilds?

I feel on this I am just banging my head against a wall,
and I am not sure if it's from the people who don't want to do maintainace,
or those who choose that me and them are wrong.
Kinda guilty until proven innocent.
And I can't make it to the boat to try things because I keep getting called back to the courtroom to defend myself.

[ndutton]

I'm not trying to get anyone to change and I know I'm standing alone here. What I've asserted is what applies to my boat. Daniel, you are the first one to suggest there's a performance advantage with a PCV and I expect you'll be plugging or restricting the fill pipe cap to achieve the crankcase vacuum you mentioned and therefore reduce the unmetered air flow into the manifold via the PCV in the process. I think we can agree the vast majority are using it to mitigate blowby gases.

I'll repeat, on my boat in my little corner of the world blowby that can no longer be managed by the factory original slash tube is an indicator of internal engine wear. When the time comes I'll choose to address the root problem (wear) rather than mask the problem (PCV). That was the point of my sideplate story.

I'll choose not to deal with carb adjustment difficulties and choose not to install an adjustable main jet to compensate for the PCV. I'm happy with the way things are and will strive to keep them that way.

May I assume you'll not be interested in my new line of logo apparel?

[Ball Racing]

Yeah, I will take a couple
I told you I was willing try things.

[joe_db]

FYI - I did an interesting experiment today. At *idle* the PCV valve does not much one way or the other. I had tried that before. At about 1200-1400 RPM it has much more effect. Pinching the hose off gains at least 2" vacuum and the engine loses at least 200 RPM.

[roadnsky]

Originally Posted by romantic comedy

A post a few back, mentioned the spark plugs were toast. What specifically was wrong with the plug?

What I posted was...
"I first tore the carb down again to make sure it was clean and I put in new plugs.
The current set were distinctly sooty"

They weren't toast. The engine was running well with them in.

[roadnsky]

Originally Posted by romantic comedy

...The thing that I cant get, is how can a vacuum leak cause a rich condition.

Here's something to think about...

Today I took some fuel down with me. I carry about 4.5 gal in a 5 gal can.
When I went to pour it in something occurred to me...
I usually add some MMO every time I add fuel.
Hmmm, I wonder if that could be what is "burning" that I'm interpreting as too rich?
Hmmm...

(So, for this fill-up I didn't add any)

[Ball Racing]

Yeah, I have always been adding ALOT of MMO, and if I am just cruising around and engine doesn't see much load or temp,,,,
She will smoke off the MMO upon a hard rev, and you can smell it along the way.
I have cut back on the MMO and have seen-smelled less.

[romantic comedy]

Clarification:
Roadnsky, this is what I was referring to. I should have been more specific.

Originally Posted by jstoehr

Some 10 or 11 years ago I installed Indigo's PCV kit and had some interesting results. Being that long ago I can only think that I thought I had a blow-by condition, but probably just thought that it was a good idea. On a long trip following the installation the engine ran absolutely fine except that after, say, 3 hours of motoring the A4 just didn't sound right. After two long motoring days the motor refused to start on the third. No spark. Since the plugs were new I focused on wires and coil while my wife insisted I pick up some new plugs just in case. ( I had also installed Indigo's electronic ignition kit.)

After trying all the other stuff I bought and getting nowhere I just threw in the new plugs. It started right up. Two days later those plugs were toast. It took me two more sets to get me back home. One thing I noticed was that paint in the wells in the head around the plugs had burned off.

I queried the Sailnet A4 list and got a couple post suggesting I was running too lean and that I could fry the engine if I didn't do anything about it. One post came from Qshicks - any of you remember him? One of the most intuitive motor guys I've ever run across. He got me to put in an adjustable main jet in the carb and I could finish the season with one set of plugs.

What's this got to do with PCVs? They are designed to draw crankcase air into an adapter added between the carb and the manifold, which is a way of adding air to the mix after the supposedly correct mix coming from the carb, thus leaning it further. I'm wondering if the corrected richness at the start of this thread came from the addition of the PCV.

I also use MMO in the gas, and the engine smokes. I think that I probably use too much MMO. Maybe it is crankcase oil, I dont know. The compression is 125 in each cylinder, but I have plenty blow by.

[roadnsky]

Originally Posted by romantic comedy

Clarification:
Roadnsky, this is what I was referring to. I should have been more specific.

Ahhhh, my bad. Makes sense now.

I also use MMO in the gas, and the engine smokes. I think that I probably use too much MMO.

I'm starting to think the same thing. Could explain my "rich" conditions...

[edwardc]

Originally Posted by joe_db

It isn't easy to use an O2 sensor on a wet exhaust engine. You have to drill and tap a hole in the manifold.

Actually, the Moyer manifolds have an exhaust flange on both ends. This allows them to accomodate both "nornal" engines and "backward" ones that have a V-drive with a single part. The unused flange is closed off with a flat plate.

This makes it really simple to add an oxygen sensor to an A4 with a Moyer manifold. The flange plate can be removed and drilled & tapped in the comfort of your home shop. I even bought a separate plate to drill out, so the conversion can be easily reversed if that's ever needed.