Date: Tue, 1 Dec 2009 10:43:45 -0800
Reply-To: neil n <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil n <musomuso@GMAIL.COM>
Subject: Re: info needed on crancase ventilation systems (mostly I4)
In-Reply-To: <vanagon%2009120102125602@GERRY.VANAGON.COM>
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On Mon, Nov 30, 2009 at 11:04 PM, Sam Payne <bungeegull@hotmail.com> wrote:
> Hi,
>
> I've been away from the list and my van for awhile but am finally
> getting back into both.
> I have an '86 westy which I put an inline 4 into (2 liter Audi 3A)
> run by a Bosch Jetronic fuel injection system, based on excellent research
> done by Frank Grunethaner (see my previous posts).
> The van drives and I'm quite happy with it, but the crankcase
> ventilation system as I plumbed it collects too much oil (engine
> compression is perfect), so I'd like to modify it. The problem is that I
> think I see several different ventilation strategies out there, but am not
> getting it entirely. If you know, please help!
> I've looked at crankcase vent strategies in VWs, Saabs, and BMWs in
> the junkyard and think I see two basic methods:
>
> 1.) fresh air is pulled in to vent the engine from a breather hose
> running from a connector between the AFM and the throttle plate to the
> valve cover, and blow-by is vented from the engine by a hose running
> between the valve cover and the intake manifold. Saab does it like this.
>
> 2.) On most VWs the vent seems to be just a hose running from the
> valve cover to the air filter, with a large PCV valve at the valve cover.
> No fresh air seems to be drawn in. S'up with THAT?
>
> I don't understand the operation/benefits of each method,
> specifically:
> 1.) In method #2, why is no fresh air drawn in? Is it enough to vent
> blow-by only? Wouldn't that be less effective, especially for venting
> moisture?
> 2.) Why do some systems have no PCV valve? How do they regulate
> vacuum, specifically the high vacuum at idle?
> 3.) What method best fits a LH Jetronic FI system, which uses an air
> mass meter.
>
> My engine has two vent points: the valve cover, and the side of the
> block below the cylinder head water input. Most VW I4's have the block
> vent blanked off. Can I do that?
> Or, should I input fresh air into one vent and output blowby fron the
> other, more like the Saab method?
> Or, should I connect the vents and run them through a pcv valve and
> down to the air filter?
>
> Many thanks for any help, Sam Payne
>
Here's how my 2.0 Jetta engine is vented:
Block vents to/through PCV on valve cover, to intake bellow between
AFM and throttle body. If it were me, I'd stick with whatever is stock
for your engine.
FWIW, I found that 3/4" copper pipe, galvinized nipple, short bit of
rubber hose + clamps works fine to interface PCV to intake bellow. I
can't recall exact details, but can take better pics if this applies
to your engine.
Pics below show general idea though you have to look closely. It looks
different than stock, it is vented as per stock. You can see the green
clamp connecting pipe from block to PCV, then from PCV to intake
bellow. I would guess that your Audi engine is the same or very
similar.
It works fine, though I have yet to check if oil is pooling in bellows
near AFM. I have read that on the stock Mk3 Jetta, oil can foul the
AFM over time. Since my air cleaner is lower than stock, I figure this
might be an issue. Likely not though as air is being pulled away from
AFM. Time will tell.
http://tinyurl.com/ychhxol
http://tinyurl.com/yajdjvv
Neil.
--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"
http://tubaneil.googlepages.com/
http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
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