Date: Wed, 3 May 2006 00:49:45 -0400
Reply-To: "Daniel L. Katz" <katzd54@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "Daniel L. Katz" <katzd54@YAHOO.COM>
Subject: Re: idle and black tower
list:
modification worked wonders for '84 idle, overall running, and power. here
is the current iteration:
from exit of black tower:
short 3/4" heater hose inside of which is pushed (snug fit) a modified pcv
valve**, pintle side away from tower
3/4" to 5/8" reducer (would use 3/4 to 1/2 inch if i had one handy)
length of 1/2" hose making loop back and around toward intake maifold
short molded 1/2" hose at manifold removed and replaced by short straight
piece followed by original "y"
connected looped 1/2" hose and also vacuum line for charcol canister
to "y" (i had to extend line for charcol canister slightly, using ordinary
rubber vacuum hose)
i left the auxiliary air regulator out of the system for now. if future
problems, it can be integrated with a "t" fitting, although it is pretty
tight in there.
the two intake ports, from auxiliary air regulator and original 3/4" hose
from black tower, are plugged.
i adjusted the idle control screw (really an air bypass) all the way in,
and trimmed the idle/O2 sensor output using the co adjusting screw
end results:
approximately 880 +/- 30 rpm idle; O2 output .55 +/- .15 V
added bennefit: certainly lower crankcase pressures and therefore LESS
danger to seals from blow-by pressure.
**throttling blow-by through pcv valve yielded a more stable idle than
wide open operation, and probably helps with oil control as well (no blue
smoke). additionally, the pcv valve will close in response to a front-
fire propogating back toward the black tower, thus protecting against a
possible crankcase explosion (less of a danger here than in a true pcv
system due to relative lack of oxygen).
pcv valve was modified by slightly crimping the housing on the pintle end
to prevent the pintle from moving past point of maximum open, thus
avoiding the possibility of valve closing too much at high manifold
vacuum, which would cause blow-by pressure to build up in the unvented
crankcase (which could cause oil to rise up dip stick tube, perhaps blow
seals, and etc). pcv valve action is otherwise normal.
dan
On Sun, 30 Apr 2006 00:45:16 -0400, Daniel L. Katz <katzd54@YAHOO.COM>
wrote:
>list:
>
>i re-routed blow-by direct to intake manifold, essentially with a T
>fitting on the vacuum side of the auxiliary air regulator. engine seems
>very contented with this fix, and idles well. preliminary verdict is that
>idle problem is fixed, and blow-by is properly handled. also, lower
>crankcase pressures should lower air resistance to moving pistons, and
>provide a slight edge in terms of overall efficiency.
>
>a future project may be to vent the engine to the atmosphere via one valve
>cover, and install a pcv valve bewteen black tower and intake manifold,
>essentially converting to a true positive crankcase ventillation system.
>this would certainly be a plus for the engine oil, and otherwise help
>limit gum and sludge. a blow-by/air mixture is much more combustable than
>blow-by alone, however, and so the action of the pcv valve to block
>possible front-fires from propogating into crankcase via black tower is
>necessary. worry here might be that the restricting action of the pcv
>valve combined with an inadequately vented engine could lead to high
>crankcase pressures, under certain conditions at least, resulting in all
>sorts of problems, and i'll probably just leave well enough alone.
>
>looking at long ago posts, the black tower certainly has baffles - perhaps
>also a flapper valve of some kind that is usually destroyed on older
>engines; i've never taken one apart myself.
>
>all's well that idles well!
>
>dan