I just finished another round of testing/modifying the
emissions re-circulation, while relieving the crankcase
pressurization problems of our LBC.s
Recent experiments led to running a full manifold
vacuum tap right down into the crank case. To limit
'physical' modifications for testing, I simply inserted
a Mityvac vacuum canister in the ckt, and plugged the line
into the dipstick tube. I used an adapter, and stepped
up the hose ID to 1/2", four foot long, and attached it
directly to the intake manifold tap. The vacuum gauge
reading right at the dipstick tube 'hovered' around
5-10 in/Hg vac. While ';throttling up' the pressure in the
crank would rise enough, as well as the delay through
the tube, of the vacuum falling, seemed to smooth
the rate at which the engine saw the pressure changes.
This pressure change was 'note-able' by simply watching
the WBo2 sensor meter (accurate/repeatable to 0.2 A/F)
and how quickly, if at all, it changed.
At sudden throttle change (remember ZS carb dashpot oil
limits mechanical 'rate' change of fuel/air ratio) I could see
the WB02 swing from the nominal 14.2 at idle (info taken
from an old Vintesse manual) to 15.4 as the vacuum
disappeared and pop right back to nominal.
I barely got any oil in the vac tank (clear plastic) except
at high revs so my somewhat universal mount separator
design will work :-)
NOW THE GOOD NEWS....
With the vacuum at 10 in/Hg in the crankcase.... the vac/pressure
gauge up in the 'rocker cover/carb/carbon canister' hosing,
never saw any pressure. I only ever saw the needle on the gauge
'flicker' towards the vacuum side from zero.
So...I'll be making up a proper breather port for the crankcase.
the current 'model'
breather/oil separator canister (catch tank) is/will be
something like the 1275cc A-series MG engine
mounted on the timing chain cover. This is plumbed directly
to the carb side breather ports. This same crankcase
breather facility on the MG B series engine is a pipe on the
cover of one of the tappet chest lids that bolt onto the side
of the block.
The difference here is the Midget oil cap has a breather hole,
the B is a sealed cap. The B rocker cover has vent that
taps the carbon canister as the 'input' of air to the crankcase,
while the A-series used the hole in the oil cap.
ROUTE1
route the crankcase breather directly to the carbs, with the
rocker cover tapping the 'big' port on top the carbon canister
(like the MGB) . The fuel tank and carb bowl vents will stay stock
on the carbon canister
....So this would suck fumes back into the engine through
the engine, back to the intake.
ROUTE2
route the crankcase breather directly to intake manifold, with the
rocker cover as originally configured That being the carb intakes,
rocker cover vent and carbon canister all breathing directly together
through the 'big' port of the carbon canister..
SO THE MAIN POINT WAS...
No more crankcase pressure blowing oil out through all the seems.!
Paul Tegler
ptegler@cablespeed.com
www.teglerizer.com
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/spridgets
|