Which Weber Carb would be most suitable for the Nissan 1400 Bakkie engine
if WOT vacuum is near (not at) atmospheric pressure then the
Cab is not undersized.
you do know oversized carbs can never be tuned , right?
the carb can only deliver more fuel mix, and make more power
if the engine can breath more air.
so we do vacuum tests to see if a bigger carb can help.
on most cars , no.
1.4L is a small engine. and can be very easily over carb'd
I use a baro gage, (Sensor) and key on not started, is my
Atmospheric pressure, it will be 0 pressure. (absolute)
14.7 psi 0 abs pressure, at sea level.
i start the engine and see idle pressure. (near max)
i wide open throttle the engine, up a hill and see if it drops near 0
but not zero, the carb will stall near zero.
the venturi fails there. hard.
to learn this , read the full spec. on your carbs. see the spec
for minimum pressure drop to to bottom.
there must be X drop or the carb stalls.
The carb fuel nozzles, die of near this point and can not be tuned.
one great exception to this is CV or SU carb, they adjust automatically to this pressure.
Think of this one other way.
The engine pumps air (end to end, carb removed.
what is that CMF,(cubic feet per minute)
buy a carb to match that.
there are great free computer models to do that.
Mar 23, 2013 |