Kenneth Scott <KSCOTT@holycross.edu> wrote:
"The basic frustration is with the attitude "I don't care whether it
makes
emissions specs or not, it ain't stock so it don't pass". This is
blatant
stupidity. If certain emission limits are set and my car passes these
it
should not matter what is under the hood. This is called being
reasonable and logical. We are dealing with government here and
government is not known for being reasonable or logical."
The drive through smog test is a bad compromise. Before any car can be
sold in the US or California a sample vehicle must be driven on a
dynamometer and emission tested. The results of this test is expressed
as grams/mile of different emissions (unburnt fuel, carbon monoxide, and
nitrogen oxides). The manufacturer had to guarentee that the cars they
sold would meet these requirements for 50,000 miles (since increased to
100,000 miles).
For reasons of cost, test time and test difficulty annual (or bi-annual)
testing was limited to idle tests. Limits were chosen (in ppm) that
would show vehicles with poor emissions equipment. Because the test is
only run at idle it is quite possible to pass this test while still
being a gross polluter under other modes of operation (while driving
under load). In order to limit this possibility the politians required
that all of the orginal equipment be installed.
The emission systems on LBCs were not well thought out (to say the
least) this makes it difficult to pass any emission test even with all
operating equipment. MGB intake design has large flow through the front
port then high flow through the rear (firing order 1342 or written
another way 3421, two rear cylinder pulling in air then the front two)
this causes cylinders 3 and 2 to run lean and 4 and 1 to run rich.
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