The way the limits are set is as follows. EPA publishes a large table
of emission limits for each component (HC, CO and NO). Each table has
limits by vehicle weight and standard. For example 68-72 vehicles can
emit HC at standard 13, 73-74 are also limit 13, 75-76 and 77-79 are
limit 11 and 1980 is limit 4 (these are first year phase in for HC).
There is another table that list the test weight for each vehicle made.
The MGB is listed as 2,500 until 1977 then its 2,750. This is a test
weight. Using the limit and the test weight the allowable emission can
be determined.
When 1980 vehicles have to much cleaner than earlier ones for several
reasons:
1) they are newer so there is less deterioration of the emissions system
2) the new standards were tighter (not sure here I know 1981 were much
tighter than previous standards)
3) The limits are set to have a certain number of vehicles fail so they
can be fixed and air quality improved. Its possible that vehicles made
in 1980 and later stay cleaner (due to wider use of EFI) so that tighter
standards are possible with out a horrendously large failure rate.
Pat what were the pass fail limits on your test?
Patrick Bailey wrote:
>
> >Oops one other thing,why is the limits so much less for the 80 B?
> what is different from the 79?
> Pat
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