🚀 go-pugleaf

jmorriso@ee.ubc.ca (John Paul Morrison) writes (and draws a fancy picture):
> vanderby@mprgate.mpr.ca (David Vanderbyl) writes:
> >(This, incidentally, is why a hole in your muffler cannot help
> > you pass emissions testing.)
> 
> Depending on the shape of the hole, and its position, the exhaust gases
> could easily, and conceivably create a vacuum, and suck in more air into
> the hole, thus diluting the exhaust.

The point I was trying to make was that exhaust gases leaving the system
before the test probe does not give better test results, because the
quality of the exhaust gases is what is measured, not the quantity.

As to this vacuum theory, yes it is conceivable that fresh air may enter
the system.  However, it is extremely unlikely since the muffle/tailpipe
create a back pressure in the system.  This is why air pumps are necessary
for air injection anti-pollution systems, and the engineers who designed
the car cannot simply strategically place a well shaped hole to achieve
the desired effect.

-------------------------------------

kenb@ee.ubc.ca (Ken Buckland) writes

> [a vacuum hole] does not help you however because their testers pick up the extra air
> in the exhaust and conclude that you have holes in your exhaust system.
> This is what happened to me. 

While it is true that the test probe would pick up the extra air, this
would result in the tester thinking you car has low emissions, not that
you have holes in your exhaust.  (Some cars actually have fresh air
injection, are they failed for holes in their exhaust?)  This may be the
reason that any hole in your exhaust results in a failed test (if they
see it, that is.)

Dave.