By Wayne Scraba
NOT too long ago mufflers were
considered a necessary evil with the
performance crowd (that’s definitely
us). Noise equalled power. Or at least,
that was the general train of thought
and of course, racket reigned supreme.
You couldn’t have a hot rod without it.
On the flipside though, a quiet exhaust
system certainly does have a number of
positive attributes: For example, it keeps
your ears from ringing incessantly,
it promotes friendly relations with
your neighbours (more or less), and
equally important, it doesn’t attract
added attention from you-know-who.
All good news we’d have to say.
Unfortunately, many original
equipment production-based muffler
configurations (along with most
inexpensive replacement jobs) also
soak up valuable horsepower. That’s
probably no secret to anyone reading
these pages. Other than keeping the
noise down to a dull roar, the main
objective of an exhaust system is to
“cleanse” the combustion chamber
during the exhaust stroke. This “blow
down” creates the ideal environment
for the fresh air-fuel charge to be
introduced into the chamber during
the intake stroke. Clean out the
combustion chamber efficiently, don’t
plug up the exhaust and you make more
power. That’s the basic concept. But
the reality is you can also make plenty
of unwanted commotion (of the big
decibel kind) if you’re not careful.
How do clean out the combustion
chamber, maintain decent flow through
the exhaust and still keep things
quiet (and legal)? It’s not that easy
-- especially when high performancecars are concerned, but today high
tech exhaust system manufacturers
such as Hooker Headers have a number
of equally high tech answers.
Seriously not much can outflow a
straight section of pipe. The trouble
is, an open section of pipe does little
when it comes to the sounds of silence.
One type of exhaust “silencing” which
was once overlooked is absorption
technology. When you first think
about “absorption” mufflers, you
automatically recall the old straight-
through glass pack setups. They’ve
been available forever. In practice, a
glass pack includes a pair of tubes --
one inside the other. The inner tube is
punched with louvers and sandwiched
between the tubes is a packing material
(almost always made from fibreglass).
As the spent gasses pass through the
muffler, the sound (or at least some of38 > NZ HOT ROD AUGUST 2019
Today, aftermarket manufacturers such as Hooker Headers go to great lengths to produce mufflers and
exhaust systems which out-perform OEM pieces. Case-in-point is this trio of mufflers from Hooker Headers.