The Garage 266

23
ANALYSIS
ent designs including round
and flat catalysts. During
manufacture of a round
catalyst, an I.O. swaging machine
is used to perfectly size
the internal diameter of the
outer metal can (also known
as the mantle). This process
ensures the correct gap is
achieved, between the inside
of the can and the monolith,
therefore giving the optimal
holding force on the monolith.
This gap is where the
matting collects. The matting
is designed to provide
just the right density to nullify
the differences between
the metal can’s thermal expansion
and the monolith.
Using the correct matting
density is essential to avoid
loose and rattling cats (when
too low) as well as cracks in
monoliths (when too high).
The matting used in BM
Catalysts products is also
designed to have a lower
erosion profile compared to
traditional expanding mats,
and is certified as a Class-
Zero, True Green Support
Mat System; meaning it is
safe for their staff and other
handlers of the product as it
contains no Refractory Ceramic
Fibres (RCF).
The remaining components
of a cat are present
mainly to ensure secure fit
to the vehicle. The pipework
sections are also made from
409 grade stainless steel
tube. This particular material
is suitable for pipe sections
due to its malleability,
strength and corrosion resistance.
Pipes are cut, bent
and sized on hi-tech CNC
machinery, ensuring consistent
production accuracy
and O.E. standard air flow.
Flanges, lambda bosses,
brackets and other fittings
are the smaller components
which provide the finishing
touches to the cat, and furthermore
assist in determining
the exact fitment of each
unit: Flanges, which join the
cat to the next section of the
exhaust, are manufactured
on seven metre long CNC
plasma cutting beds. The
plasma ‘cuts’ each individual
flange into shape, then
the component undergoes
the required drilling, threading
and machining on a CNC
Milling Machine, dependent
on the required finish specification.
The lambda boss
sensor ports are produced
on CNC lathes which run for
24 hours a day. The lathes
automatically feed solid bar
through the cutting, sizing
and threading process.
Brackets, like flanges, are
plasma cut into shape into a
2D profile, and then folded
to the required form by a
CNC Press brake.
A maniverter catalyst
would also involve a manifold
section, which allows
the unit to be bolted straight
onto the engine cylinders.
The manifold component is
made up of a number collectors/channels
which transport
the gasses from the
engine cylinders to the catalyst.
A four-cylinder engine
will require a four-branch
manifold.
Maniverter catalysts and
close coupled catalysts are
designed to allow the gas
conversion to take place
close to the engine; where
the gasses are at their hottest,
and therefore where the
conversion is most efficient.
Over the years, emissions
standards have become increasingly
stringent, which
has led to the catalyst section
– containing the monolith,
matting and precious metals
– being located closer to the
engine (on maniverters and
close coupled cats), than on
underfloor-style cats.
As emissions standards
continue to become tougher
to reach, vehicle manufacturers
are now starting to
put additional catalytic converters
onto their vehicles to
ensure limits can be hit. Vehicles
that used to have one
catalyst on for Euro 4 level
are now sometimes having
two fitted for Euro 6 levels.
To watch a video of a BM
Catalysts catalytic converter
being manufactured, visit
www.bmcatalysts.com. Further
information on catalysts
and tips how to look
after them can also be found
here, or request a BM Technical
Poster by emailing
marketing@bmcatalysts.
com.
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