Spark Exhaust Stainless Steel Tube Ø 70 × 1.2 mm 500 mm Universal G9009

Seventy millimetres, and the first step up in wall thickness since the twenty-eight. At this size a tube stops being a pipe and starts being a body.

Key Features

• Straight exhaust tube, AISI 304 stainless steel.
• Ø 70 mm outside, 1.2 mm wall thickness.
• 500 mm long.
• Thicker wall than the 32 to 60 mm sizes.
• Spark part number G9009, made in Mantova, Italy.

Why 1.2 mm Here

A one millimetre wall is entirely adequate for stiffness at seventy millimetres. What it is not adequate for is noise: a large-diameter thin tube radiates sound through its own wall, and past sixty millimetres that becomes audible as a metallic ring layered over the exhaust note.

Two tenths of a millimetre of extra wall raises the panel's natural frequency and damps it. It is a small change with a disproportionate effect.

What Gets Built From It

Silencer bodies, pre-silencer boxes, expansion sections and the large-volume chambers that a custom system uses to control noise without a restriction. Seventy millimetres is rarely a gas path in its own right — it is the shell around one.

Rolling an End

If you are making a silencer body, the ends have to close. That means either a spun cap, a rolled edge or a machined end ring, and all three are easier at 1.2 mm than at 1.0: thicker material tolerates being worked without splitting.

Weight Goes Up Fast

A 500 mm length at 70 × 1.2 weighs close to a kilogram. Diameter and wall both count, and at this end of the range the material becomes a real part of the finished weight rather than a rounding error.

Bends

Spark bends this diameter at 30°, 45° and 90°. Bending 70 mm at home is not realistic without proper tooling; the wall will collapse on the inside of the radius long before the tube reaches the angle.

Perforated Core, Separately

A silencer body built from this tube needs a perforated inner tube and packing to be a silencer rather than a resonator. Spark does not sell either as a catalogue article, so plan that part of the build around what your workshop can source — the outer shell is the easy half.

Ordering

One 500 mm length per article, supplied uncut.