Spark Exhaust Bent Tube 30° Ø 42 × 1.0 mm Stainless Steel Universal G9120

Forty-two millimetres through thirty degrees. The odd size, in the shallowest angle — a bend bought when a factory system measures something other than a round number.

Key Features

• Mandrel-formed 30° bend, AISI 304 stainless steel.
• Ø 42 mm outside, 1.0 mm wall thickness.
• Slides over 40 mm tube as a sleeve.
• Matches Spark's 42 mm straight tube, article G9008.
• Spark part number G9120, made in Mantova, Italy.

The Size Between the Sizes

Most suppliers stock forty and forty-five. Original-equipment exhausts do not confine themselves to those, and a factory pipe measuring forty-two is common enough that Spark keeps the size in the range.

Matching exactly beats adapting. Two millimetres is around ten per cent of flow area, and it also saves a transition piece.

A Bend That Is Also a Sleeve

Forty-two outside with a one millimetre wall gives forty inside, so a 40 mm tube slides straight into the end of this bend. That turns the joint into a slip fit rather than a butt weld with no machining at all.

It is a useful property of this specific diameter and it makes the bend worth having in a rack even on a project built entirely in forty.

Ovality at the Tangent

The section is most likely to be out of round just where the curve meets the straight. On a mandrel-formed bend that deviation is small, but it is where a slip joint binds if the fit is tight.

Check the end with a vernier across two axes before assuming a sleeve will go on.

Fitting Into a Sleeve

If this bend is going into something larger, chamfer the outer edge of the cut end. A square-cut edge catches on the sleeve and picks up a burr on the way in, and that burr is what stops the joint separating later.

Two Bends, One Offset

A pair of 30° bends welded opposed with a short straight between them moves a run sideways without changing its direction. How far it steps depends only on the length of that straight, so one pair of bends covers a wide range of corrections — the standard answer to a silencer sitting a centimetre off where it should.

Ordering

One bend per article. Spark makes 30°, 45° and 90° at forty-two millimetres.