Spark Exhaust dB Killer Hot Road 35 mm 12 Holes Universal G9977

Twelve holes — the fewest of any Spark insert — through a thirty-five millimetre bore. The Hot Road case gets an insert of its own because nothing else in the range shares its outlet.

Key Features

• dB killer for Spark Hot Road silencers.
• Ø 42.7 mm outer, 35 mm internal bore.
• Perforated: 12 holes.
• Stainless steel, removable.
• Spark part number G9977, made in Mantova, Italy.

A Narrow Body, a Wide Bore

Forty-two point seven outside, thirty-five inside. That is an unusually thin annulus — less than four millimetres of wall and perforation all the way round — and it is what the Hot Road's outlet geometry allows.

It also explains the hole count. There is not much surface to put holes in, so Spark used twelve larger ones rather than the twenty-eight small ones it puts in the round-case inserts.

Made for the Cut Outlet

The Hot Road ends in a long diagonal slash rather than a square cut, which means the insert seats against an oval opening rather than a circular one. That is why this article exists as a separate number instead of sharing with the vintage cases.

Left-hand and right-hand Hot Road silencers take the same insert. The case is mirrored; the outlet section is not.

Twelve Holes, and What They Do

Fewer, larger holes attenuate lower frequencies less and higher ones more than many small ones would. On the kind of large-capacity twin a Hot Road usually ends up on, that keeps the low note the owner bought the exhaust for while taking the hard edge off the top.

Not Supplied With the Silencer

Unlike Spark's vintage cases, the Hot Road universal silencers are not listed with an insert included. If you are ordering a Hot Road and expect to need noise control, add this article to the same order.

Left and Right Take the Same Part

Spark builds the Hot Road as a mirrored pair, G00SI18I and G00SI19I, but the outlet section is common to both. A build running one of each needs two of this insert, ordered as the same number twice.

Approval

The Hot Road carries none and neither does this. It is a noise part for circuits and for making a loud custom bearable, and it makes no difference to what an inspector sees on paper.