Akrapovic Slip-On Line Titanium BMW K 1600 GT / GTL (2011-2024) – S-B16SO4-HZAAT

A straight six is the rarest engine in motorcycling and the one that responds best to an exhaust, because there is nothing else on the road that sounds like it. Akrapovic's Slip-On Line (Titanium) S-B16SO4-HZAAT for the BMW K 1600 exists to let that engine be heard — and it takes 3.3 kg off a touring bike at the same time.

Key Features

• Built for BMW's 1,649 cc straight six, with the sound work aimed at making long distances more enjoyable rather than louder
• 8.4 kg against the standard 11.7 kg: 3.3 kg and 28.2 per cent less
• Titanium construction with carbon fibre outlet caps
• 2.7 Nm more torque at 5,600 rpm and 2.3 PS (1.7 kW) more power at 5,870 rpm — both gains sit in the touring rev range
• Peak torque 161.4 Nm against the standard 159.9 Nm
• Compatible with the BMW side cases, so a fully equipped GTL keeps its luggage
• EC and ECE type approved with certificates supplied

Sound Engineering for a Tourer

Akrapovic states that the engineers introduced further sound enhancements specifically so that long trips become enjoyable sound experiences. That framing matters: on a machine built for eight-hour days, a system tuned for maximum volume would be a mistake. The work here went into the character of the six rather than its level, and the exhaust stays inside the type-approval window.

The design is unmistakably Akrapovic and unusually restrained, in keeping with a bike that is more Gran Turismo than superbike. The outlet caps are carbon fibre against a titanium body.

Thirteen Model Years, One Dyno Run

This part covers the K 1600 from 2011 to 2024, and BMW revised the bike twice in that span: new bodywork and electronics in 2017, then Euro 5 compliance and a new dashboard in 2022. The six-cylinder engine and the exhaust mounting carried through all of it, which is why one silencer serves the whole run.

The figures published here were measured on a 2011 K 1600 GT/GTL, the first year. They describe what the system does to that engine; on a 2022 machine the fit is the same and the numbers should be read as the family's behaviour rather than a certificate for your specific year. The GT and the GTL differ above the frame — screen, seat, top box — not below it.

Fitment and Compatibility

S-B16SO4-HZAAT covers the BMW K 1600 GT, the K 1600 GTL and the GTL Exclusive from model year 2011 through 2024 — fourteen model years on one part number. The BMW side case system mounts over it unchanged, which on this machine is not negotiable for most owners.

The 2025 and later K 1600 GT uses a different system, part number S-B16SO5-HZAAT.

Road Approval

EC type approval and ECE type approval, with the certificates supplied and downloadable from this page. The silencer is a legal replacement part for road use in the European Union with no entry required in the vehicle documents.

Specifications

• Part number: S-B16SO4-HZAAT
• EAN: 3831126403096
• Fitment: BMW K 1600 GT, GTL, GTL Exclusive (2011–2024)
• System type: slip-on silencer
• Material: titanium
• Outlet caps: carbon fibre
• System weight: 8.4 kg (stock 11.7 kg, saving 3.3 kg / 28.2 %)
• Power: 144.0 PS at 6,900 rpm (stock 142.4 PS at 6,800 rpm, gain 2.3 PS / 1.7 kW at 5,870 rpm)
• Torque: 161.4 Nm (stock 159.9 Nm at 5,260 rpm, gain 2.7 Nm at 5,600 rpm)
• Noise insert: included
• Side case compatible: yes
• Road approval: EC type approval and ECE type approval
• Country of manufacture: Slovenia