MIVV Catalysts

MIVV catalysts are the part that turns many MIVV exhausts into a road-legal version. On Euro 5 bikes, a share of the brand's silencers and full systems only meet their type approval with their catalyst fitted, which MIVV sells separately as an accessory and identifies with its own code, such as ACC.077.A1.

What the catalyst does and why it is sold separately

A catalyst converts the engine's most polluting gases (carbon monoxide, hydrocarbons and nitrogen oxides) into less harmful ones before they leave the exhaust outlet. MIVV uses metal catalysts, with a metal substrate inside instead of a ceramic one, housed within the exhaust at the point each part number provides for. MIVV treats them as a removable, optional part: they do not come with the exhaust, and anyone riding on public roads needs to add one.

When you need one

• When the product page of your MIVV exhaust says Euro 5 approval is only valid with a specific catalyst. The GP Pro for the MT-07, for example, calls for the ACC.046.A1; the SR-1 for the YZF-R7, the ACC.077.A1; and the STR-1 for the KTM 690, the ACC.041.A1.
• When the bike faces a roadworthiness test: with the silencer fitted without its catalyst, the exhaust no longer matches the approved version.
• When you want the new exhaust to keep the exhaust gas treatment your bike had from the factory.

Check electronic compatibility as well: several product pages warn that the set-up does not suit Euro 5+ bikes with the lambda sensor after the catalyst.

One code for several bikes

Each catalyst serves a family of exhausts, not just one. The ACC.077.A1 appears in GP Pro, SR-1, Oval, Delta Race, HR-1 and X-M1 part numbers for bikes such as the Ninja 650, Tracer 900, GSX-8S or SYM ADX TG 400; the ACC.042.A1 in exhausts for the MT-07, Tracer 7 or XSR 900; and the ACC.099.A1 in the AK-1 for the 2024-2025 MT-09. Others are for a single bike, such as the ACC.037.A2 for the XT 660 Z or the ACC.038.A2 for the Pegaso Strada 650. The A1, A2 and C2 endings are different variants, so compare the full code. The sensible order is to choose the exhaust first and then look up on its page which catalyst it takes.

What a catalyst is not

Do not confuse this category with MIVV decat pipes: they do the opposite, swapping the catalyst for a straight pipe, and are for track use only. A bike ridden on the road without its catalyst falls outside its type approval. Every exhaust line from the brand is under MIVV, and the general side of road approval is covered in our motorcycle exhausts guide.