Catalysts and decat pipes

This section brings together two parts that fit in the same stretch of the exhaust and do exactly opposite jobs. A MIVV motorcycle catalyst is the accessory some of the brand's exhausts need to stay road legal; a decat pipe, also called a cat delete, removes the catalyst and is strictly a track part. Before you look at part numbers, ask yourself one question: will the bike be ridden on public roads?

Same slot, opposite purposes

Catalyst: what makes an approved exhaust complete

Several MIVV exhausts for Euro 5 bikes only meet their type approval with a metal catalyst from the brand itself, housed inside the silencer. It is bought as a separate part, and the exhaust's product page tells you whether it needs one and which, with a code such as ACC.046.A1. Fitted without it, the silencer is no longer the approved version, even with the E-mark stamped on it. The codes and the exhausts they go with are listed under MIVV catalysts.

Decat pipe: a straight tube for the track

A decat pipe replaces the section that holds the original catalyst with a plain tube. Riders fit one for track days and racing because it saves weight and opens up the sound, but it takes the bike outside its emissions approval: it is not legal on the road and will not pass an MOT or any other roadworthiness test. MIVV and IXIL make them for specific models, from the Duke 390 or Ninja 400 to the Ténéré 700, the Hayabusa or the Voge DS800 Rally and 900 DSX. Each brand's range has its own page: IXIL decat pipes and MIVV decat pipes.

Working out which one you need

1. If the bike is used on public roads, its catalyst stays where it is. The only thing in this section for you is the catalyst your MIVV exhaust calls for.
2. Pick the silencer first, then look up the matching catalyst on its product page. One code can serve exhausts for several bikes and lines, so compare the full code, suffix included.
3. If the bike only goes on track, search for the decat pipe by make, model and year. Some part numbers span two generations, such as the one for the Ninja 1000 SX and 1100 SX.
4. Keep the original part: it has to go back on if the bike ever returns to the road.

Common questions

Can I just hollow out the catalyst?

Gutting it has the same consequences as removing it: the bike no longer meets the approval it was registered with, it fails the roadworthiness test and riding it like that can lead to fines. If what you want is a different sound on the road, the answer is an approved silencer for your version; our motorcycle exhausts page explains how to choose one.

What if the original catalyst is damaged?

A blocked or broken catalyst should be checked at a workshop and replaced with an equivalent one: neither gutting it nor fitting a decat pipe is a repair. Bear in mind that the catalysts here are not replacements for your bike's original unit, but accessories for specific MIVV exhausts.

Does the ECU need remapping?

With a decat pipe, often yes: without the catalyst, exhaust back pressure and the sensor readings change, and a new fuel map is often needed. With a MIVV catalyst fitted in its approved exhaust, you would not normally need to touch the electronics; even so, some product pages rule out Euro 5+ bikes that monitor the catalyst with a sensor placed behind it. If in doubt, ask us on the chat before you order.