OEM part required 1 class
Must remain OEM. Stinger-diameter reducing insert allowed; cooling lines may be added to the insert. · O.2.5
IHRA · Exhaust
Aftermarket expansion chamber / tuned pipe (2-stroke)
The highest-value two-stroke part and the one IHRA splits hardest by class.
Ski Lites and Runabout GP3 two-stroke forbid it outright. Ski Limited permits it on the same machine. Never answer without naming the class.
Where it stands, class by class
14 classes, grouped by the answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules.
No rule, this is an open class Our reading, not a rule we can quote at you. This class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms.
Legal, within limits 1 class
Previously drilled/tapped manifolds usable if sealed. Exhaust flanges may be removed. OEM resonator may be removed. Water box must remain OEM. AFR sensor mounts permitted. External outlet may be relocated or aftermarket. · Y.2.5
Legal, within limits 1 class
Model-dependent. Four-stroke entries: Previously drilled/tapped manifolds if sealed. Flanges may be removed. Z.2.5 Two-stroke entries: Stinger-diameter reducing insert allowed. · Z.3.3
Legal, within limits 1 class
Model-dependent. On the Kawasaki X2 pre-2005, the X2 2005 to 2007 and the Yamaha WaveBlaster 701, WET-STYLE SYSTEMS ONLY, with dry-type systems and water-jacketed chambers prohibited and no tuned portion outside the hull. Electronic water injection is prohibited on all models. On the Sea-Doo HX the stock exhaust and water box must be unmodified, with no spray bars, stinger sprayers or water injectors, factory water routing and no bypass systems, and larger bolts or studs allowed. · U.2.3
Legal, within limits 1 class
2-stroke: reducer may be placed in the stinger; water fitting may be added. 4-stroke (M.4.2): hose between waterbox and outlet modifiable. · M.4.1
Legal, within limits 1 class
Two-stroke entries: Manifold, head pipe, expansion chamber, gaskets, and hose to the OEM water box. Exit location and original opening size must be maintained. · P.2.1
Legal, within limits 1 class
Model-dependent. On four-stroke entries removal of the plastic resonator is permitted (BB.2.6). On two-stroke entries the manifold, head pipe, expansion chamber, gaskets and the hose to the OEM water box may be aftermarket, the exhaust gas location may not be relocated, the original opening size must be kept, THE ORIGINAL WATER BOX IS REQUIRED AND UNMODIFIED, and no tuned portion may sit outside the hull. · BB.3.4
Legal, within limits 1 class
Exit may relocate below the transom bond flange. No tuned components may protrude outside the hull. · T.2.5
Legal, within limits 1 class
Manifold, head pipe, water box, expansion chamber, muffler. Exit may relocate to the transom but must not extend beyond the hull. · S.2.5
Legal, within limits 1 class
No tuned portion may extend outside the hull. · CC.2.2
Legal, within limits 1 class
Four-stroke (V.4.4): no tuned portion may protrude beyond the hull; exit may relocate to the transom below the bond flange. · V.2.5
No rule, this is an open class 3 classes
The class states only what it bans and calls itself run what you brung, against a section DD preamble that says anything unlisted is illegal.
- Drag, 2 Stroke Unlimited · DD.12
- Drag, Stand Up Unlimited · DD.10
- Drag, Unlimited · DD.6
Aftermarket expansion chamber / tuned pipe (2-stroke): if the rule your class applies reads differently to you, or the rulebook has changed since this was read, ask. We answer with the section we read it from, or that we have not read it. Ask a rules question.
Every IHRA class · where the rulebooks differ · signed checks on parts the shop sells.
Exhaust · two stroke · legal outright in 10 of 14