Not legal 1 class
Superchargers are banned outright in this turbo class, so no supercharger or supercharger part may be fitted. · DD.7
IHRA · Forced induction
Aftermarket supercharger, IHRA
IHRA answers this part for 24 of its classes. 3 of those answers permit the part outright and 3 permit it with stated conditions, leaving 18 that do not. 2 of the ones that do not are classes we read as open rather than as refusing it. 10 are inferred from how the class is written rather than quoted from a rule naming this part.
Where it stands, class by class
24 classes, grouped where the same rule gives the same answer rather than listed one by one, because an answer that holds for a class usually holds for every class that borrows its rules.
What each answer below means
- Not legal
- This comes off. The rules refuse it in this class.
- OEM part required
- This comes off. Only the part the manufacturer fitted is allowed here.
- Not permitted, not listed in the rules
- Treat it as coming off. The class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list, so this is our reading rather than a rule we can quote at you.
- Legal, with conditions
- Keep it, but measure it: the rules permit this part only inside stated limits.
- Legal
- Keep it. The rules permit this part in this class.
- No rule, this is an open class
- Probably keep it. The class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms, and this is our reading rather than a permission anybody wrote down.
OEM part required 1 class
Must remain OEM stock, and no aftermarket unit is listed. The supercharger clutch may be aftermarket if readily available to all competitors from a reputable manufacturer; on the Kawasaki Ultra 300/310 pulleys and tensioners may be modified or aftermarket, and on Yamaha SVHO models the supercharger shafts may be welded. · W.1, W.3.6
OEM part required 1 class
No aftermarket unit is listed, so the supercharger the craft came with stays. Its components may be reinforced for safety and replacement parts are allowed, with the original gear ratios kept. · J.1, Y.6.1
OEM part required 1 class
No aftermarket unit is listed. Z.1 admits four-stroke engines only as naturally aspirated, while Z.9.1 lets supercharger components be reinforced for safety and allows replacement parts with the original gear ratios kept; neither withdraws the other. · J.1, Z.1, Z.9.1
OEM part required 1 class
No aftermarket supercharger is listed in DD.1, so the unit stays the one the craft came with: its impeller OEM and unmodified, its gearing OEM with no re-gearing, and no older centre gears on Yamaha models to change the OEM ratios. Within that unit DD.1 allows aftermarket shafts and rebuild kits, and lets front and rear housings be OEM or aftermarket to OEM specification before saying in the same bullet that housings must remain OEM and unmodified. DD.1, DD
- Drag, Yamaha Pro Stock · DD.1
OEM part required 1 class
DD.2 opens only aftermarket supercharger wheels and lists no aftermarket unit, so the supercharger the craft came with stays, keeping the OEM-style gear drive off the flywheel at the PTO. Water cooling of the unit is allowed. DD.2, DD
- Drag, Sea-Doo Pro Stock · DD.2
OEM part required 1 class
DD.3 lists no complete aftermarket supercharger, only parts of the one the craft came with: the impeller may be aftermarket, and the front housing OEM or aftermarket to OEM specification with no modification. Gearing stays stock with no re-gearing and no older centre gears on Yamaha models, and aftermarket shafts and rebuild kits are allowed. DD.3, DD
- Drag, Yamaha Spec · DD.3
OEM part required 1 class
BB.6.1 keeps the impeller housing OEM, so the supercharger itself stays the original unit. Its internals, pulleys, tensioners and intercoolers may be aftermarket or modified and a spacer may fit a larger impeller, which makes it a modified OEM supercharger, not an aftermarket one. · J.1, BB.6.1
Not permitted, not listed in the rules 8 classes
On a closed list an unlisted modification is not permitted. · A.2.2, J.1
Legal, with conditions 1 class
Must retain the OEM-style gear drive off the flywheel at the PTO. · DD.4
Legal, with conditions 1 class
Engines 1100cc or less only. · K.5.1
Legal, with conditions 1 class
Four-stroke entries: Limits: max displacement 1100 cc. · V.6.1
Legal 1 class
Aftermarket superchargers are permitted, and DD.5 sets none of the gear drive or impeller limits of the Pro Stock and Spec classes. · DD.5
Legal 1 class
Power adders are allowed in terms, which takes in an aftermarket supercharger and its internals, in a class that calls itself run what ya brung. · DD.10
Legal 1 class
Aftermarket turbochargers and superchargers may be used or added to a naturally aspirated four-stroke, and the original unit may be modified, provided no hazard is created. · X.4.1
No rule, this is an open class 1 class
No restriction in section CC, and CC.1 permits any modification it does not restrict.
- Freestyle · CC
No rule, this is an open class 1 class
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, Unlimited · DD.6
What we corrected here, and when
- Runabout GP3. Corrected 2026-10-05: the Runabout GP3 aftermarket supercharger row left out the replacement parts that Z.9.1 allows, and now notes that Z.1 admits only naturally aspirated four-strokes.
Aftermarket supercharger: 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 · checks on parts the shop sells · how this site reads a rulebook.
Forced induction · four stroke · legal in 6 of 24 answered, 3 with conditions