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
Supercharger internals, clutch and pulleys, IHRA
IHRA answers this part for 24 of its classes. 3 of those answers permit the part outright and 10 permit it with stated conditions, leaving 11 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.
This page is IHRA only, and the bodies do not agree. The same part under IJSBA and UIM. Which one applies to you is decided by whoever sanctions the race you enter.
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.
- 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.
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
Clutch may be aftermarket if readily available to all competitors from a reputable manufacturer. Kawasaki Ultra 300/310: pulleys and tensioners modifiable. Yamaha SVHO: supercharger shafts may be welded. · W.3.6
Legal, with conditions 1 class
Components may be reinforced for safety. Replacement parts allowed but original gear ratios must be maintained. · Y.6.1
Legal, with conditions 1 class
Under Z.9.1 supercharger components may be reinforced for safety and replaced, keeping the original gear ratios, yet Z.1 admits four-stroke engines only as naturally aspirated, so the section contradicts itself. · Z.1, Z.9.1
Legal, with conditions 1 class
Impeller must be OEM and unmodified. Housings OEM or aftermarket meeting OEM spec with no modifications. Gearing and housings OEM and unmodified. No re-gearing. Yamaha may not use older center gears to alter OEM ratios. Aftermarket shafts and rebuild kits permitted. · DD.1
Legal, with conditions 1 class
Aftermarket wheels permitted but the system must retain the OEM-style gear drive off the flywheel at the PTO. Water cooling permitted. · DD.2
Legal, with conditions 1 class
Impeller may be aftermarket. Front housing OEM or aftermarket meeting OEM spec. Gearing must remain stock, no re-gearing, no older center gears. · DD.3
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
Four-stroke entries: IMPELLER HOUSING MUST REMAIN OEM. Internals, pulleys, tensioners, intercoolers may be aftermarket. Spacers allowed for a larger impeller. Oil line fitting may be added to the shaft. · BB.6.1
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: on supercharger internals for Runabout GP3, this row now carries the Z.9.1 allowance for replacement parts and the clash with the naturally aspirated limit in Z.1.
Supercharger internals, clutch and pulleys: 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 13 of 24 answered, 10 with conditions