Update exhaust rules
#37955 from B-Spec/C-Spec Committee · Recommended to the Board · Minutes (2025-05 Fastrack)
In GCR, Section 9.1.10.E.25., change as follows:
"(Effective 6/1/25) 25. Only OE catalyst are permitted. The exhaust system downstream of the primary catalyst may be replacedprovided:A. Said replacement system retains the same original configuration, e.g., routing, single, dual, etc.B. The system exits from the body in the same approximate location(s) as the original. When an original equipment singleexhaust system is cosmetically split into dual outlets, it is permitted to continue as a single system provided it exits inapproximately the same location as one of the originals.C. The system meets all appropriate event-specific sound level requirements.
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D. All oxygen sensors must be intact and in stock location.E. Primary catalytic converter may not be modified in any way.F . The Mazda 2, Fiat 500, 2007-10 Mini Cooper all may remove the primary cat/exhaust manifold to install their approvedheader. All oxygen sensors must be maintained. The original heat shields or heat wrap may be used to insulate the replacementheader from objects they come close to.
25. OEM primary/upstream catalysts are required unless a vehicle's spec line has an approved header listed or is specifically
permitted to remove the catalyst. The primary/upstream oxygen sensor must be installed and functional. Secondary oxygen
sensors may be removed. The exhaust system downstream of the primary catalyst/approved header may be replaced provided
the system retains the original routing and exits the body in the approximate location(s) as the OEM system. Single exhaust
systems that are cosmetically split into dual outlets may use a single outlet. OEM heat shields and/or exhaust heat wrap may be
used."