CACC Rule Change Proposal
RCP-2023-1201

18.4.1 Improved Production will be divided into four classes as follows:
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IP1 - Vehicles with engine displacement of 2751 cc and up

18.4.1 Improved Production will be divided into four classes as follows:
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IP1 - Vehicles with engine displacement of 2751 cc and up. Also, any "Spec E46" or "Spec Corvette" as defined by their respective rule sets.

As the IP rules currently stand, the permitted modifications are mostly established by the SCCA's (very out-of-date) "Improved Touring" rules. Those rules exclude two growing spec classes. Spec E46 and Spec Corvette are both based around unmodified stock engines, but the SCCA Improved Touring rules make them both illegal for IP1.

Some examples: Spec E46 and Spec Corvette both allow an aftermarket flywheel, but the SCCA/IP1 rules require that a car retain the original flywheel at the original weight. Chassis reinforcement (almost universally required on E46s) is not allowed under the SCCA/IP1 rules. Cut-out hood vents (mandatory in Spec Corvette) are not allowed under the SCCA/IP1 rules.

Both sets of spec rules are overall more restrictive than the SCCA/IP1 rules (e.g. the spec classes require the use of stock engines/transmission/differential), but there are minor things that make the spec cars potentially illegal under the SCCA/IP1 rules. It makes sense to put these spec cars in IP1 - similar to the way the CACC rules put Spec Miatas in IP3 and Pro-3 cars in IP2.