A forgotten part of the 964s history is the Turbo S2, and is started in 1991. Only 20 1992 964 Turbo S2 road cars were built by Andial for Porsche North America, making it one of the rarest 964s built.
In 1991, the International Motor Sports Association (IMSA) introduced the Bridgestone Supercar Championship as a support race during the GT series, which grew to attracting both amateur and pro drivers to the series. The cars raced in the series were essentially the top end cars offered to the public at dealers. Homologation regulation requirements were that manufacturers had to deliver a minimum of 200 road going cars to the U.S. market, which also had to include 20 ‘race versions’ as well.
In 1992 Porsche wanted to compete in this IMSA sports car series but needed to produce a required number of road cars to meet those homologation requirements. While the initial racecars were developed in Germany then sent to the U.S. for race preparations, the S2 Turbo was actually exported to Andial as fully optioned 964 Turbo models.
This would allow Porsche to export the 20 cars without having to make any drastic changes to meet EPA and DOT regulations. With that constraint taken care of, Andial would then option the cars with the homologated “power kit”, and send them off to chosen dealerships for sale with a $10,000 price tag markup. 18 ended up in U.S. showroom floors, and 2 ended up in Canada.
It was typical Porsche. Testing the outer limit of the rules, building a truly great car for racing, just to adhere to homologation rules so Porsche could participate in IMSA’s sports car racing series. Rules were met and Porsche “built” at least 200 road-going versions of the participating car, 20 of which shared enough of the primary components of the race car to successfully get approved to go racing. The 911 Turbo S2 was built specifically for this purpose and exclusively for the United States and Canada.
The 20 homologation specials left the factory as stock 964 Turbos, heading immediately to California-based tuner for “S2” engine upgrades. So what were those upgrades?
These road-going “race versions” of the 964 Turbo received an upgraded K27 turbocharger, a larger intercooler, upgraded cams, as well as ported and polished heads among a few other supporting modifications. This homologation power package fitted by Andial boosted power to 322 bhp @ 5750 rpm (although many people say the true number was quite a bit higher, likely in the 380-400bhp range).
Porsche’s efforts proved a success for them with the 911 Turbo taking home numerous pole positions in the IMSA Bridgestone Supercar Championship, throughout 1992 and 1993, with household-name drivers behind the wheel including Hurley Haywood and Hans Stuck.