Once again, Porsche has left the door open for engine performance improvements with the 981 Boxster Spyder and Cayman GT4, using the same factory intake found on the less-powerful 981 S and GTS models, despite the Spyder/GT4's 3.8L 911 engine. These intakes use the smaller, more restrictive 74mm throttle body which limits power and torque to keep the 981 from treading too close to the 911.
Porsche's 991 Carrera S delivers 420 HP while the GT4 delivers 385 HP with the same engine. Why does the GT4 produce a whopping 35 fewer horses? (The GT4 engine is only 15 HP stronger than the base Carrera 3.4L engine!) How can that be? The Carrera S engine, with its stock 82mm throttle body, benefits from the IPD Plenum, so we figured the GT4 would really perform better with an IPD Competition Plenum and the much more appropriate 82mm throttle body.
Initial dyno tests performed in Germany showed gains of 18 HP and 17 lb-ft of torque at the GT4's wheels. Considering that the 981's ECU requires more adaptation time than other Porsche models (over a hundred miles for the full adaptive process), this means the full performance gains for the GT4 will be even greater.
Competition Motorsport installed the IPD Competition Plenum and 82mm TB in our GT4 and were immediately impressed with the increased mid- and top-end power, throttle response, and mid-range torque. The IPD plenum delivers net gains throughout both power and torque curves, helping the GT4 compete with its GT3 big brother.
** This IPD Plenum requires a Bosch 82mm throttle body (can be added above) **