93 octane baseline, 93 octane tuned, 100 octane. Most of these gains at higher load were created with a combination of lambda and ignition timing changes. Lower RPM changes were accomplished with exhaust valve and cam timing changes.
91 octane baseline compared to 91 octane tuned. These cars are designed for 93 octane and do not like being on 91 octane. The excessive knock experienced on 91 octane was reduced in the tune with changes as done in 93 and 100 octane but opposite ignition timing changes. 91 octane tuned makes slightly more than a stock car on 93
The 991.2 GT3 is a 4.0 liter car. The stock 991.2 GT3 is extremely impressive. This car makes as much power and more torque stock than does the 3.8 liter 991.1 GT3. The gains on this car above its 93 octane baseline are impressive. The low end torque gain was accomplished with cam timing, fuel control, and exhaust valve timing, Upper RPM increases were accomplished with lambda changes as well as ignition timing and further cam timing (intake and exhaust) timing changes. Large gains were accomplished on 93 octane. Smaller gains were accomplished on 100 octane.
Responded well to calibration refinement on 91 octane fuels. However, as with the 991.1, these tuning changes were not of large magnitude but simply allowed the car to run on 91 without knocking excessively. These marginal gains at higher RPM were in contrast to the large gains at lower RPM. Using similar approach as with 93 we preserved the huge torque gains at lower RPM. This makes the car a lot more drivable – even on 91.
991.1 GT3 RS
The 991.1 GT3 RS was the oddball of this group. Its an earlier car with the 991.1 series but was the first evolutionary move toward the 4.0 liter motor. With a smaller intake and exhaust cam, and a lower rev limit, this car made a little less in overall power gains, and made nearly the same with both 93 and 100.
991.2 GT3 RS
The 991.2 GT3 RS is supposed to make more power stock that the 991.2 GT3. Our test car actually made a little less everywhere. Furthermore, we were confused to see that the GTR3 and the GT3 RS calibrations are IDENTICAL. That said, the only way this car might make more power is through some additional intake charge via the large side scoops. As you might predict, the, the GT3 RS, used exactly the same calibration changes as our test 991.2 GT3. After all, they are the same engine and exactly the same ECU control.