2013 Cadillac CTS-V

Reading the result

Twenty-nine horsepower and thirteen pound-feet. Those two numbers moving by such different amounts is the whole story of tuning a supercharged engine on California pump gasoline, and it is worth understanding before you spend money expecting otherwise.

Peak torque on an LSA arrives in the middle of the range, where cylinder pressure is highest and the engine is closest to detonating. That is precisely where 91 octane runs out. The calibration cannot ask for much more there without risking the engine, so the torque figure barely moves — and a tuner who makes it move a lot on this fuel is either running a correction factor you cannot see or handing you a problem that surfaces later.

Higher in the range, cylinder pressure falls and knock margin opens back up. That is where the timing can go in, where the intake and the exhaust changes are actually doing something, and where the twenty-nine horsepower came from.

The honest summary: on 91 octane, a blown 6.2 is limited by fuel, not by airflow. Every further gain on this platform costs either octane — race fuel or E85, with a fuel system to match — or boost, with the supporting parts that implies. Anyone quoting you a large number on pump gas for bolt-ons is quoting a different measurement, not a different tune.