The engine ECU uses MAF voltage and the dimensions of the tube in which the MAF is positioned to calculate the amount of air entering the engine. Changing the intake’s shape or cross-section can lead to excessively rich or lean conditions. (Running rich causes damage to the emissions control system as well as the environment. Running lean can quickly ruin the engine itself.)
* The Power Pack consists of the SPT Performance Exhaust System, SPT High Flow Intake System,
and SPT Heat Shield.
† As measured at the wheel.
Rich or lean conditions are measured by a wideband oxygen sensor, and the output can be converted to an air-to-fuel ratio (AFR). SPT engineers measured the AFR under normal and race conditions on the track and on the dynamometer and found that the SPT air intakes do not negatively affect the AFR.
SPT air intakes were subjected to the usual array of stringent environmental tests required by Subaru of America, Inc. These tests include hundreds of hours of continuous salt spray, temperature cycling, and soaking in various toxic chemicals. Against these conditions, the air intakes proved themselves ready to provide many satisfying years of service.
Once SPT engineers were satisfied with the performance of the air intakes, they were submitted to the California Air Resource Board (CARB) to be certified for sale in California, which has the toughest emissions regulations in the country. CARB testing results showed emissions from 60 to 99 percent below the legal limit!
Carefully designed and proven through numerous tests, SPT High Flow Air Intakes and exhaust systems qualify for the SPT badge. These parts not only provided improved performance, but do so without impacting the Subaru reputation for drivability, longevity, and reliability.
More about SPT parts can be found at Subaru Performance Tuning™ Modifies the 2008 WRX®; also see other Upgrades articles here.