SPT PARTS FOR THE 2008 IMPREZA WRX

Toshiki Kanamori, Yoshikazu Watanabe, and Garrick Goh tested the SPT Power Pack at AEM in Los Angeles.

SPT BEGAN DEVELOPING PERFORMANCE INTAKE AND EXHAUST COMPONENTS FOR THE 2008 SUBARU IMPREZA WRX 5-DOOR AS SOON AS PROTOTYPE VEHICLES WERE AVAILABLE.*

INTRODUCTIONS IN STAGES

Last May, Drive Performance got a behind-the-scenes look at testing some of these new SPT Parts. Subaru of America, Inc. (SOA) and Fuji Heavy Industries Ltd. (FHI) product development personnel met at Advanced Engine Management, Inc. (AEM), in Los Angeles to test SPT Power Pack prototypes. Development personnel included Toshiki Kanamori (General Manager, Accessory Development & Sourcing for SOA), Yoshikazu Watanabe (Assistant Manager, Overseas Accessories Planning & Development for FHI), and Garrick Goh (Performance Parts Project Engineering Manager for SOA).

EXPECTATIONS

The meeting began with Yoshikazu Watanabe delineating the process for testing the parts – first in California, then in Japan. They started with airflow, dynamometer, and sound testing of both the stock and AEM prototype components.

The testing itinerary included measuring the differences in the parts relative to such things as general engine mapping, boost, emissions, and idle at various engine speeds. To do so, four different configurations of intake and exhaust systems were installed in the WRX. Component configurations included:

• Stock intake and exhaust systems
• Prototype intake and stock exhaust systems
• Stock intake and prototype exhaust systems
• Prototype intake and exhaust systems

The tests took place in three locations. Airflow tests through stock and prototype SPT parts were handled in house at AEM. Dyno testing of the four configurations took place at Church Automotive Testing in Wilmington, California. Sound testing happened at a nearby airport.

TEST SUBJECT

The test subject was a hand-built, prototype 2008 Impreza WRX 5-Door. An early build of that model, it was continuously brought closer to what the final manufactured product would be. It did not have a production engine control unit or wastegate actuator hose, so Mr. Watanabe brought these production parts with him from Japan to be installed prior to testing to help ensure test accuracy.

In addition, the WRX wore a number of 2008 accessories, including a mesh grille, rear bumper protector, and boost gauge.

Original equipment and prototype exhaust systems were tested for airflow capacity.

MEASUREMENTS

The team tested to confirm that the parts would add to the power developed by the WRX engine while still falling within emissions and sound regulations. The team charted Yoshikazu Watanabe’s required measurements at specific engine speeds.

Testing to determine if the prototypes provided increased airflow entailed mounting all original equipment (OE) and prototype intake and exhaust components on an airflow measuring device and recording capacity. That and some work with the production engine control unit took the better part of an afternoon. Each system had to be rigged separately to the airflow machine, often requiring parts to be removed from the prototype 5-Door.

At the airport, the team measured decibel levels from the car fitted with the prototype Power Pack. From 15 meters, microphones measured sound emitted at wide-open throttle while accelerating in second and third gears. Multiple passes were made by the car fitted with the different combinations of components. Also, the noise level measured directly behind the car while it was revving ensured that it was below 93 decibels. The exhaust system with the right Boxer engine sound passed the tests within set limits.

Testing on the Church Automotive Testing dynamometer proved that the prototype intake and exhaust systems added horsepower and torque over the OE components. The dyno also measured emissions, boost, and other parameters. In addition to pulls to red line, the dyno provided measurements while holding constant a number of specific engine speeds.

One test result was the modification of the pipe's cross section where the mass airflow sensor in the intake system. It was changed to allow measurements for safe air/fuel ratios otherwise the mixtures would have been excessively lean.

CONFIRMATION

The team was satisfied with prototype parts performance and the exhaust sound (an enhanced Subaru Boxer rumble). However, the results had to be confirmed by even more testing by FHI in Japan. The same battery of tests was run, plus others, including water ingestion tests.

SOA and FHI don’t just choose an aftermarket company’s components and put SPT logos on them. The companies expend considerable resources to ensure that SPT parts pass certification regulations in all states, fit properly, and function as they’re intended. Extensive testing also ensures long-term reliability, enabling Subaru to cover them under factory warranty.