In order to keep the IAM up, we decided to reduce timing in that area on the PREracing tune so the ECU doesn’t see any knock and therefore doesn’t drop the IAM down. This area almost always knocks the IAM down on the COBB map if it hadn’t already dropped. The reason for this is that while the ECU is seeing knock and actively pulling timing during this area however the total timing is still higher than our tune. The COBB map makes more power above 6000rpm than the PREracing map. When you look at the overlay of the PREracing custom map and the COBB S1 map you will notice one thing. It seems these direct injection cars are especially prone to knock at part throttle, more on that later. After a couple of full-throttle pulls the IAM climbed up to 0.680 where it wanted to stay. On an interesting note, while the ignition advance multiplier (cars adaptive timing) defaults to 1.0 in the Stage 1 map, it quickly dropped to 0.500 while driving indicating over advanced timing. All-in-all the car is actually easier and significantly more fun to drive. The throttle feels much more linear and less bottom-loaded than the stock tune. Power comes on smooth and pulls hard to about 5500rpm. Driving the car on the COBB Stage 1 map is much more exciting and predictable than the stock tune. Additionally, the boost was much more stable which translates into a smoother power and torque curve. Horsepower on the COBB OTS Stage 1 map was 223.0 whp and 249 ft-lb, a healthy gain over the stock rating. 3rd pull and the IAM climbed back up a little. Another pull and the IAM stayed the same. Immediately the IAM (dynamic advance multiplier) dropped down below 1 which is an indication of timing and knock issues. After letting it run for a bit and running it through some gears on the dyno to allow the ECU to learn we did the first pull. To get the party started we loaded the off-the-shelf (OTS) 91 octane stage 1 map onto the ECU. The WRX has absolutely no electrical or mechanical modification for stock tests and only a COBB Accessport tuner for tuned tests. Quick references: Actual vehicle weight 3,307 lb.

This boost inconsistency was present on all pulls done with the stock tune. The boost came in spiking to nearly 20psi on the dyno, then back down to xx psi then back up before finally tapering off towards redline. The thing that was the most shocking was the boost curve, or rollercoaster rather. This yielded slightly higher numbers on the first pull but on subsequent pulls we were back down to the previous numbers. We decided to reset the ECU as often Subaru likes to learn lower timing. A little shy of what we had expected from drivetrain loss over the advertised 268 horsepower. On the stock tune, the vehicle put down 197.7 whp and 228 ft-lb tq. After that, it was off to the dyno for initial testing. To baseline our new 2015 Subaru WRX we decided first to put around 1000 miles on the chassis to break it in.

It’s always a good idea to get a baseline when modifying anything so you know that your modifications are working as intended.

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