After 1100 kilometers of driving, the car was finally ready for some dyno testing. Temperatures were quite hot today, and as usual for the Tokyo area of Japan, very humid. Despite that, the car turned out some fairly good numbers on the Dynapack dynometer. After we got all the testing equipment hooked up and running, it was time for the very first baseline run. With the high ambient temperatures factored in, the car ran a smooth 236hp at the crank - right on Subaru of Japan's figures.
Now that that was out of the way, it was time to see what some minor modifications would do. We placed an AVO high-flow panel filter in and gave it a back-to-back run. The figures were even better than we hoped, picking up a good 7hp and between 6 and 10ft/lbs of torque just from the filter alone! This was not just at peak, but across the board from 3500 to 7000rpm. It also removed a little dip in power that happened between 3500 and 4000rpm. Overall a nice gain for little investment, especially as the AVO panel filter will last much longer than the stock unit.
Something interesting that we found out when we pulled the air box apart was that while Subaru did use a version of the Legacy GT airbox, it is not a direct copy. The Impreza airbox does not have a resonator section that protrudes into the fender well like on the Legacy, possibly just because there is not enough space for it.
Another minor update is the feel of the car with the new wheels and Direzza Z1 tyres on. At a +44 offset, I was not sure if the Gram Lights would fit, but they do - barely. It really does help the look of the car, pushing the wheels right out to the edge, giving it a more menacing appearance. The new rubber certainly gives it more traction, and gives me a better idea of the suspension.
Which I still feel is very, very good in design. While it feels even softer now thanks to the increase in grip, it still has great turn-in and hangs on like a leech if you remain committed through the corner. With real rubber on it really begs for a bit stiffer stabilizer bars along with a bit more manly springs. Things to do, things to do.
