509 whp STI

509 whp STI

509 whp STI

April 1, 2019

Fine Line Imports built this 2005 STI for one reason, maximum engine horsepower and torque. With 29 max psi tapering to 24 psi, 509 hp and 478 tq. on 100 Octane fuel mixed with methanol injection was obtained and on 21 psi tapering to 19 psi, 391 hp and 399 tq. on California 91 octane fuel was achieved. The temperature in the Dyno room was 62 degrees with around 45% humidity on the 91 Octane fuel run and 60 degrees with 50% humidity on the 100 octane fuel/methanol injection mix run.

Turbo Power

The engine build consist of a Cobb Tuning Original Series closed deck block with coated forged pistons, Cobb Tunings long forged rods, stock crank and Cobb Tuning rod and main bearings. This block was bolted to the stock STI heads using ARP head studs. With a final compression ratio of 8.2:1, this engine turned out a great fit for California streets with our fuel quality.

The engine set up was based around a rotated mount Garrett GT35 R turbo with a .82 wheel trim. FLI used a Perrin rotated mount up and downpipe which was made from polished stainless steel. This massive turbo was feed air through a custom 3 inch cold air intake which was custom built by FLI. To cool the forced air an APS 725 front mount intercooler was installed. The measurements of this gigantic front mount intercooler is 28 inches wide, 4.5 inches thick and 9.5 inches tall.

For the fuel supply, FLI choose to use APS WRX fuel rails and Power Enterprise WRX side feed 800 cc injectors. This is because at the time APS did not have the STI fuel rails available. A single Walbro 255 ml/per hour fuel pump feed these injectors and was regulated by the factory fuel pressure regulator.

The factory STI 6 speed transmission is a very solid platform so there is no need to upgrade it. However, with all this power to hold the factory clutch will not be sufficient enough. FLI choose the Exedy twin disc clutch/chromolly flywheel kit which does the job very well. A Cobb Tuning ride height and throw adjustable short shifter with erathane bushings was also installed for better shifting.

Here is a an example of what a stock STI performance looks like on dyno.

91 octane graph

100 octane graph

Overall this was a very smooth tune on both maps. 300 tq. to the wheels was reached at 3850 rpm on the 91 Octane street map and 400 tq. to the wheels was reached at 4150 rpm on the 100 Octane/Methanol race map.

Fine Line Imports