Subiesport Magazine - June/July 2008 - (Page 65)

2007 LEGACY GT PROJECT The Quest for More Power FOR ANY TURBOCHARGED car, there are several ways to make more power. The first method is to open up intake and exhaust passages and use larger diameter piping; this reduces intake and exhaust flow restrictions and allows the engine to operate more efficiently. Another way to increase power is to increase boost pressure, which forces more pressurized air into the engine. When combined, and with proper tuning, these two methods of increasing power can realize serious gains. Yet, there will come a point in your quest for power where bigger pipes will not do and your stock turbo has simply run out of breath. To get more go for your chariot, you will need a larger turbo. That is exactly where we found ourselves with our Project 2007 Legacy GT. While we had a pretty solid setup going, we were still not a part of the 300hp club. This, even though we had a largerthan-stock turbo. The Blauch, TopSpeed 18G, the turbo that we have been running, is a compromise of sorts. It stuffs the guts of a larger turbo into the stock compressor and turbine housings of the VF40 Legacy GT turbo. We were also running a full Perrin turboback exhaust with catalytic converters, Perrin was limited. To be sure, turbo lag is at a minimum with this setup, but it does run out of breath on the top end. The Legacy also presents another challenge. Since the turbo bolts directly into the intercooler and the intake manifold is quite a bit different than that of an STI, bolting in an STI-style turbo is not an option without swapping over an entire STI intake manifold setup, difficult indeed since the two are quite a bit different. However, there are a few companies that make Legacy-specific turbos, like AVO. It should be noted that you can use a STI-style turbo with your stock manifold and a standard Perrin front mount intercooler kit; however, this can be a costly option and larger turbos can spell doom for your engine. See our engine build article in this issue. AVO sells a range of turbos for the Legacy owner wanting more go than the stock snail can provide. The AVO 380 is the baby of the bunch, about the size of a 16G. The AVO 420, the turbo we installed, is a bit bigger, about the size of an 18G. There are a few design elements that make the AVO turbo a very robust unit. First, they are based on Garrett ballbearing turbos. Second, they use slightly oversized Story by Travis Geny Photos by Ryan Douthit These turbos will work with the new 2008 Impreza, too. TMIC, and an ECUTek reflash. This was good for a peak of around 290whp and 300lb/ft of torque. Not bad. The problem is that while the Blauch turbo is a great turbo and makes much more power over a stock unit, it is essentially limited by the housings. In short, we can only cram so much intake air and exhaust gas through the stock housings before they choke off. Normally on a true TD05 18G, peak horsepower levels of 320-340whp can be achieved, but because this was not a true 18G, peak power turbine housings, which reduce wear on the center cartridge but hurts spool somewhat. AVO rates this turbo at 420bhp (flywheel hp). Keep in mind, these hp ratings were achieved on Australian 98 octane wonder gas, not our anemic 92 octane, which is even more anemic if you get it in Washington. The AVO turbo comes with everything you need to install it and fits very well. However, if you have a later Legacy GT with the smog pump, be warned that the turbo oil return tube will have to be SUBIESPORT MAGAZINE 65

Table of Contents Feed for the Digital Edition of Subiesport Magazine - June/July 2008

Subiesport Magazine - June/July 2008 Contents Editor Letters Readers’ Rides Subaru News Fresh Squeezed Hell's Legacy Under the Radar Project GT Rebuild New Engine AVO 420 Turbo Perrin Intercooler Rally Like a Rockstar Rally Jordan Adventure WRC Rally Argentina WRC Rally Jordan WRC Rally d’Italia Sardegna Where to buy Subiesport WRC2008 Debut Rally America: Olympus Ad Directory Rally America: Oregon Trail Spotted!

Subiesport Magazine - June/July 2008

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