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Subaru WRX TGVs for Power and Profit

Start with the wrong parts and you'll have the wrong fun

So where were we? Alright, skipping the speeches about planning ahead, researching applications and not jumping the gun, we'd pulled a hip-shot, buying un-researched speed parts without a plan to execute.

Nice Parts, Wrong Job

It was tasty stuff—Version 8 Subaru WRX STi manifold combination, including the red-head manifold, tumble-generator valves, injectors, fuel rails, wiring harness, throttle body and a mountain of fasteners. The thing had come off a junked 2005 STi, which looked like it had fallen off a cliff. In the effort to part out the car and get to the engine before the owner realized what it was worth, the manifold and associated bits came with, $150 for the combo.

The parts separated were probably worth $2000 retail. They were used, and some metal fragments from piston-to-valve contact had fouled one of the TGV ports (nothing we couldn't clean up), so knock some of the ceiling off that value (not too much, these are relatively rare hi-po bits). The price was still right. We were in it for the red-head manifold (an STi-only bit) and the TGVs. Neither were the right ones, but we didn't know it.

Outfitting a Version 7 WRX with the V.8 parts isn't a problem for the nuts and bolts, but the electronics and software weren't going to get along. The 2005 STi motor uses a host of parts absent from the 2002 WRX, primarily the electronic throttle body, so the throttle body couldn't work. No problem—we had another 2002 unit we'd planned to port and knife-edge. The 2005 STi manifold was manufactured to match the 2005 STi throttle body and didn't have the idle port necessary for a cable-driven unit, so it couldn't be adapted short of massive cutting and epoxy work. Forget that. It sold to someone with a WRX STi who wanted to port a backup instead of the original, just like the throttle body. The two of them sold for about $300 and doubled our outlay. So much for regret, but now we needed to locate the right bits.

We thought we had hit gold with the TGVs. A nasty obstruction in the primary intake runners, they were a concession by Subaru to help the car pass cold-idle emissions that inevitably harm power production. You can remove the butterflies within them and grind out the partition and, not only can the car still pass smog, it's worth 20-plus ponies. Unfortunately, the TGVs house the injectors (until 2006), and the STi injectors were different from the WRX injectors (top-feed instead of side-feed on the STi), and wouldn't fit. The injector boss was a different size and, short of reprogramming the CPU, the STi injectors were not going to work. Hindsight being what it is, we had the STi injectors and fuel rails and could have sprung for the programming when all was bolted together, but avoiding reprogramming was part of the initial poor man's plan.

Making the TGVs Less Worse

This is where doing some investigation prior to the purchase would have been a bright idea. The price of the pile of parts had already come up roses (the STi injectors would sell for another $100), but the one flower we wanted to pick wasn't going to work without a CPU reflash. Too bad we'd already started in on the port job with the TGVs—we didn't recognize the alternative injector receivers until the port partition was gone, the butterflaps dodo and the butterflap ledge smoothed. Nuts. All that was left was to clean the whole port up and they were finished. So we finished. We made a trip to Beto Campa's shop (maximumpowertechnologies.com) for the final smoothing. His full-size porting equipment made the big reach into the TGV easy to handle, especially compared to working with the shorty bits of the Dremel that had served us so far.

At this point we had a sweet set of ported STi tumble-generator valves that were worth their weight in used tar for our WRX due to an absence of planning and the subsequent incompatible injector bosses. For the first official porting project ever to cross the bench in our new Fletcher Hills facility (the garage), it was a successful gig. As for our original intent to install these on our 2002 WRX, well, humbug. We traded the TGVs to a friend who had a STi aftercooler in his garage (having converted his STi to front-mount months earlier). Anyone got a set of WRX TGVs? This time we think we know we need 'em.