20G. What do you want out of the car? Stock like spool with lots of torque? Sacrifice a little spool time for killer top end?
Depends on what your end goals are with the car and how much you want to spend. Whats your budget? Do you want top end power or response? Will you stick with pump gas or are you willing to go high octane?
So you don't care at all about lag, you just want hp? In that case, bigger is better. Might want to look at a Deadbolt Superzilla 55.
not trying to thread hijack, but i too am very interested in this. i want to push roughly 400whp on pump gas. i'm wanting spool up like the stocker, fast w/ minimal lag. is a 20g what i should go with? what else will i need? injectors, fuel pump, turbo inlet hose, big maf sensor, and possibly a bigger tmic, of fmic is what i'm thinking. i already have em, and tbe. so my question is what turbo, and how much for the tune, parts, and labor roughly?
First you need to choose a dyno. I doubt anything will break 400whp on an STi (pump gas) on a dyno dynamics or mustang dyno. I'll assume you are talking about a dynapak, which is the one I use at SOG. Not much breaks 400whp by a lot on pump gas. I have seen an 8cm green do it but you will probably need something bigger with a 60lb wheel or more to be certain. FP Red, SZ60, SZ65, GT35, etc. should be able to do that for you. I know that slowwrx's GT30R has broken 400whp on pump gas and I have seen some .83 A/R Perrin 30R's do it too. The FP Red (with supporting mods) is probably the cheapest guaranteed way to achieve 400whp. For that kind of power, you will have noticeable lag compared to the stock turbo. But the perception of lag is relative. I liked how my SZ65 responded at the Club Wars autoX and at little Talladega. I really doubt a 20G will break 375whp by much on pump gas. All these turbos will require new fuel pump, injectors and tune. For stock mount turbos (SZ60, SZ65, FP Red, FP Green), if you pick one with a 3 inch inlet, you will need a new inlet tube and will probably have to delete the TGVs. You should also consider a larger intercooler, most probably front mount. On SOG's dyno, my setup broke 400whp at about 20psi on pump gas. We made ~430whp at 22psi on pump gas on the dyno too, but thats not a streetable tune. Most of my parts are: Deadbolt SZ65 turbocharger with the fatboy wheel APS DR525 FMIC APS 70mm CAI APS turbo inlet tube Deatschwerks 740cc injectors Helix catted downpipe Blitz Nur Spec-R catback exhaust Cobb Accessport protuned by Scott Siegel Apexi AVC-R Boost controller TGV deletes Walbro fuel pump You could get on manufacturers websites and price them out. But honestly speaking, you will probably be happier with a 20G if you will stick with pump gas. I went with the SZ65 because I plan to run methanol injection in the fall. We are expecting around 500whp daily driven after meth.
Thanks Milo for the awesome input! jay...I'm with ya on that one...I have not a clue what a TGV is. *shrugs* *edit- nevermind...quoted from baddriver: (Here's a stolen definition from forced air technologies web page ( Ain't Google great?): "TGV's stand for Tumble Generator Valves, or air tumblers for short. This mod is useful for all of the newer Subarus that have TGV’s. These are pretty useless butterfly valves that lower emissions only on cold starts for like 20 seconds and restrict your intake for the remaining 99.99956% of the time you drive your car." The reason I bought these is that I'm looking at buying a stock location turbo that has interference issues with the ancillary hardware that hangs off of the TGV housings.
TGV = Tumbler Generator Valve. TGV deletes remove the TGV out of your intake manifold. The TGV is there for emissions and supposedly low end torque. The TGV is a butterfly valve which opens and closes. I have the TGV deletes on my car, but was having a major problem with CELs. APS now sells TGV deletes with the CEL fix.
This is what the TGV butterflies look like. People say they help increase power, but I haven't seen conclusive evidence backing this claim. I had to take them out for my turbo to fit with the bigger inlet. The next picture compares the SZ65 (my turbo), VF39 (stock STi turbo) and TD04 (stock WRX turbo)
Thanks Brett By the way, I didn't need to buy any TGV deletes. Will plugged the holes with bolts. The TGV codes were simply turned off by protuner.