I'm thinking18g is better over all quick spool and better top end. 04 wrx Sti is what I have. Any input about the turbos or you personal experience would help about the two. Thanks

 

yea if you got to choose over 18g or vf39... for sure the 18g. I think your sti comes with a vf39 tho. anyway.. the vf39 is notorious for it's hair line crack on the housing.

I've owned the vf39 first and then i cracked it, i lost pressure so i siwtched over to a vf34.

 

I lost pressure aswell. And oil in my intercooler alittle smoke to. So its time for a upgrade.

 

for an sti id do nothing less then a 20g

 

This^^

From what I've experience and seen. A vf39 will yield u insane Tq numbers where as the 18g will give you the higher HP number. Coming from both turbos I would have gone bigger ie 20g or a green or something along those specs. 18g is a waste IMO on a ej257.

 

20g on the sti! It is not that much more expensive and will suit the sti better. Forced Performance is also having a great sale on the FP red right now (down to 699) but it will be probably bigger than you need.

 

Just remember, with a bigger turbo comes the $$$ associated it... supporting mods...just some prices I've seen used/new off the top of my head...you could plan and save yourself a lot of money by buying good, used equipment.

Assuming you already have: Up/Downpipe/Catback/Intake like most people.

Minimally:
Fuel Pump ($150)
Injectors ($400-$600) used/new
Bigger topmount or front mount intercooler ($400-$1300)

Other mods that will help make power and decrease spool time...
Electronic Boost Controller ($150)
EL/UEL Header ($200-$1200)

And don't forget...
Tune ($420-$600)

Of course, you could go all out...but the above lists the most common upgrades people do with a bigger turbo...

Comes down to what you want to do and how deep your pockets are.
I was totally happy with my FP 18g on my 04 STI...no lag to speak of and great 0-60 acceleration...it was a lot of fun. On the other hand, I saw Chasen recently make 371hp/37xtq with a TD06h-20G (06 STI) at the latest PDX Tune Day with Jarrad...crazy numbers! He had all the supporting mods and 50/50 Meth...but still...awesome.

Just wanted to chime in to show you what you could be getting into with a bigger turbo...modding is an addiction...once you start, it's hard to stop...

 

i had a 18g on my old car and it was great

 

Yes i made 371whp/376wtq with my 20g, spool is amazing, almost like my stock turbo stg 2+ setup. without meth you could still make a good amount of power. Considering how conservative you want to be and what kind of supporting mods you invest in. Id say the 20g was well worth it for me.

 

I have an 18g on my STi. Spool is quick-ish, but it falls flat on it's face in the top end, kinda how the vf39 does. Good enough for autox though (which is what I had it tuned for)