I basically have an sti wagon (Forester XT with lots of crap on it) I have a VF39 now and an ecutek reflash. I am getting lots of boost creep (20.5lbs worth) and know that it is common with IHI and aftermarket exhausts. I am planning to port the vf39 but starting to think that I might just order a new one or say a 34. If I decide to run the vf34, will I need to change my injectors/pump? I basically have sti (stock usdm 04) injectors already. I have to send my ecu back out anyway for some tweaking so I can get that part of it addressed. Just curious if anything else needs to be done to have it work right. Has anyone just swaped the 39 for a 34 and experienced any problems with stock em?

BTW, I am actually happy with the HP I am getting right now but want the boost creep to be gone. I figure that I can order the 34 or 39 with a monster port and give that a shot and my power should be the same!

You'll need new injectors and a bigger fuel pump. Stock STi injectors can only support the stock VF-39.

Turbo FAQ (http://forums.nasioc.com/forums/showthread.php?t=555332) lists your options.

Looks like I will just go ahead with my porting and start saving for injectors and a pump. Then worry about another turbo. My only concern with running say a tD06H/20g is my stock tranny. Basically this is the weak link compared to the sti. I am afraid that it will pretty much kill the tranny and cost me another $5k. I think that is why I am rather happy with the power I am getting right now. I mean the car is still a wagon from crying out loud and faster than most cars out on the road already. I think that going to a larger turbo at this point is just because everyone else is. But larger injectors/pump could not hurt at all.

Unabomber:
While you were posting your response I did a search and found this thread. I think I was up to like page 4 before I got out of there.

http://forums.nasioc.com/forums/showthread.php?t=514589&highlight=vf34+swap

None the less, he was running the 34 with stock injectors and pump with no problems. In fact he stated that he was actually running rich on his dyno pulls. To me this does not make sence as the 34 has a larger compresser/exhaust fans in it. I would tend to agree with you but are his numbers correct?

Don't get me wrong, it is cheaper for me to just port the 39 that I already have but if there is a few extra ponies out there and injectors/pump do not need to be changed right away I would certainly consider it.

The differences between the VF30/34/39 are negligible--just port the 39's wastegate.

That is pretty much the plan. I figure if I screw up the port it will then give me a reason to actually buy a larger turbo and what not. Until then I will be fine!

The 34 is essentially the 39 with ball bearings. A little different flow but not enough to make you have to change pump or injectors. You should just send the 39 to Davenow let him muscle it up for a bit and swap it back in. Along with the boost restrictor I sent back to you, they should cure that CREEP issue.

I am putting the car in the garage tonight and plan on starting the tear down later in the evening. I should be able to actually pull the turbo out first thing in the morning and start porting it and have it back in by lunch time! Wish me luck!

Good luck. PM Davenow and ask him for a little porting advice.

I need that link again!

I'll PM you his addy on Forester.com

got it and he pm'd me back. I think I am good. Will check all hoses and install restrictor if it comes today first!

does VF34 spool up a lot faster than VF39? big difference?

Negligible difference @ best.

Got the restrictor in and on the car. Please note that there was one there but it was a modded one. In any case, I took the car out and pulled all they way to red line (pedal to the floor) in 3rd. I have not been able to do this since the cold weather set in and the ecutek went on the car (about the same time actually). I did it again, I got it up to about 5k rpm in 3rd, slowed down and then mashed the gas again. Nothing, it held boost all the way to red line. I was seeing 1.4+bar. Today I saw between 1.2-.3 but I noticed that it would hold it instead of backing off ever so slightly. Note that it is still 34 degrees outside so that might still be playing a factor here. The next trick will be to get it out on the highway and try the same sort of run in 4th or down shift from 5-4 as if I was going to pass someone. That will cause it to spike pretty quick and hopefully we will not see 20lbs of boost. Will see.

So did you not port the wastegate then?