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Discussion Starter #1
Ok so I searched for a bit and did not find the exact answers I wanted. I am looking for limitations of the VF39.

What PSI is it good to before it starts spinning too fast and becoming inefficient?

What is the horse power limit on the VF39? I know this is vague but lets just say with supporting mods when would the VF39 become the restriction factor?

What RPM does it spool up on the 2.5 block?

I am building a hybrid running a 22T block 8.5:1 compression and RS or WRX heads. I am shooting for 300-350 whp with the minimum amount of lag possible. The VF39 is an attractive option mostly because of how easy they are to get and I have read they are a bit undersized for the 2.5 block. I think it will make a good starting turbo but just wondering what its limit is.
 

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99' Subaru Impreza 2.5 Rs
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well, i can only answer from MY experience. i have a GC8 USDM STI swap. i have stock VF39, with a good amount of bolt ons. if you want to see exactly what i have done, go here!

i dyno'd at 336 hp to the wheels, and 355 lb/ft of tq. At this time, 2 months ago, Dan at tuning factory here in MI, among others siad that they had never seen any stock turbo subaru engine dyno higher than what i did. peak torque was at 3100 appx, so spool is damn good. i run 19 psi on 93 octane. they seemed to think that the VF39 was MAXXED at 336 whp. they could be right, i dont know.

i hope that helps in some way.
 

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Discussion Starter #3
no that is perfect, I just wanted a feel for what the turbo can do. I like torque, and I hate waiting forever for the turbo to spool. I am sure I will have to wait a bit longer on the spool up but you power is right in the range I want mine. How does it feel? pull hard to redline?
 

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i absolutely love it. it pulls hard till about 6500. then the curves starts dropping off significantly. so i shift around then.

i was told that i could push a little more torque out of it, being mroe agressive tune with more PSI, but that would do absolutly nothign for HP, jsut TQ.
 

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The Thread Stopper
11 WRX, Matte black
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I don't know that the VF39 was being maxed at 336 whp. But, without any efficiency maps floating around, we'll never know.

Amorton - the usable range of the 39 is well suited for all our engines. Just for example, here's my EJ205 dynapak plot:

 

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Renegade_ said:
I can see pete (96imprezadent) getting there no problem soon. Don't know what he is at right now though.
i think pete is done with the ej18 block, he is building up a closed deck ej20g block if i remember him telling me correctly..i think right now he is just using a complete ej18 long block with like 7-8 lbs of boost

but, if anyone has hit 300 whp on the ej18, its him!

maybe one day i will get there.. :sunny:
 

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I have seen about 50 STIs dyno with bolt ons and have never seen numbers much over 300Whp. Never! I guess it really depends on the dyno but even high reading dynos only generally do 310whp and 330wtq. Max. The turbo will only make about 22psi max and 18 or lower at redline. On a stock STI the turbo is maxed out. On an STI with bolt ons the turbo is not effiecient. Any turbo that can't hold boost to redline is to small. Even a FP green spools faster and makes more power then the vf39. If you want mid 300Whp effieciently look at a bigger turbo. Most people throw around numbers with there turbo maxed out on meth or race gas. If you want this on a daily driver with no meth go with a gt32 or something. gt32's are cheap and will make the power. On a ej22t with wrx heads it will make 30psi at 3500... And hold it all the way to redline. Trust me! :)
 

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Discussion Starter #14
I don’t want to run that much boost. I honestly don’t want to run over 20psi if I don’t have to. I would rather build the power through timing rather than boost.
 

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Brydon said:
I have seen about 50 STIs dyno with bolt ons and have never seen numbers much over 300Whp. Never! I guess it really depends on the dyno but even high reading dynos only generally do 310whp and 330wtq. Max. The turbo will only make about 22psi max and 18 or lower at redline. On a stock STI the turbo is maxed out. On an STI with bolt ons the turbo is not effiecient. Any turbo that can't hold boost to redline is to small. Even a FP green spools faster and makes more power then the vf39. If you want mid 300Whp effieciently look at a bigger turbo. Most people throw around numbers with there turbo maxed out on meth or race gas. If you want this on a daily driver with no meth go with a gt32 or something. gt32's are cheap and will make the power. On a ej22t with wrx heads it will make 30psi at 3500... And hold it all the way to redline. Trust me! :)
sounds good, i was thinking about doing a setup like this eventually, except use an ej22e deck with new turbo legacy pistons + 98 DOHC RS heads, but doesnt driveability suffer?

and doesnt the gt32 require custom flanges for the up/down pipes?
 

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99' Subaru Impreza 2.5 Rs
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yeah thats why the guys at tuning factory were surprised when they tuned my car and got those numbers. I was told it would be a good day if we got 300 hp to the wheels out of it. It certainly didnt hold that boost till redline.
 

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Discussion Starter #17
mxpunk said:
sounds good, i was thinking about doing a setup like this eventually, except use an ej22e deck with new turbo legacy pistons + 98 DOHC RS heads, but doesnt driveability suffer?

and doesnt the gt32 require custom flanges for the up/down pipes?
Why are you going to use a an N/A block? the 22T's really are not too expensive you can even find them in a junk yard from time to time. Then you already have good pistons/rods. I am sure the block it's self on the N/A 22 could take 300, but the rods may or my not.
 

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amorton said:
Why are you going to use a an N/A block? the 22T's really are not too expensive you can even find them in a junk yard from time to time. Then you already have good pistons/rods. I am sure the block it's self on the N/A 22 could take 300, but the rods may or my not.
ive seen just the blocks off the ej22t going for 1,000+

the ej18,20,22e,22t use the same rods pretty much..

315ish whp is all that i am looking for in the long run of things, and i told myself im not gonna spend more then 4-5K once its all said and done.. :loser:
 

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I ran a vf39 on an 22t shorty with rs heads and a pp6. I dynoed at 242 whp up with harvey at superru pair. I trapped a 106 at bandi with that at 16 psi. I was only holding like 12 psi at redline. Stock sti's do 215 whp on that dyno
 
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