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Old 04-23-2008, 09:33 PM   #1 (permalink)
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Hey guys,

Just got done talking to my tuner about upgrading turbos. Im going to be auto crossing this year and told him I'm looking for a quick spooling turbo. We talked vf-39's, 18g's, and then we got on subject about upgraded IHI turbos such as the vf34 or the twin scroll vf22.

He said personally he would suggest the VF34 over an 18g saying he could get about 270whp (keep in mind stock STi's make around 200-210 and 20g STi's make just under 300whp on his dyno). His opinion was that an 18g is still to small for the 2.5, saying that he would tune for 20psi on the 18g and it would fall too 12psi by redline. I really trust this guy as he is the prominent Subaru tuner here in CO.

All of the options are going to installed with the following, upgraded topmount, perrin turbo-inlet, ported headers and upgraded up-pipe and the rest is obvious.

Here are the turbo options:
- Ported VF39
- Ported VF34
- Ported 18g

Let me know what you guys think
Joe
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Old 04-24-2008, 02:29 AM   #2 (permalink)
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I always assumed the 18G was a larger upgraded from the VF turbos.

I'm interested in hearing what others say.

-Jay
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Old 04-24-2008, 02:48 AM   #3 (permalink)
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I'm sure Todd will chime in on this one. I know he has (06xt BTW) VF34, STi TMIC, coated STi exhaust manifold, Helix (I think) DP, cobb catback, and an AP. With a tune, his car makes 306AWHP on a (I'm pretty sure) Dynapak. Todd, you wanna chime in here, and fill in the gaps?
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Old 04-24-2008, 10:40 AM   #4 (permalink)
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All of those #'s seem really low to me. I know CO is at a higher altittude but that seems off to me. As for a VF34 vs. an 18G, a VF34 flows around 550 cfm and an 18G will flow 600+ depending on the model and trim. Personally I'd go for a MHI turbo based on power and reliability.
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Old 04-24-2008, 11:07 AM   #5 (permalink)
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For quick spool, nothing is quicker than a ported TD04. It will run out of breath a lot earlier than the turbos you mentioned, but it will have instant acceleration out of the corners on a slow auto-x course. As far as making the power that the 2.5 L boxer has the potential for, your tuner is absolutely right. I would go for the ported TD05-18g.
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Old 04-24-2008, 11:30 AM   #6 (permalink)
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Quote:
Originally Posted by XT06' View Post
Hey guys,

Just got done talking to my tuner about upgrading turbos. Im going to be auto crossing this year and told him I'm looking for a quick spooling turbo. We talked vf-39's, 18g's, and then we got on subject about upgraded IHI turbos such as the vf34 or the twin scroll vf22.

He said personally he would suggest the VF34 over an 18g saying he could get about 270whp (keep in mind stock STi's make around 200-210 and 20g STi's make just under 300whp on his dyno). His opinion was that an 18g is still to small for the 2.5, saying that he would tune for 20psi on the 18g and it would fall too 12psi by redline. I really trust this guy as he is the prominent Subaru tuner here in CO.

All of the options are going to installed with the following, upgraded topmount, perrin turbo-inlet, ported headers and upgraded up-pipe and the rest is obvious.

Here are the turbo options:
- Ported VF39
- Ported VF34
- Ported 18g

Let me know what you guys think
Joe
If money is no object, you should go ported 18g (more flow and more power overall). I went w/ the VF39 last time b/c it was $350 used vs. $900-1000 for a brand new 18G. This time I went w/ the 18G b/c I got it brand new for a steal even though it was more than a used VF39.
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Old 04-24-2008, 12:06 PM   #7 (permalink)
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If you go the 18g route, make sure it's the 8cm and not 7cm. Maybe your tuner was talking about a 7cm.
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Old 04-24-2008, 12:53 PM   #8 (permalink)
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Quote:
Originally Posted by sirwilliam View Post
If money is no object, you should go ported 18g (more flow and more power overall). I went w/ the VF39 last time b/c it was $350 used vs. $900-1000 for a brand new 18G. This time I went w/ the 18G b/c I got it brand new for a steal even though it was more than a used VF39.
Agreed.

Several tuners I've spoken with suggested *at least* 18g 8cm for our 2.5.



SW - How much did you picked up your 18g for? I snatched a new Blouch 18/8cm for $800 shipped (seller was asking $899). The best part is it had the polished compressor housing & ported turbine housing upgrades, but didn't list that in the add. Man, talk about a pleasant surprise.
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Old 04-24-2008, 01:10 PM   #9 (permalink)
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One other thing to bear in mind is that you can keep your stock injectors for the VF turbos, but will likely need more flow for your td05h 18g 8cm. not sure how your altitude will play into that though.

18 G is a great turbo - I've driven both an 18g forester and a vf34 (mine), and the power is noticable, although not the difference from the td04 stock to vf34 that i went through.

As for autox, 18G is a bad choice, as is the 34/39/22. Max out your td04 (monster port n polish, full exhaust/headers/up pipe/fuel pump/front mount intercooler - then get a protune and you should be able to get 23 psi by 3K rpm) or run a twin scroll setup (real money) on a vf34 or an 18G
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Old 04-24-2008, 01:11 PM   #10 (permalink)
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For autocross you want power low down, I don't know if i would swap the turbo at all. Also, swapping the turbo will put you in a class against other more highly modified cars. However if you want power I'd go 18g/8cm.
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Old 04-24-2008, 02:21 PM   #11 (permalink)
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Just a FYI.
We just installed the Blouch 18G/8cm on a friends Forester last weekend. It didn't go smoothly. He had to hack up parts of the turbo, hack up up-pipe bolts, and he ruined his inlet pipe.
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Old 04-24-2008, 04:37 PM   #12 (permalink)
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Thank you for the input. IIRC, at least 3 members here are/were running the 18g?

Dave (Integrity Performance). Not sure which manufacturer.

cwepruk. Pretty sure he's running an FP unit.

xtpusa (?) Or maybe that was a 16g.

In any case, I would like to know what's the difference between the manufacturers (Blouch, FP, etc). I thought there's no known issues with these turbos: bolt-on for STi, bolt-on for us.

**My apologies to XT06' for taking this off topic**
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