How much boost can the stock internals take? - Subaru WRX Forum
 
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#1 Old 11-13-2008, 12:04 PM
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How much boost can the stock internals take?

I have a 2003 WRX and I am looking to make some changes. I am looking at getting an STI intercooler because I was told that they are good option if you don't want a front mount. I am considering getting a VF22 Turbo and run 18 psi with a Perin up and down pipe. Would I need to worry about changing the injectors or hurting any internals with those mods? Thanks
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#2 Old 11-13-2008, 01:19 PM
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You need to do some more research.

The STi TMIC is not a good option if you want to go with a fairly large turbo. It's good for an STi sized turbo (VF39) but it's still fairly limited. There are larger aftermarket intercoolers out there from Perrin, APS, and others. You don't have to get a front mount to get something bigger than the STi intercooler.

The VF22 is not that great a turbo. It was popular early on because it was one of the few turbos that used the WRX's layout. Now, there are a plethora of turbos out there. I would recommend an E3-16G turbo. It will cost less, spool much faster, and get similar peak numbers.

18 PSI is just a number. Power is proportional to airflow, not boost pressure. I suggest you find a good tuner who can work with whatever setup you get and come up with a good, safe, and powerful tune. I would not have any specific boost pressures in mind for what that means.

Your injectors are very small and barely enough for the stock turbo. If you go with a substantially larger turbo, you must change the injectors as well as the fuel pump so that you have enough fuel capability to actually increase power. 650cc is appropriate for an E3-16G. Different turbos may require more or less.

The EJ205 handles additional boost and power very well. It's quite happy in the 300whp range. I wouldn't worry too much about internals unless you start messing around with more aggressive mods than a bolt on turbo swap. The part of your car that's most likely to break from these mods is the transmission, not the engine. The stock 5-speed is pretty weak and many people have problems at stock power levels let alone something twice as high.

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#3 Old 11-13-2008, 03:47 PM
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Quote:
Originally Posted by mosc View Post
18 PSI is just a number. Power is proportional to airflow, not boost pressure. I suggest you find a good tuner who can work with whatever setup you get and come up with a good, safe, and powerful tune. I would not have any specific boost pressures in mind for what that means.
Word. A lot of people I hear always asking how much psi should I run with this setup or whatever, get it tuned safely for your setup, the tuner should know what psi to tune it at with your mods. Don't go in there and tell him you want it tuned @ this specific psi...

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#4 Old 11-14-2008, 10:14 AM
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I often hear people mentioning PSI too as if it were the biggest turbo-related issue to worry about. And it might be in some cases, but not so much in the Subaru world. For many Subaru owners, it is common knowledge that manual boost controllers are generally a bad idea (unless you really know what you're doing, etc.). I think most people's boost-number-paranoia stems from the fact that older/other turbocharged cars many times require a manual boost controller and nobody wants to destroy their engine by setting their boost number too high. Subarus don't necessarily need a boost controller because the ecu can usually handle regulating boost if tuned properly.

As an example, let's say you turbocharge a naturally aspirated Civic engine. 7-8 lbs of boost might be a really high number for that engine. Any more than that could damage gaskets, etc. On a WRX/STi, 17/18 lbs of boost is not an uncommon number for an average/reliable Stage 2 setup. It's sort of like comparing apples to oranges.

John
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#5 Old 11-17-2008, 12:48 PM
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Yeah I have been looking at the greddy turbos and I have been thinking of the 16G or the 18G. But I think that the 16G will be enough for what I am wanting to do. I had a buddy that ran the VF22 in his 02 WRX and that thing ran GREAT. Other than that I have decided to get the Cobb Accessport since you can make your own custom tunes.
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#6 Old 11-17-2008, 06:40 PM
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Wrong....they're only custom tuned if you have the AccessTuner Race (Read: Street tuner software) or have a pro tuner use their ProTuner software on the maps. Btw, I'm just correcting here...not trying to be a dick. But, there are normally 3 distinct 16G setups. 16G, Big 16G, and EVO III 16G. Even still...they're not all the same. They vary from in flow rates, PSI, and what not....depending on who made it.
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#7 Old 11-18-2008, 11:24 AM
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Yup. With the COBB AP, I beleive they have a map for a 16G turbo, but it has to be the small 16G, not the Big or the EVOIII 16G.

Another thing you need to look at is the turbo's supporting mods. Don't cheap out on anything. Get a Perrin or APS TMIC, or even a FMIC if you want, and; if you don't have them already, you'll need your fuel system, and I highly recommend a catless Up-Pipe and a bellmouth Down-Pipe (catted or cattless doesn't matter) The Perrin UP will help not destroy your new turbo, and I don't think Perrin makes a DP..... (Never mind I found it, they sell it in two seperate pieces that are $300 each! Why so expensive!? Oh, it's catted.)

Holy crap, if you don't have a cat-back exhaust and want one, perrin is having a huge sale! Perrin Performance - Cat-Back Exhaust Twin Tip only $389 for a twin-tip sleeper exhaust! Man that's a deal......

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#8 Old 11-29-2008, 12:04 PM
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I'll add my .02 cents.

Stop thinking there are magic PSI numbers. 18psi with a shotty tune will blow ringlands in 10 minutes.

Comes down to the tune..........period.


I have been hunting in my head for verbiage like this forever.......
"Power is proportional to airflow, not boost pressure."

Meth'd, EWG'd, Str8 Cut PPG'd, 20G'd Bug-i, 354awhp and 315tq SAE 5 Corrected 50/50 meth @ 19-20psi.
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