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Old 09-02-2008, 02:21 PM   #1
VIsubi
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Default 06+ 2.5i turbo charging

Seems that a few people on here say that the 2.5i can't be turbo'd but for the record it can be turbo'd and the piggyback ECM works just fine with this sytem and its ECU(AVO tech's explained this to me when I called) the heads flow alot better than a wrx,tranny is the same minus the final drive ratio and clutch. There is no need for modifications with 06+ imprezas still mounts up like pre 06 kits do. See as so many disagree explain why you figure this as your answer...also yes a 3mm head gasket from HKS which does bring it down 1.2 points will work at bringing compression down but does little to boosting pressure. This for the reason of using forged pistons which will be a later add on for me rods are the same as the wrx..don't beleive do some research. Who here as turbo charged your 2.5i
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Old 09-02-2008, 03:35 PM   #2
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Noone said it couldn't be done, they said its not smart, and to some extent with the stock engine thats true. The tranny is NOT the same. And the rods aren't the same either.

I think you are the one who should do some research. Prepare to be flamed
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Old 09-02-2008, 04:16 PM   #3
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Could you explain what 1.2 points means in terms of compression? Considering it's a ratio, you can't just change the numbers in a linear manner (going from 9:1 to 6:1 is not the same as going from 6:1 to 3:1).

Also, would you please post up at least an explanation of what you did to calculate the change and what the actual compression ratio will be after adding said gaskets? By the way, asking somebody in this case doesn't count unless they have a damn good resume`.

Also, mind grabbing a WRX VIN and a 2.5i VIN and proving that the connecting rods are the same part number? I don't doubt it (really), but i don't know for sure.




I actual think successfully turbocharging a 2.5i would be easier than previous years, with one caveat;

The pistons are made, as of '06, with what's called "hypereutectic" silicon/aluminum alloy. This means that there is more silicon in the mix than can actually be alloyed into the metals crystalline structure. I believe for aluminum/silicon this is something like 30% silicon by molar quantity. The result is that there are bubbles or pockets of pure silicon, supported by a honeycomb of aluminum. This makes a very lightweight, wear resistant piston (which, by the way, is probably forged as stock - The stuff is a pain in the balls to machine). The downside is that it is very brittle. Brittle pistons mean you need to increase your margin of error to avoid knock like the plague, as it will very quickly shatter your pistons. With the minimal amount of boost already possible on pump gas, you quickly limit the amount of boost you can effectively run. It also means your tune has to be excellent, and your boost control and fuel control need to be better.

Luckily, the newer ECU does support tuning easily, so new injectors (not that silly 5th inector) aren't too hard to accommodate.



I am tenatively planning on turbo'ing my car eventually (probably not for a few years), and i definitely think it's possible to do well (again, better than the older cars). However, it'll require a bit more finesse and thought than the older engines to prevent damage.
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Old 09-02-2008, 04:32 PM   #4
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Any car can be turbo'ed. Its just important to think about the total cost vs the final power output. You can make more power for less money by swapping engines IMO.
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Old 09-02-2008, 04:44 PM   #5
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Not nearly as interesting though. Besides, a turbo'd N/A car would make a better autox car than the turbo motor.


You just have to know what you're after, and what your plan's limitations are.
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Old 09-02-2008, 07:14 PM   #6
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lol, I just wrote a long write-up of what I would do, check the original post back in the naturally aspirated thread.
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Old 09-02-2008, 07:57 PM   #7
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Quote:
Originally Posted by sniper1rfa View Post
Not nearly as interesting though. Besides, a turbo'd N/A car would make a better autox car than the turbo motor.
Yes, I have thought about this extensively. Unfortunately it's bumped straight to SM, where 200whp is simply laughable.

Does WRX plumbing bolt up to the 2.5rs/i motors?
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Old 09-02-2008, 07:59 PM   #8
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Quote:
Originally Posted by ProDarwin View Post
Does WRX plumbing bolt up to the 2.5rs/i motors?
Yup, but you'll need to get a wrx crossmember/notch yours.
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Old 09-02-2008, 08:57 PM   #9
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Quote:
Originally Posted by ProDarwin View Post
Yes, I have thought about this extensively. Unfortunately it's bumped straight to SM, where 200whp is simply laughable.

Does WRX plumbing bolt up to the 2.5rs/i motors?
*shrug*
I just got bumped into modified in the local rallyx's in a stock 2.5i. I don't expect to come anywhere near placing, but i don't think the divide is that large. Then again, autox may be more competitive.

Is 200whp really that little, when you're able to put it down so much sooner? I mean, it's still 10:1, so you've got quite a lot down low for a turbo. Maybe not as good as a supercharger, but thats a different animal.
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Old 09-03-2008, 04:48 AM   #10
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2.5i rods same as 2.5l wrx? I don't think so.
Shortblock on the 2.5l wrx & sti are the same.
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