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Old 12-17-2003, 01:37 PM   #1
serious
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Default Yet another 2.0 to 2.5 sti block ?

Yes, i know it can be done. Yes, i know pretty much what it takes (well most everything anyway) .
But, what i don't know is how the engine would take to basically being stock. Yeah, take a stock 2.0 wrx engine and just swap the 2.5 block in place of the regular 2.0. What kind of performance would you get? Would it be safe with the current injectors to do this? Or would i want to upgrade to at least the sti injectors/bigger turbo and all that?
What i want is something that has some more torque, but not so much as the snap the transmission like everybody keeps saying it will.
Any ideas? The i speed write up doesn't say which turbo they used or much like that.
Thanks
Brent
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Old 12-17-2003, 01:46 PM   #2
mlambert
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I dont think anyone would be doing much more than guessing. Most likely if you were to tune it to around 250whp (or less) you could use the stock injectors.
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Old 12-17-2003, 04:11 PM   #3
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It's being done: http://www.cobbtuning.com/impreza/engineblock3.html

I'm sure it can be done without all the stuff that Cobb does to the shortblock. Maybe Cobb would be willing to share some info w/ you if you buy some stuff from them.
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Old 12-17-2003, 05:00 PM   #4
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I don't think we're on the same page. What i was thinking about doing is taking a completely stock 2.5 sti block and mating in to my completely stock wrx heads and leaving everything else untouched on the car.
But, that coob block does look sweet!
Brent
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Old 12-17-2003, 05:02 PM   #5
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Quote:
Originally posted by ITWRX4ME
It's being done: http://www.cobbtuning.com/impreza/engineblock3.html

I'm sure it can be done without all the stuff that Cobb does to the shortblock. Maybe Cobb would be willing to share some info w/ you if you buy some stuff from them.
you are talking about a completely different block then he is asking for.
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Old 12-17-2003, 05:04 PM   #6
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Block with mismatched heads = disaster. Ask the LS VTEC guys, bet they'll agree.


Full_Clip recommends not doing this project.
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Old 12-17-2003, 05:11 PM   #7
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i'm interesting about 2.5 sti block with stock head, keep us update!
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Old 12-17-2003, 05:14 PM   #8
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There was one guy that did the swap and just used his stock heads with the 2.5L block. I just got done with my sti block swap (250 miles so far) but I used V8 RA heads...
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Old 12-17-2003, 09:37 PM   #9
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Dang, wish i had some ver. 8 heads laying around.
Brent
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Old 12-17-2003, 10:20 PM   #10
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Initially we used a USDM 2.5 STi short block, Stock USDM 2.0 WRX heads, helix up pipe, 3”turbo back, VF 30, I-Speed ECUtek at 15psi (Represented by the BLUE line)

The RED line was the same car with a USDM 2.0 short block, Stock USDM 2.0 WRX heads, helix up pipe, 3”turbo back, Stock Turbo, I-Speed ECUtek at 15psi

Needless to say, I have had a stock STI short block with wrx heads on my car for about 4000 miles now.

Currently we have put a 20g and 565’s on the car. It now makes max torque (~ 279) by 3500rpm and hits max whp (278ish) by 6500 rpms. Whoever thinks that this set-up will not work…well…come on over and get a ride

Happy Holidays,

Chris
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Old 12-17-2003, 10:25 PM   #11
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Quote:
Originally posted by Full_Clip
Block with mismatched heads = disaster. Ask the LS VTEC guys, bet they'll agree.


Full_Clip recommends not doing this project.
I have an ej22 block that is bored, stroked, and sleeved with wrx heads, and ej25 head gaskets. My motor is perfect. You cannot compare honda b series engines to the subaru ej series. Not even close. I personally know one person for every favorable block/head combination there is. Everyone of them runs good.
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Old 12-17-2003, 10:30 PM   #12
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So you only gained 41 horsepower and 35 pounds of torque with a vf30 and a 2.5 block? ? Shouldn't you be able to gain that with just the turbo upgrade?
With that kinds of gains it doesn't really sound like you gained much of anything. Am i misssing something here?
Brent
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Old 12-17-2003, 10:33 PM   #13
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Looks like it has been said here already but...

The 2.0 heads work fine on the 2.5 shortblock. I've even seen it used on mildly modded ones.
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Old 12-17-2003, 10:34 PM   #14
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Quote:
Originally posted by serious
I don't think we're on the same page. What i was thinking about doing is taking a completely stock 2.5 sti block and mating in to my completely stock wrx heads and leaving everything else untouched on the car.
But, that coob block does look sweet!
Brent
The stock turbo and what not would be way past its limits on a STi block.... It would awaste of the STi block, the stock wrx tubo isnt worth its weight, the stock injectors are pushing it on a stock turbo..... You get the point right? Sure you can run it on the $1300 bock and all the work you put into it but why?

Quote:
Originally posted by Full_Clip
Block with mismatched heads = disaster. Ask the LS VTEC guys, bet they'll agree.


Full_Clip recommends not doing this project.


Full_Clip needs to go and read the conversion forum FAQ
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Old 12-18-2003, 12:07 AM   #15
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Chris

What kind of boost you running on the 20g.
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Old 12-18-2003, 01:38 AM   #16
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Swapping blocks and heads like an LS/Vtec WILL work if you do it right, just like with any other motor set-up. If you do it right, it'll last.
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Old 12-18-2003, 02:27 AM   #17
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Quote:
Originally posted by serious
So you only gained 41 horsepower and 35 pounds of torque with a vf30 and a 2.5 block? ? Shouldn't you be able to gain that with just the turbo upgrade?
With that kinds of gains it doesn't really sound like you gained much of anything. Am i misssing something here?
Brent
The I-Speed setup is not about max power. The 2.5 liter shortblock mainly gives the low end a kick in the pants.

Many people have gotten really big power from this setup, but they've almost always chosen JDM STi heads.
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Old 12-18-2003, 09:24 AM   #18
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Quote:
Originally posted by fogdor
Many people have gotten really big power from this setup, but they've almost always chosen JDM STi heads.
Or ported the stock USDM heads, got the bill and wished they had just bought JDM STi heads.
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Old 12-18-2003, 09:48 AM   #19
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Quote:
Originally posted by serious
So you only gained 41 horsepower and 35 pounds of torque with a vf30 and a 2.5 block? ? Shouldn't you be able to gain that with just the turbo upgrade?
With that kinds of gains it doesn't really sound like you gained much of anything. Am i misssing something here?
Brent
I don't know the exact specs of what they are running but I believe both tests were running off the stock injectors. Hence the reason they were running 15psi on the VF30, when stock on the STI it runs in the 17psi range. The curve is the important thing, and that you are missing because it's right there, and I'm not sure how you could miss it. At 3000 rpm he's making ~35-40 ft-lbs more torque with the 2.5 setup than the 2L and stock turbo. If you look at dyno graphs from TurboXS and their Stage 4 setup, the VF30 generally makes less torque at 3000 rpm than the stock turbo. I-Speed's setup makes more torque everywhere, with a much larger turbo.
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Old 12-18-2003, 12:36 PM   #20
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So basically with stock heads you're not going to get a ton of horsepower correct? What would be good guess with 2.5 block-2.0 heads and the vf30/34 with sti injectors turned up to a safe boost level?
I'm not going for max power on my car. I want the torque of a bigger engine and i want it everywhere, not just at redline.
Thanks for everyone's input.
Brent
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Old 12-18-2003, 12:41 PM   #21
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Quote:
Originally posted by Full_Clip
Block with mismatched heads = disaster. Ask the LS VTEC guys, bet they'll agree.
Not really. (I was one of the first group to do it)

The problem in that case, was that the block was the weak link with a nice head. In this case, the head is the weak link with a strong block. But I'd rather have a strong bottem end with a head that doesn't flow that well than vice-versa.
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Old 12-18-2003, 12:54 PM   #22
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Is anyone making a cam yet that would do better than the stock cams for this setup? I know you can put in the sti cams with somework, but i don't know what all the requirers.
Somebody could make a nice little chunky of change by developing some nice cams and maybe upgraded valves/valve parts.
Brent
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Old 12-18-2003, 02:56 PM   #23
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JUN offers cams and valvetrain components. Unfortunately they're expensive
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Old 12-18-2003, 03:17 PM   #24
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So does Cobb
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Old 12-18-2003, 04:19 PM   #25
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Quote:
Originally posted by MAD REX
So does Cobb
rewelds, and while thier are few reports of problems and a lot of the questionable. I wouldnt chance it with a set of $2k heads....

Quote:
Originally posted by serious
So basically with stock heads you're not going to get a ton of horsepower correct? What would be good guess with 2.5 block-2.0 heads and the vf30/34 with sti injectors turned up to a safe boost level?
I'm not going for max power on my car. I want the torque of a bigger engine and i want it everywhere, not just at redline.
Thanks for everyone's input.
Brent
The stock wrx heads on an STi block will be good for 300+hp, about the same as the usdm STi( 19 psi I think.) The jdm sti pink injectors are bigger then the usdm side feeds 550 vs 480. This set up will give you more torque then you know what to do with....
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