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Discussion Starter · #1 ·
one cannot beat just dropping in a factory motor for say 1300 $ or so. It will spool those stage 4 WRXs like stock or better! We are testing out the results of STi 2.5 and WRX heads with USDM STi cams... that would be an awesome semi cheap upgrade.

-Mike (MJU1983) :wiggles:
Let's get this discussion going. Please keep it on topic, and try not to suggest other ways to achieve similar power and turbo spool-up results. I'm going to PM MJU1983 and All8up to get their participation.

Initial questions...

What exactly comes with an STi block?

What other parts would you need to make this happen?

Would a custom UTEC map be sufficient engine management?

Is a VF30/34 too small for this application?
 

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What exactly comes with an STi block?
Shortblock includes: Case 2 parts, crankshaft, including main and rod bearings, rods, pistons. Everything is assembled.

What other parts would you need to make this happen?
New headgaskets, new headbolts or head studs.

Would a custom UTEC map be sufficient engine management?
Yes you can tune with any EMS that is out currently.

Is a VF30/34 too small for this application?
Yes, BUT it would spool so quick its not even funny. You should test this out with your stage 4+ and see how happy you are with the results.

-Mike
 

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Yeah, this is a path I've strongly considered after some more time goes by.

How does the VF30/34 compare with the turbo that the USDM STi comes with? (VF39?) If the 34 is a little on the small side, what would be an appropriate turbo to give a mild kick in the pants to the 2.5liter? The 34 is a nice mild upgrade to the 2.0, what's the analogous turbo that you could use to get a similar upgrade to the 2.5?

Am I making any sense?:confused1
 

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MJU1983 said:
Shortblock includes: Case 2 parts, crankshaft, including main and rod bearings, rods, pistons. Everything is assembled.



New headgaskets, new headbolts or head studs.


Yes you can tune with any EMS that is out currently.




Yes, BUT it would spool so quick its not even funny. You should test this out with your stage 4+ and see how happy you are with the results.





-Mike



In addition, I would consider getting head work done. Since you have to remove the engine to perform headwork, you may as well use the down time to send the heads off.
I do not have conclusive information that a stock WRX head w/ stock cams would facilitate the sti block swap. Someone else would have to chime in on that.

You can opt to use an STI headgasket, but it will put your compression to 9.1, otherwise I believe you can use a 2.5 RS head gasket to get it down to 8.5.1 (from memory).



Unfortunately, I have not been able to get a base map for my utec to get me a starting point.


I would certainly opt for something larger than anything in the VF line up. I-speed's dyno showed how quickly the VF30 was maxed out on the STI block. If you are going to go through the trouble of this swap, you may as well get a turbo that would compliment the set up.
 

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Discussion Starter · #8 ·
All8up,

What turbo are you going for?

I'm thinking that a PE1820 or something would be pretty good in my situation, as I would like a load of power, but not much more lag than a VF39 would have in an STi.

What are you doing with your heads - aren't they from a 2.0l WRX?

My STi injectors would probably be maxed out by an upgrade like this. Are they the same ones that come in a USDM STi? I guess that PE 6**cc injectors would be more appropriate here.

Would a higher or lower compression ratio be better for this project? Lower would probably compromise power when not in boost, right? And higher would somewhat limit the amount of boost that you can run?

What's up with these shims? I think I read somewhere that the '04 WRX heads may be different than older ones. Is there really a difference, and does it matter here?

Anyone else, feel free to chime in.
 

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Good question about the injectors. What's the biggest turbo you're going to be able to run on stock STi injectors; VF34?
 

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SBW said:
Are USDM STI cams available yet?

Do you need the shim under bucket design or shimless design for these?
I bought the shimless buckets from Ron. The USDM cams are available through Subaru parts departments now.

I'm using a 20g TD05 w/ 8cm2 exh.

Yes the head that I am using is off a USDM WRX.

As far as injectors are concerned, why don't you try that mod that people are doing to get the stock injectors to flow to 700c.
 

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If you design the piston properly you can go up in compression ratio. I would always change the pistons and rods personally just to ensure safe 450 whp power. The VF34 is a poor choice for that kind of motor. ON the STi, the VF39 which is about same size is a dud and can not maintain boost. I would go for at least a VF22 minimum but personally I think a GT30R or the like would be the best choice for an everyday car.
 

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Discussion Starter · #12 ·
All8up said:
I bought the shimless buckets from Ron. The USDM cams are available through Subaru parts departments now.

As far as injectors are concerned, why don't you try that mod that people are doing to get the stock injectors to flow to 700c.
What exactly are shimless buckets, compared to what is in my WRX motor?

How do the cams differ from the crankshaft?

I like the injector idea, because I'd probably trash them anyway if I moved up to PE injectors.

Dan, what do you have to say about the good old PE 1818 and 1820 turbos these days? I already know the benefits of your turbos, but I have yet to find the downside of the PE's. At very least, what's the price comparison?
 

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Probably, but just in case:

Crankshaft -> center of engine. Connecting rods directly attach to it, which have pistons on the other end.

Here is a pic (not of ours, just what a crankshaft is):



Or one like ours:



A cam is a rod with egg shaped nodes on it...opens/closes valves.

A pic:



VV

Mili727 said:
Are you kidding me?
 

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Discussion Starter · #16 ·
Mili727 said:
Are you kidding me?
If you F up this thread or take it off-topic, I will do everything in my power to have you banned.

Anyway, what's wrong with the cams that come in the WRX engine? Aren't they part of the heads?
 

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Bask Oner said:
How do the cams differ from the crankshaft?
Not sure if this is what you were asking but ...

cams- turn and open and close the valves in the head in a specific time . located in the heads

crankshaft - is at the bottom end. Pistons are installed to this piece and it turns as the pistons go through their cycles. backside of the crank turns the flywheel.

that's as best as I can explain it.
 

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Bask Oner said:
If you F up this thread or take it off-topic, I will do everything in my power to have you banned.

Anyway, what's wrong with the cams that come in the WRX engine? Aren't they part of the heads?
I was just noting the fact they use USDM STI cams instead of the ones that come stock on our WRX's. I have read many times over that one of the main problem with our engines(WRX) is that they cannot breath up top.

USDM STI cams could be a great alternative to expensive Jun cams, so I was just wondering how they installed them.
 

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Bask Oner said:
If you F up this thread or take it off-topic, I will do everything in my power to have you banned.

Anyway, what's wrong with the cams that come in the WRX engine? Aren't they part of the heads?
Haha calm down matt.

The stock WRX valvetrain is what will hinder your rev limiter. Upgrade your valvetrain and you can rev higher.
 

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Partly correct. Valvetrain can hinder rev limit, but what is being discussed here is how the stock cams limit top end flow. They choke off the bigger turbos.

VV

Mili727 said:
Haha calm down matt.

The stock WRX valvetrain is what will hinder your rev limiter. Upgrade your valvetrain and you can rev higher.
 
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