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Old 04-20-2004, 11:58 AM   #1
Ishamiyal
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Talking 2.5RS Turbo issues

K, lemme make a long story short as I was already discussing this in a somewhat dead thread. I bought a 2001 RS 2.5 4 weeks ago, and turboed it out with the stock TD04 and TMIC off my 03 WRX. I made all the mounts, up/down- pipe, flanges, intake, etc. and installed a complete Greddy E-manange system and PRofec-B II boost controller. I also put in the WRX fuel pump and 400cc injectors.

After talking to many people about the stock internals, it was apparent that my TTL was prolly gonna be short, even with moderate boost levels. So I was at Prestige Subaru in Asheville, SC yesterday to get sparkplugs and tranny oil- and they had 2 STI shortblocks in crates. So, after hearing all the horror stories of exploded pistons, and knowing the cost of the stroker kits, I plopped down the $1350 for the shortblock and went home with my new STI motor.

Now heres the questions:

1. I have been told the water crossover may not fit- any info ?

2. Does anybody know what the compression ratio will be with stock 2.5 heads and how to calculate this ? I have been told it should be around the same as the STI because the chambers are the same size in the 2.5 heads.

3. I plan on putting a VF22 turbo on this baby (already have one) cuz I can now push a lot more boost safely. Does anybody know of some oversize injectors I can use that will fit the 2.5 stock manifold ?
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Old 04-20-2004, 03:25 PM   #2
squirrelmasta
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can some one change this guy from a newbie to CRAZY GUY!!!! that is a lot of work there.
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Old 04-20-2004, 03:52 PM   #3
ilmaestro
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Quote:
Originally posted by squirrelmasta
can some one change this guy from a newbie to CRAZY GUY!!!! that is a lot of work there.
No kidding.

Quote:
Originally posted by Ishamiyal

3. I plan on putting a VF22 turbo on this baby (already have one) cuz I can now push a lot more boost safely. Does anybody know of some oversize injectors I can use that will fit the 2.5 stock manifold ?
It depends on what you mean by oversize. Many people use RC engineering injectors, which you can get in different flow rates, 440, 750... etc. I believe Graham is currently using the 440s with his STi block and is moving to the 750s. You could also use STi injectors (I think).

jonathan
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Old 04-20-2004, 04:38 PM   #4
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RC injectors need a spacer for the fuel rails and a different harness. I'm pretty sure all that either comes with the injectors or you can get them from RC. I'm not sure about how they seat in the manifold though. I know my 440s may sit too far back.

-Brett
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Old 04-20-2004, 09:49 PM   #5
Ishamiyal
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K,

I went to RC's site and did their worksheet on fuel injector size. According to their little equation, I need almost 700cc injectors if Im gonna run 80% duty cyle @ 43 PSI. That is also assuming BFSC of .60 and a target of 350 crank HP. However, if I go higher in pressure on the fuel rail and run @ 85% duty cycle, I can get that number down to 553cc which would allow me to use some STI injectors I have. Does anybody know what the maximum fuel pressure the STI 550cc injectors can handle ? I need to be able to run about 60 PSI. 65 would better, cuz I could get the duty cycle back down to 80. I know this would require a new fuel pressure reg, but that is substantially cheaper than the extra 800 bux Im gonna have to drop on injectors.

Any thoughts ?
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Old 04-20-2004, 10:10 PM   #6
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Quote:
Originally posted by Ishamiyal
Any thoughts ?
If you need even more fuel, mod stock WRX injectors. They end up around 740-850cc. Cheap and big. Make sure they will fit correctly in your manifold though...

-Charlie
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Old 04-21-2004, 09:23 AM   #7
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Remember that when you get into boost, fuel pressure will rise. So 43psi is not an accurate reflection.

For instance in my WRX, each lb of boost gives 1 psi of fuel pressure. So with a fuel pressure of 37psi at vacuum, and full boost of 16lbs, I get 53psi of fuel pressure at full boost.

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Old 04-21-2004, 10:48 AM   #8
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you may want to change that 80 to a .8
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Old 04-21-2004, 11:16 AM   #9
Ishamiyal
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Quote:
Originally posted by wcbjr
Remember that when you get into boost, fuel pressure will rise. So 43psi is not an accurate reflection.

For instance in my WRX, each lb of boost gives 1 psi of fuel pressure. So with a fuel pressure of 37psi at vacuum, and full boost of 16lbs, I get 53psi of fuel pressure at full boost.

K,

so if I get new fuel pressure reg- which Im gonna do- can I set a static pressure rather than use a rising pressure, or do I just set the reg to be a certain PSI @ X pounds of boost ?

In either case, what is a safe PSI for the STI 550cc injectors ? 60 PSI is what I need @ full boost cranking out 350 HP @ 85% duty cylcle using the STI injectors- according to RC that is. Will pressure this high have an adverse affect on injector life expectancy ? The STI makes 300 @ the crank, so the injectors are relatively close to that pressure I would assume.
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Old 04-21-2004, 04:41 PM   #10
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Quote:
Originally posted by latinskllz
you may want to change that 80 to a .8
Ah crap, wrong pic. Haha. Move the decimal a couple places.
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Old 04-21-2004, 09:28 PM   #11
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K,

I have scored a 99 RS 2.5 intake manifold from a guy that was reading this post- which essentially allows me to use my JDM 550cc injectors. Im still lookin' for some input on fuel pressure at the injectors. Does anybody think 60 PSI is out of the question with an after-market fuel reg ? I asked RC in an email and they didn't/have not replied.
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Old 04-22-2004, 03:33 PM   #12
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assuming this were to be done on a n/a completely stock RS would anything else have to be changed other than the block? (like anything electrical etc.)

also does anyone know the legality of this in california? i know our smog laws are quite crappy :-/

Last edited by MeshmeZ; 04-22-2004 at 04:23 PM.
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Old 04-22-2004, 05:24 PM   #13
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Well, I geuss the 1st question is why would you change the block on an N/A engine to a low compression block if you didnt plan to turbo it ? There really would be no gains, and in fact you would lose power due to the compression loss.

Im going to assume that I am misunderstanding the post and that you mean if you were to do this with the 'intent' of turboing a stock N/A RS2.5, would you have to change anything electrical? The answer is pretty much, yeah, you do have to do at least some minimal electrical work. Even if you keep boost low enough to the point that you think the injectors dont need to be changed, and you dont wanna mess with timing advance, or use an electronic boost controller(none of which I recommend), you still have to do something about the presence of boost in the manifold- your MAP/MAF sensor is gonna read that, and the ECU is gonna cut fuel. So at the very least, your gonna need some electronic device to fool that particular sensor. I used the Greddy E-manage cuz I didn't wanna have to pay 3-4 times as much for something like a full blown LINK ECU. It doesn't have all the bells and whistles, but is far better than most of the crap that comes with most so called kits- AVO exlcuded. It allows you to program your own maps for MAP/MAF, timing, additional injectors, boost etc. That is if you buy all the harnesses and sensors- which I did. I also have a notebook mounted in the car to tune with- this is a plus for any programmable setup, but not necessary- any computer will do. Mine runs through the stereo, plays DVDs, MP3s, GPS, etc. so there are more reasons I went to the trouble of mounting it. The nice thing about the Greddy E-Manage was that even though you have to splice it into the engine harness, I found how-tos online and got it done in a few hours. www.mohdparts.com has a great section on how to do it and everything is already translated into English from Japanese- the instructions were somewhat unwieldy in Jap.

As for Cali smog I dunno know. There are no vehicle inspections or smog inspections in SC where I live, so we are pretty much free to do whatever we want. I run rich and catless on the streets everyday.
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Old 04-22-2004, 06:17 PM   #14
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Quote:
Originally posted by Ishamiyal
Im going to assume that I am misunderstanding the post and that you mean if you were to do this with the 'intent' of turboing a stock N/A RS2.5, would you have to change anything electrical?
thats ALMOST what i meant. I do mean with the "intent" of turboing later on, but what i wanted to know is other than turbo related stuff is there anything that has to be changed.

so i guess pretend im crazy and i want to put the STi block on the completely stock engine, is there anything i would have to do other than bolting it on? is there anything that has to be changed for THE BLOCK install, nevermind turboing.

i know once the turbo goes on there, there is a whole new set of things to do
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Old 04-22-2004, 06:33 PM   #15
Ishamiyal
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Ok,

well the compression issue- you'd be going from almost 10:1 to almost 8:1, and there would be a huge power loss. Also, you might be fairly rich in the A/F mix because of the lack of air in the cylinders.

As for bolt up, it depends on what year RS you are talking about. I think the intake manifold on certain years may present issues- I am not familiar enough with bolt to bolt, year to year issues, but for the most part, it should bolt right up. You may have noticed at the top of the thread that there may be an issue with the water crossover.You will need to change to STI head gaskets, along with all the other ancillary gaskets. That cost me about 130 dollars at the dealership.
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Old 04-24-2004, 06:33 AM   #16
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Quote:
Originally posted by wcbjr
So with a fuel pressure of 37psi at vacuum, and full boost of 16lbs, I get 53psi of fuel pressure at full boost.


So just run 28psi of boost and you'll be @ your target 65psi fuel pressure
that's what your 8:1 cr is for, right
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Old 04-25-2004, 01:08 AM   #17
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Quote:
1. I have been told the water crossover may not fit- any info ?
Hey there... I was one of the first to put a 04 STI block in an RS. There is an issue with the water crossover getting in the way of a PCV valve on the STI shortblock that is not present with the 2001 RS EJ25. The problem was solved by machining the channel and cutting out a chunk of it in order for the PCV valve to clear. Despite the smaller diameter of the crossover after the machining, both sides of the engine stayed at the same temperature, which seemed to indicate that the reduced flow wasn't significant enough to matter.

If you have questions, and dont' mind a long distance call, give Garcia Subaru in Albuquerque a call. 505-260-5155. Ask for Richard... he did my original swap and I think he's even machined three or four more coolant crossovers that people have sent to him since he's done my block.

Good luck with your project... sounds like fun
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Old 04-29-2004, 11:22 PM   #18
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Yes, I ran into that yesterday. I ended up machining out a chunk of the crossover and then welding/brazing a strip of aluminun plate back over the hole I made. Luckily I not only have a vertical mill, but can also weld aluminum. This is NOT the simple swap the guy at the dealership told me it was. When I got the manifold from the 99 RS to fix the 'injector fitting issue', it also had to be machined because there is no hole in the top of the manifold for what I assume is the MAP/MAF sensor. The mount is there, but it doesnt have the hole for the sensor or the screws. I had to mill the surface, bore the hole, drill screw holes, and then tap them.

Then it was on to the fuel rail mod along with the wrx injector mod. The injector mod was relatively simple- I'm not sure what all of the fuss about 'how to' is about on that thread. It took like 25 minutes to do all four and the caps came right off. It's like 11 o'clock here and I need parts for the fuel rail mod so I gotta stop till morning. The engine swap will have taken me about 22-24 solid hours by the time I'm done cuz off all the stupid fabricating I have had to do. It took me 35 straight minutes to weld that plate over the hole in the crossover. ARRGGHHH!!!!

I also ended up scraping my TD04 and just bought a new VF39 to replace it. Hopefully it will all be back in the car by about 1-2 o'clock tomorrow and I will be flying up the highway.
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