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Old 07-06-2002, 01:17 PM   #1
DoctorNick
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Default about to take the plunge and buy pistons and rods. suggestions wanted.

facts on my kit:
Custom ej25 turbo kit being built with the help of local i-clubbers who know there stuff.
The idea in the begining was to make a kit that is reliable and will give me enough boost to keep me close to a stock wrx.
Now I am closing on the install date and I think I would like that extra safety feature of having strong internals.

My car: 2002 2.5rs, with an automatic tranny, cobb turbo/NA cams.

Now I decided on J/E pistons with a 100mm bore and they should be ceramitic (sp bad) coating and they should definatly be forged. Now I am fighting what compression ratio I should go for. I could do 8.5 :1 or 9:1 and I will have lower the compresion enough to take away some of the dangers of our high comression n/a motor without loosing all the torque.
Now I understand why people would go 8.5:1 because they are going to run a high boost, high HP application. But for me. I see that all I am going to want is reliable 13s(if its possible). So what do you guys think? Also when I call them, what should I tell them when I order the pistons? Should I say I got a 2000 rs also...because they will assume if I say 2002, that I have a wrx? (trues me, I ran into that problem with RC injectors and ordering from a dealership)

ok, one more question. Rods: Cronner? What do I ask for? What do I look for? Also for the application I am trying to do, what other internals are a must to change? I don't think valve springs are that important because I can't rev any higher then what the ecu is set to. If you guys know of anything else. Suggestions, comments, ideas. They would be great. Thanks.
-Neal
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Old 07-06-2002, 01:38 PM   #2
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I'm thinking that rods would not be a necessity if you aren't going to go all out power, since I don't believe I remember hearing about anybody breaking a rod. pistons should be good to give you a better safety blanket.... at the same time since you're in there might as well replace all of it in case you decide to go faster in the future, but it's all your choice.

sorry I can't help on the tech stuff
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Old 07-06-2002, 02:29 PM   #3
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You will need to pick up new bearings too. You can probably just get regular sized bearings since your crank should not have much milage wear on it. I'm not usre if the stock rods seperate easily from the piston. I haven't looked at them yeah. So do, some don't. Rods usually are not too expensive though and you don't want to have to do it again. Mayb as well pick up some forged rods for it as well. As far as the brand that's all personal preference. THey pretty much all perform the same.

However, from my experience I easily keep up with a stock WRX running 3psi. I have a 99RS. I would personally look into tranny over engine internals in a low boost application. Tranny is a weak link in these cars. Or, if you've got the cash, do both.
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Old 07-06-2002, 02:33 PM   #4
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Well I am thinking of replacing anything that will break under initial stress and under short auto-x's. And heck. I might get a boost bug and want low 13s but i hope not. Realy I don't wanna ask to much from this car. Reliable 13s would rock, but reliable 14s is pretty awsome comming from a stock 18sec auto 2002 rs.

A real monster will be a NON daily driver, but this needs to be a daily.
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Old 07-06-2002, 02:36 PM   #5
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I amnot worried about the tranny because of having an automatic. I am not pushing more then 300hp either. So I am not worried about how the tranny will be. I got a big tranny cooler, I am about to switch to synthitics so I am not worried about that. The motor is my consern.
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Old 07-06-2002, 02:49 PM   #6
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EJ25 will be reliable up to about 8-9psi with no internal mods. If you run say, 6 psi, you will probably be pushing 240 hp and 250 lbs/ft of torque.
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Old 07-06-2002, 02:58 PM   #7
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If your going to do rods and pistons, might as well not do it half assed, and go ahead and get a crank, or get yours done. then, might as well get the whole engine magnafluxed and blueprinted.
Therin lies reliability.
imho
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Old 07-06-2002, 05:56 PM   #8
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Quote:
Originally posted by WRXpkr
If your going to do rods and pistons, might as well not do it half assed, and go ahead and get a crank, or get yours done. then, might as well get the whole engine magnafluxed and blueprinted.
Therin lies reliability.
imho
haha, thanks. Remind me to kick ya in the teef at the next meet. NEways. I am going to get the block blueprinted and balanced. I need to confirm the pricing and I need to find out the o-rining process.
-Neal

Also who can confirm stiguy555's proclaimed 6-8psi statement? Because if that is true. I could go 9:1 and run 10psi and be fine.
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Old 07-06-2002, 09:25 PM   #9
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You don't need to change the crank unless your going to stroke the engine..The crank is virtually bullet proof..That is one of the last things I would ever change..I would use Pauter rods and JE pistons.But that's just me..I know nothing about building horsepower ....Gerry
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Old 07-06-2002, 10:34 PM   #10
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Quote:
Originally posted by Gerry
Pauter rods and JE pistons.
Hmm, ok. so now what do I do when I call up Pauter and ask for rods. what info do they ened to know? Also do I tell them forged? what info do they need to know? Any otehr opinions? What about compressoin? Should I go 9:1? ceramitic coated? Also should I look into oil squarters on the block? Or is that realy for high HP kits. I just ant my reliable 13s.
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Old 07-07-2002, 01:14 AM   #11
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All you need to do is call Pauter and tell them you want rods for a 2.5 . They might have some on hand.They make all of our rods at Z1. If he dosn't have them on the shelf they take around a 4-6 week turn around.Also Pauter only had forged rods. As for c/r..I would go with 8.5:1..Have the skirts done on Moly..and maybe have them gas ported..Gas porting helps with ring seal.And since your on the street you want the gas ports on the sides by the rings, if you had them on top you have a chance of having deposits getting into the ports.You could have the top of the pistons HPC coated,,Thats up to you..Also oil squriters are a nice assition since the case is cracked anyways, It helps cool the pistons,,,Gerry
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Old 07-07-2002, 01:26 AM   #12
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Im doing the same thing with my MY02 OBS, but Im saving up for the Forced Air Tech kit.

After talking to a friend of mine, who used to be an engineer for the Nascar engines, I've decided to go with the following: 100mm forged 10.5:1 (or stock ratio) compression. Ive talked to him about the ups and downs of keeping a high ratio w/ added turbo and he told me that pressure is a problem because it causes knock, but with propper tuning, Intercooling and water injection we could SAFELY run 12-14 PSI. Of course this wouldnt last long, taking its toll on the engine, but with a 60/40 alcohol mix injection Ill be runing continuous 7-9 PSI without a problem. BTW the calculations were made on the 10.5:1 compession base.
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Old 07-07-2002, 10:51 AM   #13
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Hmm, thanks guys. I think I am leaning towards 9:1 compression. But

Quote:
Have the skirts done on Moly..and maybe have them gas ported..Gas porting helps with ring seal.And since your on the street you want the gas ports on the sides by the rings, if you had them on top you have a chance of having deposits getting into the ports.You could have the top of the pistons HPC coated
from what Gerry said...he showed me I need to learn alot more.

Also, I am going to say the horrid word which all hate to hear, which is...
I would like to do this on a budget.

Thats why I thought pistons and rods would be the best...

also what does torque loss of the ej25 at 9:1 feel like?
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Old 07-07-2002, 11:42 AM   #14
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I'm at the same point in trying to figure out how I'm going to make the engine more reliable. You may want to change the springs, retainers and maybe the valves since you have the COBB cams. As far as the ratio I would think 8.5:1 would be good.

I feel like I going to insight a riot by bring this up, but have you thought about the EJ22T/EJ25 hybrid engine too. I'm weighing the options between building the 2.5 and the hybrid, and I still haven't made the decision yet.
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Old 07-08-2002, 03:15 AM   #15
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Do the 8.5:1 as you will hardly notice a diff with your 2.5L motor vs a 8:1 EJ20which is blah on the bottom end. But, you will be able to run 18 psi vs 14 psi when the boost crack get's you addicted, and even if you don't get addicted at 14 psi you will be safer with 8.5:1 pistons. The 10:1 pistons you have should stay under 8 psi, and with any detonation they tend to crack at the valve reliefs. Do the Cobb ceramic topped drymoly coated version of the JE (we sell them ).

If you don't plan to get engine management, then the 8.5:1 pistons are a must if you wanna look at more boost on pump gas. Also, you will want to o-ring the block while it is apart, to prevent blown head gaskets. The rods and crank and bearings should be fine under 10-12 psi, but get crower rods and arp bolts if available if you wanna run more than that. For over 400hp you will want to weld the cylinder sleeves to semi-close the deck, but to 10-12 psi I wouldn't bother. I would only knife edge the crank if I was running higher rpms than about 10% over stock or more.

But, that is just me...

Larry
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Old 07-08-2002, 08:34 AM   #16
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Quote:
Originally posted by GuerillaRacing
10.5:1 (or stock ratio) compression.
Does the MY02 OBS have a different EJ25 than other MY02 Imprezas?
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Old 07-08-2002, 11:34 AM   #17
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larry, please PM me more info on your pistons your selling.
Also do you guys have instructions on OIL squarters?
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Old 07-08-2002, 02:25 PM   #18
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Does anyone have any pictures of oil squirters, or side porting vs top porting exhaust?

Maybe some price guestimates on them also?

I am very curious too.

Thanks
-Eric
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Old 07-08-2002, 10:23 PM   #19
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Another vote for 8.5:1 C/R pistons. Number one reason is that the 8.5:1 pistons are off the shelf and will cost 650. The 9:1 pistons will need to be custom made and I'm guessing will cost more. This is all stuff I've read on here, so take this with a grain of salt. Please call JE and talk to them because I'm sure they will know a lot.

Pistons are the first thing I would replace simply because that is the peice that fails. Larry broke his, Hayscoob, and others. Rods will be ok, but while your in there you can if your budget allows to replace them. No need to work on the crank. Tighter valve springs will hold the boost without float. Other than that things will be ok for what you want.

-Chav
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Old 07-09-2002, 01:41 PM   #20
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Assumin this is a 2000 model car, the psitonm AND rod are both major weak points to making serious HP.

What si teh rest of this kit going to consist of? That will make deciding CR much easier, and might even give us the answer.

Whata re you doing about the block? At the very least it should be semi closed, at best, fully closed


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Old 07-12-2002, 02:17 AM   #21
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So, if the rebuilt/o-ringed shortblock that I stuck in my 2000 RS-T has a phase II block and phase I pistons/head gasket, then what kind of rods do you think I got?

i.e. do the phase I pistons require phase I rods?

The motor was originally in a 1999 Forester, and it had piston clearance problems with too thin a head gasket. So they took out the motor, gave them a new one, rebuilt this one, and I bought it for $700.
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Old 07-12-2002, 10:45 AM   #22
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pI pistons will fit in a pII block on the pII rods, however at TDC the pistons are extended past the deck .5-1mm. You can not put a pI rod on a pII crank due to journal size differences, from what I understand.

Larry - most likely you have a pII block with MY99 pII pistons (square indentation on the top, 2.5mm deep) and pII rods. pI pistons have 3.5mm deep square indentations on the top.

BTW, the benefits of ceramic coating - is it just to reflect more heat, basically? I don't think it actually strengthens it at all...? How much does the coating usually cost on top of the cost of pistons ($650 from JE)?
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Old 07-13-2002, 12:41 AM   #23
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I didn't measure the depth of the indentations, but the piston holds 15cc of fluid in the square dish. The pistons DID extend past the block which is why we used a very thick head gasket to make up the diff.

Which piston would that be?
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Old 07-13-2002, 12:58 AM   #24
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i got my 100mm 9:1 from JE for 650 to my door.


8C: what do you mean about MY99 pistons? i have a 2000 and the pistons i receieved from JE have a rectangle indentation.




also, i chose to do 9:1 because i honestly dont wnat to go crazy with the car. im looking to make a reliable 300-350hp. this is also why i didnt put in new rods as well. i dont wnat to go crazy. i know i will be happy with the 300-350 and i honestly dont think im ready for 400+hp. ill kill myself and probably someone else. not ready...not yet.


you can also stroke the engine. Paeco will do that for you for 1300. then add their rods and pay about 2100 or so for a fully done up engine.

Last edited by Andrew; 07-13-2002 at 01:05 AM.
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Old 07-13-2002, 01:38 AM   #25
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We're (8 and me) OT talking about stock pistons from older models in my phase II shortblock...
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