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Old 05-03-2004, 01:07 AM   #1
ChruiSSer
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Default Fully built 2.5L

I've got a couple of questions, but basically I'll start off with what I'd like to do and some inputs...
Once this motor takes a crap,(01 Rs 2.5L) I would like to bore it out as far as I can. Then build it up. From crankshaft to pistons, I'd like them to be capable of running a turbo possibly...I would get cams, heads, etc...I'm looking for the most hp out of the bored over block as possible, N/A. Also reliable...
Has anyone come across anything like this? I figure I would most likely need a new trans, but that's no big deal. If I recall is the largest it can be bored out to, a 2.9L? Depending on how my hp it'll produce then, I might also throw a small turbo on it, but for now I would love for it to be N/A...My motto is "There's No replacement fore displacement" so I would like to keep away from the Turbo's and Superchargers as much as I can... Also what would be the most HP i could get out of the block without boring it over at all? If anyone has any links or input that would be sweet. Thanks..I'll keep everyone updated as my search/project goes on...
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Old 05-03-2004, 02:34 AM   #2
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If you haven't checked it out already, www.rs25.com has lots more info.
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Old 05-03-2004, 08:38 AM   #3
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Default built 2.5

Unless you're looking for more than 270 hp, I'd check out techworkseng.com. I've been talking with Keith Croucher over there about a full motor build up, and they can get alot out of that motor with minimal boring (.020 over). One of the problems with going larger than that is flame propagation. The piston top would be so wide, that you'd have unburned fuel mixture around the outer edges of the piston. TWE does a fantastic job of squeezing as much out of the motor as possible, and with the right engine management and injectors, (and a new tranny) you should be able to kill WRX's and keep up with STI's. Remember, our cars weigh over 200lbs LESS than the new impreza, and going with an N/A build gives you more power across the entire rev band. Their fully built motor, running 11.2:1 CR, and stage II heads will run around $6500, if bought from them, not including shipping to/from canada, but xcelleration.com will sell you the same motor for around $1500 less, mostly saving you in labor. Contact Sam @ xcelleration.com for more info.
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Old 05-03-2004, 03:25 PM   #4
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*waits for dcoty to chime in*
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Old 05-03-2004, 09:11 PM   #5
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I will, but when i have enough time to write it all
Dan
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Old 05-04-2004, 04:21 AM   #6
Kevin Thomas
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Quote:
Originally posted by dcoty
I will, but when i have enough time to write it all
Dan
There you have it! Wise words from the immortal Dcoty himself.
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Old 05-04-2004, 02:50 PM   #7
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*bows down to dcoty*.
You really should put together a webpage about your car!
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Old 05-04-2004, 03:15 PM   #8
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I have a question about going that high of power. Will the open deck block bit the dust with that high of power? I know some people can take it up to about 250 hp with block upgrade. Is this even possible with a stock block and boring/stroking it out larger?
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Old 05-04-2004, 03:58 PM   #9
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Quote:
[i]My motto is "There's No replacement fore displacement" so I would like to keep away from the Turbo's and Superchargers as much as I can... [/b]

Its my understanding that the no replacement for displacement arguement is stating that generally the larger dispalcement has mor potential than an engine of smaller displacement (excluding engine type..e.g. rotary). I dont think turbo or supercharger has anything to do with this. In fact, I believe that supercharging or turbo will greatly improve horsepower gains no matter what the size. Throttle response will not be as great with boost, but you said that you were looking for the most horsepower. I believe you would get that out of boosting...and increasing literage to a certain point. MY point is that I think you misunder stand that phrase. Happy motoring.

Randy
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Old 05-04-2004, 06:01 PM   #10
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I don't think so: "There is no replacement for displacement" means that nothing you do to a small displacement engine will make it better than a larger displacement engine that is similarly modified; sure, you can turbo/nitrous/supercharge your 1.6L honda civic and make 400HP, but those same mods on a big block V8 will yield 1000horses.
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Old 05-04-2004, 06:24 PM   #11
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Quote:
Originally posted by powerlabs
I don't think so: "There is no replacement for displacement" means that nothing you do to a small displacement engine will make it better than a larger displacement engine that is similarly modified; sure, you can turbo/nitrous/supercharge your 1.6L honda civic and make 400HP, but those same mods on a big block V8 will yield 1000horses.

also stress per clyinder is mixed in with the phrase regarding displacement. for example F1 cars are about 3 liters (right?) and are v10 or v12 but have huge amounts of hp, N/A too i think.

to reiterate:
2.0l - wrx = 56 hp per clyinder
2.5l - 2.5RS = 41.25 hp per clyinder
4.6l - mustang GT = 32.5 hp per clyinder
5.7l - covrvett Z06 = 50.6 hp per clyinder

basically more displacement makes it so each cylinder goes through less stress to make more hp.

something to think about. sorry if im not very clear.
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Old 05-04-2004, 06:38 PM   #12
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Quote:
Originally posted by RS_to_WRX_swap
also stress per clyinder is mixed in with the phrase regarding displacement. for example F1 cars are about 3 liters (right?) and are v10 or v12 but have huge amounts of hp, N/A too i think.
.
Yup, but they also rev to ~15000 RPM.
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Old 05-04-2004, 11:11 PM   #13
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There is so much wrong with this thread. And I can't believe that it has gotten this far without some of the core members who are commenting bringing it to light.
Bored out to 2.9L I might want to throw a small turbo on it once I am done? I don't mean to flame, but these ideas show not only very little understanding of the EJ25, but little understanding of engines. There is no way in h3ll you can get an Ej25 to 2.9L. And you have to choose. Either you get a high CR NA build or a low CR turbo build. Sure, guys are doing RS-T's on stock compression, but they also can't run enough boost through them to make serious power safely. But that is for another forum.

Now, since this is the NA forum, I will talk about an NA build:

Get the heads ported and polished and built. Who does it doesn't really matter. Go with Cobb, go with TWE. They both provide quality product with similar springs and high performance cams. Please do not turn this into another Cobb vs. TWE thread. With that done, you will be able to rev to 7500-8000rpm.

Then get the bottom end done. Have the block blueprinted and balanced and put in some high compression pistons. Something in the low 11's if street driven, you can go as high as 12 if it will be track only. Again, who does it doesn't matter, as long as they build Subaru engines. Obviously you don't go to a chevy shop to build your EJ25. You can use your stock block and have it rebuilt. Personally, I am using an EJ257 block and getting custom pistons made to replace the low CR turbo pistons.

And then you will need to look at the intake manifold. At this point it will start to limit your performance. Dcoty is working on his own designs with his brother, and you can wait for his comments on that. Others are looking into cutting the new composite manifold to port it and putting it back together. Because of the bends in the spider legs of the manifold, you just can't P&P it. You will not be able to get to the narrowest section of the runners without this. Others are playing with Idividual Throttle Body designs. You really only need to address any of this if you must have more than 230Chp. If that is enough, then leave it stock.

The stock injectors are big enough for this kind of power. Just get a Walbro 255l fuel pump and a fuel pressure regulator to bump the stock pressure up a bit.

The stock ignition system should also be up to snuff. But some guys want the added power of an MSD igntion. Do it if you got the money, but don't worry if you can't. It is only a few horses, max.

And then you need engine management. On this, I recommend to use what your engine builder is familiar with. I guess that is my advice across the board. Find someone that you can do your build with. Someone that can be involved in the whole project from beginning to end. Since you are in Jersey, maybe give RalliSpec a call and get their thoughts...
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Old 05-05-2004, 10:50 AM   #14
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Quote:
Originally posted by powerlabs
I don't think so: "There is no replacement for displacement" means that nothing you do to a small displacement engine will make it better than a larger displacement engine that is similarly modified; sure, you can turbo/nitrous/supercharge your 1.6L honda civic and make 400HP, but those same mods on a big block V8 will yield 1000horses.
Homeskillit, you got to read my post...."Its my understanding that the no replacement for displacement argument is stating that generally the larger displacement has more potential than an engine of smaller displacement (excluding engine type..e.g. rotary)."....."I believe that supercharging or turbo will greatly improve horsepower gains no matter what the size."


Quote:
Originally posted by RS_to_WRX_swap
also stress per clyinder is mixed in with the phrase regarding displacement. for example F1 cars are about 3 liters (right?) and are v10 or v12 but have huge amounts of hp, N/A too i think.

to reiterate:
2.0l - wrx = 56 hp per clyinder
2.5l - 2.5RS = 41.25 hp per clyinder
4.6l - mustang GT = 32.5 hp per clyinder
5.7l - covrvett Z06 = 50.6 hp per clyinder

basically more displacement makes it so each cylinder goes through less stress to make more hp.

something to think about. sorry if im not very clear.
And yooooooouuuu.... j/k... Sure a 2.0 l WRX has more hp/L than a vette, but its turbocharged!! Turbo a vette, and see what happens.
http://forums.corvetteforum.com/zerothread?id=793784

Also the 2.5RS which is a H motor vs a vette OHV, vs a mustang SOHC (and not really Fords good NA motor ..5.0!!) I'm just not sure thats all a fair comparison. And yeah, why are you bringing F1 motors into this LOL.. thats like comparing apples to genetically modified apples.

All meant in good spirited debate...thanks for the conversation all!! Let the thread hijacking begin!!

Randy
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Old 05-05-2004, 01:56 PM   #15
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yeah sorry my statment was kinda out there. i was just picking cars that i know the hp. but if your going for displacement and what i said above ( more pistons = good) swapping in a H6 from a legacy might not be out of the question.
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Old 05-05-2004, 02:05 PM   #16
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Thats cool man,

And the legacy's a 3L taboot!! vroom vroom. I wonder what the new weight distribution would be with that motor?

Randy
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Old 05-06-2004, 04:13 AM   #17
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weight distabution is a good point. but it couldn't be to big of a diff.

are there people out there who offer build ups for the H6?

i have never heard anyone but me use the word "homeskillit" lol
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Old 05-06-2004, 05:19 AM   #18
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This thread is way off.. The 5.0 is Ford's good engine? lol.. I'll have to address this tomorrow when I'm not physically exhausted..
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Old 05-06-2004, 11:06 AM   #19
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Hey I said "FORDS" good NA motor!!

Randy
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Old 05-06-2004, 11:22 AM   #20
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We are getting *way* off topic here guys. This discussion is about SUBARU engines, not Ford or Corvettes!
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Old 05-07-2004, 08:03 PM   #21
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Hey everyone,

2.6 litres is about the max you can bore out a 2.5L, and you cant change the rod length either (i looked into doing this for my build).

Matt Monson pretty much mentioned everything i wanted to...if your going to do an N/A build, you should decide now since your compression and cams will be wayyyy off for any turbo application.

If your spinning your motor to 8k, then take it from my expreience and get an oil cooler and oil pump to prevent oil starvation to the two middle con rod bearings (and just to be on the safe side). Our block has 3 oil passages for the con rod bearings on the crank (one port for the far left bearing, one port for the far right bearing and one port for the two middle bearings...hence the failure of those two bearings on my car). An oil cooler is the easiest and cheapest way to avoid engine failure, along with an oil prssure/temp sensor to be on the safe side.

Fuel pump is a must for sure, but right now the stock fuel injectors are just shy of their max duty cycle under WOT, but im not sure how it will be with the new cams in my car now, it weill need some tuning for sure.

Matt is once again right about the intake manifold, its the weak link on my motor right now and it has to go! we are trying to build the manifls 9which is going smoothly) but we are a bit behind since my motor failed (but its back in an running, just need a new clutch).

I cant rattle off abnything else right now, but this is a good thread!
Dan

Last edited by dcoty; 05-09-2004 at 01:58 PM.
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Old 05-07-2004, 08:52 PM   #22
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Any ideas about turning a 2.5L V8 STI block into a high reving, bored out, and stroked n/a motor? what about using jdm heads and putting in n/a cams. that would be unique.
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Old 05-07-2004, 10:30 PM   #23
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Quote:
2.6 litres is about the max you can bore out a 2.5L, and you cant change the rod length either (i looked into doing this for my build).
Call Quirt at Crawford. I misplaced his number and email address, but you can get that from I-speed.

He will enlighten you.

cheeRS,

Greg
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Old 05-07-2004, 10:33 PM   #24
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I think it would be a waste of money. You are going to spend $6000+ on the engine and then tear it all apart and put it back together with NA parts that will cost you another $2-3000. Sure, you couls sell a few of the parts, but it seems like a lot of extra work...

The only reason I am considering using an Ej257 shortblock is it is cost effective. The block costs $1500. High CR pistons will be +/-750 and I can likely sell the stock pistons for $400 to someone building an RS-T. When you compare this to a Cobb built or TWE built EJ254 block, it saves you $1000-2000. Most guys doing NA EJ25 builds are spending $8000-10000 on their engine. With an EJ257 shortblock and Cobb heads I will be spending more in the neighborhood of $6000 on my engine. Basically, no matter how you do it, it will cost you a lot and it will cost more than a turbo engine swap...
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Old 05-08-2004, 02:44 PM   #25
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Ff course it would be a waste. and just about every person on these boards that says they are planning doing an all motor build up never carry through. but its still fun to dream about. i but it would be one hell of an autox car.


back on track....would there be any benifit from a semi-closed deck block for super high compression? or is the head gasket the weak point?
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