So, since nobody can tell me to go search the threads (there are none) can anyone tell me if there's a chance in heck of making 200 bhp without serious A/F and spark control and/or cams? I am not opposed to either, in fact they are in plans, but I'm broke and have to pace myself. What can I reasonably expect with simpler bolt-ons? I have already decided on Borla headers, Stromung SS dual tip, Cobb intake and maybe a Random Tech cat, but that's in between the much more important suspension tweeks. Just looking to see if any of you fellas have already been down my path.:)

2 words; probably not.

You'll be lucky to get 15-20HP from basic boltons (intake,header,exhaust, pulleys). The main limitation of the EJ25 is heads & cams that weren't designed with high-revving horsepower in mind. Your engine was made for low- to mid-range grunt, and also decent mileage. 200HP is possible with heads, cams, free-flow cat, and boltons.


Borla headers don't make much HP, there's a british company (PDE? I think) that makes a 4-into-1 design that's supposed to be good. Also, it's rumored cobb will make their own headers eventually. I like the looks of MRT headers, seems like a good design.

Borla's sound nice though...

But you really aren't gonna make much progress without headwork & cams, unless you go forced induction.

I say spend the money on tires, harnesses, seats, and maybe lightweight stuff (hood, bumper beams). If you want more power, save for the good stuff, dont' just make your car noisier.

-scott-

Thanks, Scotty.

That said, do the, say, Cobb heads cut into low end power then?

I orignally started out for the N/A build up but moved onto the RS-T since I got a deal on the turbo kit from Shiv. Yep the SCC project white 2.5RS's turbo kit is sitting in my car now.

Originally posted by N/A
I orignally started out for the N/A build up but moved onto the RS-T since I got a deal on the turbo kit from Shiv. Yep the SCC project white 2.5RS's turbo kit is sitting in my car now.

That is exactly my inspiration for future plans. Any more power than Shiv made just costs you gears every couple months. Any less and you aren't beating a WRX dollar-for-dollar. SCC is also the biggest reason I came to 'feel the force' rather than joining the Honda darkside- I was considering an Si when I bought the August 2000 Eight Great rides issue. All Suby, all the time since then. DC and Jacquot rock. I planned to build me up a rally beater, but the car I got for it was a 1980 280ZX, and I just can't bring myself to destroy such a sweet car. So, when I can justify having a third car I'm going to get an Escort or something similar that I will enjoy thrashing. :D

maybe u can make it sound like 200 hp :D

I got mine up to 140 whp and 144 trq with just a intake, brullen header, stromung exhaust, zex plugs, and s-afc.
Got close to 200 with 180 whp and 202 trq with 55 shot of zex nitrous. Was thinkning of going up to 75 just to see.

I also have a dual over head cam system that came with the 98's only

That said, do the, say, Cobb heads cut into low end power then?

I think that the Cobb heads are designed for top end power. This is why they reccomend raising the red line, because the stock redline is right where it is making power.

-Wes

Originally posted by RebelINS
I think that the Cobb heads are designed for top end power. This is why they reccomend raising the red line, because the stock redline is right where it is making power.

-Wes

Actually, bone stock EJ25's have a pretty severe power falloff above 5500 rpm or so. Shifting higher than that is supposedly slower, but not as much fun. And I have heard some clips of N/AEJ25's with those mods.... they sound SWEET.

I think you are misunderstanding what I am saying. Cobb redesigns the heads so they flow better. By doing this, along with a few other mods, it moves the curve up, which makes the stock redline inadequate. You are correct about in stock form there is a power fall off.

-Wes

yeah, I forgot to delete the part yyou said about the Cobb heads. They are good, but for that kind of money I'd probably jump straight to forced induction and/or a new car.

do a search

haha j/p, i have a cobb, stromung catback, and had borlas. it is very nice. i like the setup. you won't be disappointed...however imselling the borlas and getting MRT headers/cat, coatin them, and will prob get better perf. out of them since i dun care about CEL no more since i already have one =P

I think that you can get up to 250 at the crank if we could get a redesigned intake manifold, with an intake, headerback, cams, heads, Engine Management, Phenolic Spacers, Pulleys, improved spark, Walbro, parallel fuel rails, And a redesigned Air Box.

Originally posted by N/ABeast
I think that you can get up to 250 at the crank if we could get a redesigned intake manifold, with an intake, headerback, cams, heads, Engine Management, Phenolic Spacers, Pulleys, improved spark, Walbro, parallel fuel rails, And a redesigned Air Box.

Uh huh. Do I get fries with that?

Originally posted by N/ABeast
I think that you can get up to 250 at the crank if we could get a redesigned intake manifold, with an intake, headerback, cams, heads, Engine Management, Phenolic Spacers, Pulleys, improved spark, Walbro, parallel fuel rails, And a redesigned Air Box.
For 250, I would shoot for independent trottle bodies and a design like that 270hp 2.0l N/A engine in that race car Impreza in Japan... With the 2.5, I bet it would break 300hp in a simular configuration.

Blah. Now we're talking severe law of diminishing returns. For that kind of money you could have a 10 second or better turbo car. I'm not gung-ho enough on N/A to do it just because.

Originally posted by BAN SUVS
Blah. Now we're talking severe law of diminishing returns. For that kind of money you could have a 10 second or better turbo car. I'm not gung-ho enough on N/A to do it just because.
And this is not the turbo forum :p Its about N/A power limits!!!

Diminished returns my ass, have you drivin a high 200hp N/A 4-cylinder Impreza? Nooooooooooooo... Not many people have either, but the low 200hp N/A cars are nasty as it is. :p

And we all know that going that fast in a Turbo car causes ALOT of maintenance problems, like exploding tranny's, blocks, and all sorts of stuff... With that much money into a high power N/A engine, it would stay much more reliable ;)

reliable, shmeliabel. I wanna go FAST! Haha, just kidding, that's why the turbo kit comes after I crack the 200 hp barrier with a PEMS. I want to be able to tune well before I add boost, and even then I won't get crazy. Plan on using a small, fast-spooling kit limited to about 250-260. In between I might use nitrous too, but I doubt it since I'm not a big drag fan and it's not wise to keep on the street. One thing at a time. Maybe by the end of next year I will add cams. Everything I've read and heard about the EJ25 points to them as being the biggest obstacle to better power.

Here you go, the nastiest N/A Subaru I know of:

http://www.spomotorsports.com/images/PhotoGallery/car2.jpg

http://www.spomotorsports.com/images/PhotoGallery/car3.jpg

http://www.spomotorsports.com/images/PhotoGallery/engine6.jpg

On the web site it says 360hp or 300psi though, Ive seen a JDM magazine with the same car but showing only 270 or so, i'm not sure anymore...

http://www.spomotorsports.com/PhotoGallery2.cfm?CustomerID=#CustomerID

http://www.syms.co.jp/pages/history.html

To be honest, I am simply unimpressed with such a high-strung, all-out motor. The 600+ hp FWD turbo drag cars don't do anything for me either. Speed costs money, and all those cars prove to me is that someone has more than me. A 250hp RS-T homebrew RS-T is what gets me going.

I do appreciate, however, that when factory-backed teams dump 6 figures into a race car for a season, it filters down to us on the street, resulting in my 2.5l flat 4 getting me down the quarter faster than 5 and 6 liter muscle cars from the 60's and 70's.

Why are you talking about drag racing??? I'm not...

Originally posted by Kostamojen
Why are you talking about drag racing??? I'm not...

Just referencing the fact that pure race/strip cars can make much higher peak outputs than 'street' cars. I don't expect driveability to stay the same in a 250-300hp N/A EJ25. I imagine it would be a lot like driving a Honda, only faster, haha. And I wasn't quoting. Also, I post here because I have a N/A car, but it will probably eventually be turbo... but that doesn't mean I should post there. Basically I'm just expressing my opinion, not meaning to step on toes. I yam what I yam and that's all that I yam. Plus, when I originally started the thread, I asked what I could expect out of 'basic' mods. I consider anything past replacing the cams to be beyond 'basic.' Even that is pretty involved.

How about shoe horning in a H6 3.0L motor and building that up? Maybe some 12 to 1 compression pistons like the V8 guys? The four throttle body setup works great on any car. The GTI-R Nissan built used them to add to the low end response and it worked great. Of course they also used two springs per valve, a distributor system and it was a turbo motor. Oh the intake manifold was a very clean design as well. From the intake it was a direct line into the cylinders for the intake. The exhaust only made a slight bend before entering the exhaust manifold.

Originally posted by N/A
How about shoe horning in a H6 3.0L motor and building that up? Maybe some 12 to 1 compression pistons like the V8 guys? The four throttle body setup works great on any car. The GTI-R Nissan built used them to add to the low end response and it worked great. Of course they also used two springs per valve, a distributor system and it was a turbo motor. Oh the intake manifold was a very clean design as well. From the intake it was a direct line into the cylinders for the intake. The exhaust only made a slight bend before entering the exhaust manifold.

Sounds like fun. I'd like to try that in a 1.8l OBS...

"Borla headers don't make much HP, there's a british company (PDE? I think) that makes a 4-into-1 design that's supposed to be good. "

Do you mean TWE (Tech Works Engineering) based out of Calgary, Canada? They have a 4-1 merge collector header. Apparently very few out there since they are going through some issues to get setup to do ceramic coating.

Yeah, that's them, TWE. I thought they were overseas, but that's good that they're closer. Has anyone got dyno charts from their headers? I would think that headers should make a difference on our cars, the stock ones seem like quite a comprimise. I'd like to see something that moves the placement of the cat converter, maybe removes it, and has the manifold making less twists & turns.

-s-

Originally posted by BAN SUVS
How about shoe horning in a H6 3.0L motor and building that up? Maybe some 12 to 1 compression pistons like the V8 guys? The four throttle body setup works great on any car. The GTI-R Nissan built used them to add to the low end response and it worked great. Of course they also used two springs per valve, a distributor system and it was a turbo motor. Oh the intake manifold was a very clean design as well. From the intake it was a direct line into the cylinders for the intake. The exhaust only made a slight bend before entering the exhaust manifold.
I would try that, but only for a drag car... it would totally fuxor up the weight differential of the car... make it like 60/40 or worse.

Originally posted by Kostamojen
I would try that, but only for a drag car... it would totally fuxor up the weight differential of the car... make it like 60/40 or worse.

I don't think 25-30 pounds that would come from a turbo/intercooler kit would tip the scales that far. What exactly did you mean?

EDIT: You mean the OBS swap thing?

Originally posted by BAN SUVS
I don't think 25-30 pounds that would come from a turbo/intercooler kit would tip the scales that far. What exactly did you mean?

EDIT: You mean the OBS swap thing?
Whoops! Quoted the wrong post!

And a turbo/intercooler with all the piping and equipment is a big more than just an 30lbs... Unless you got some really lightweight exhaust piping... (Note the WRX's 100lbs weight difference to the concurent model RS's)

Originally posted by Kostamojen
Whoops! Quoted the wrong post!

And a turbo/intercooler with all the piping and equipment is a big more than just an 30lbs... Unless you got some really lightweight exhaust piping... (Note the WRX's 100lbs weight difference to the concurent model RS's)

Yeah, I got thinking about that after I posted and realized just the turbo could weigh close to that much. Just didn't feel like editing. Since I wouldn't get any whore points, hahaha.

So back to my comment about raising the compression from its 10 to 1 up to as much as 12 to 1. Has anybody tried it yet? It might not give the big hp gains but I'd imagine it would help out to give the car even more of the low end torque that makes the EJ25 so fun.

I am also interested in what the higher CR pistons will do for our car.

Has anyone seen the SYMS prototype Intake Manifold, it looks pretty damn sweet..

Just to add to the fire, to get 200 bhp cams and heads.

I would recomned Cobb's N/A settup..

If your on a budget like I was best way to get parts are from message boards... I got mine from the old I-club for a very good price... but like some people have already said, simple bolt-on's won't get you to your goal... you'll need the engine interals.

On the otherside I was quite happy with my purchase:
3rd gen Borla headers
Stromnung 76mm cat-back w/ SS Dual tip Muffler
UD Pulley
K&N with Larry Ganza's Pipe

My best time was a 15.01 on the 1/4 with a trap speed of 89.88 mph this was a cool night in October and had stock suppention and tires. Running on 91 octane.

With my setup there is barely and lost in low-end. The mid-range is increased and the high-end is incressed... actually it seems that the higher I go the more it wants to go... what I mean is if I have it in 4th going 70mph the rpms are aroung 4500. I slam the pedel it shoots from 4500 to 6250 in seconds w/o hessatation.

Personally, this setup is great for auto-x, nice tight ones.

There are tons of products out there but if your on a budget there's no point in payin full price if someone else is willing to sell their stuff. Plus, all the parts out there are already test proven eg the borla, stromnung... so if you don't want to waste your money or time going through parts. try looking for someone who's interisted in selling their parts....

Well the internals will help if you raise the redline, but our cars are lacking air IMHO. We need more airflow so we can add more gas and spark :) I don't think upping the compression will do much, but why not do it if you're building the engine anyway?

Youre right about finding used parts. I recommend CObb parts too, I just don't recommend their prices..

I lay awake at night, dreaming of Cobb Stage 3.

But $4,000 is a hefty price tag, and everything I touch mechanically turns to salvage, so I'd have to pay professional mechanic to install and tune.

My fear of purchasing internals used is that I wouldn't know how well they were treated, and I wouldn't have confidence in their reliability.

http://www.rs25.com/forums/showthread.php?threadid=5644&goto=newpost

Check it out... your dream come true

Originally posted by Deznuts05
http://www.rs25.com/forums/showthread.php?threadid=5644&goto=newpost

Check it out... your dream come true

Thanks, but I need Borla for '02 ;)

But you're right, I just need to keep looking through FS's

The 01 should go right on the 02. It's the same engine. Just that there is a different place for one of the exhuast hangers.

reaaaaaallllllyyyyy.....maybe I need to chat with the wifey about loaning a poor guy $200 :D

Save for MRT, you wont be disappointed.

MRT Header?

The MRT headerback yields 14HP gains.

two things,


1. The improvement in torque should be about equvalent to the improvement in BMEP which is the ratio of new CR divided by old CR - result taken to the 0.4 power

Example - if you had 10:1 and now have 10.1:1 (10.1/10.0) to 0.4 power is 1.00398
OR 100 ft lb -> to 100.398.

2. The 2000 RS has almost 11:1 compression...

I can't verify either of these items but they are interesting to note.

I thought the highest was a 10 to 1 compression? 11 to 1 sounds damn high already. Maybe then Tony Rigoli builds a 2.7L conversion kit for a non-turbo application. 2.7L's and 12 to 1 compression. Hell might as well do the H6 3.0L idea I mentioned earlier.

I would how reliable a high stung engine like these would be. IMO not very. But hey, what the hell......:D

-scu

It would be hell of alot more reliable than a turbo. These are some of the things I have done/will do to my car.

Cobb Intake
Cobb Heads/Mild Cams
Custom Intake Manifold/TB
MRT Exhaust
N1 Pulleys
Apexi S-AFC
Proecm Chip
Phenolic Spacers
Walbro Fuel Pump
Some type of Upgraded Spark
Exedy Clutch and Flywheel

How unreliable does that sound? IMHO it sounds as reliable as stock..

I have Cobb Stage 1 heads, Street cams, an Injen intake, MRT full exhaust, and an S-AFC. All together the car has put down about 37.5hp over stock at the wheels on an AWD dyno. So, I figure I'm in the 205hp ballpark at the crank.

The car feels like it's lost some low end as a result of all of the modifications, but on the dyno the graphs show that it's up on torque even at 2500rpm. I think it feels slower because the top end is so much better, if that makes any sense.

I think there's quite a bit more power to be had with an aftermarket ECM of some sort. As it is now it seems like the stock ECU is pretty confused - throttle tip-in at lower RPMs is sometimes less than smooth, the idle can be a bit jumpy, AFR is not ideal (even with the S-AFC), I'm sure timing isn't optimum, etc.

Oh, with the Stage 1 Cobb stuff the redline does not need to be raised to get the full benefit. The Stage 2/Club Racer combo is what works best with a higher redline.

Pat Olsen
'97 Legacy 2.5GT sedan

Cams are easy. Time consuming, but easy. In fact I just installed them today. I need to double check my valve lash (I may have forgot to do #4) because it's clackin' pretty bad. Even with the clacking, it sounds stronger and OH SO GOOD!

It's parked until I can fix it.

I'm pretty confident I'll be pushing over 200hp now.

adjusted the valves.
The cars power is sooo smooth. The ECU is still learning (I reset it). It has only run for about 40 min on the new cams, but it runs great. I think my O2 sensor might be going out because the car is running a little rich, but that could be the ECU learning as well.

Anyway, I don't know what kind of power difference there is right now. I've been driving easy to give the cams some more break in time and the ECU time to learn. BUt I can tell you that it is so SMOOTH and fluid. The hesitations around 4kRPM isn't there.

Since we are on the topic, does anyone have anyclue as to how many HP (roughly of course) a full header back sys. and cams would yield ? and would there be any emissions issues ? I have heard of people failing. Right now my future plans look like this :

TWE Exhaust sys. & Cams , Hyper(whatever the hell) ground wires, intake and ECU tuning. After this a nitrous setup with progressive controller.


While am it, What kind of maintenance is required with cams ?

Thanks for hearing all my crap LOL. P.S. am not looking to break speed records just hold my own :)

from COBB: Dyno testing, comparing a stock 2.5L with and without camshafts, has shown a +14 PEAK HP GAIN to the wheels and +13 ft-lbs PEAK TORQUE GAIN, with maximum gains of +19 HP at redline!! These gains were seen when comparing otherwise unmodified, stock cars. More gains are possible if your vehicle is modified with upgraded intake and exhaust systems

I think the key is MORE GAINS are possible if you have a modified intake and exhaust. These cams will like the headers and an intake. Cams like this increase the volume of air going through the engine. If the stock engine benefits from freeing up the intake and exhaust because it is so choked, imagine how choked the engine will become with cams trying to increase the flow. I believe, and I could be wrong, that the headers would add more power to a car with cams than a car without cams. Of course, without dyno runs to prove this, my theory could be pure crap.

I do, however, have COBB cams and Borla headers. I'll let you know what kind of improvements I have after the break in time. I'll go run the 1/4 next week.

also from cobb regarding their stage three kit:
Many customers have enjoyed this reliable system for several years. Those that have taken their RS to the drag strip have typically run low 14's in the 1/4 mile

Well, my theory is that in order to produce more power with the EJ25, we have to have enough airflow to increase spark, increase fuel pressure, and produce power.. The stock intake manifold and throttle body suck. If we could have a setup like this; COBB CAI-> ITB->Custom Manifold->Cobb Heads->Cobb Cams->Built Block->MRT Headerback, we would have serious gains with a S-AFC or something equivalent.

Originally posted by N/ABeast
Well, my theory is that in order to produce more power with the EJ25, we have to have enough airflow to increase spark, increase fuel pressure, and produce power.. The stock intake manifold and throttle body suck. If we could have a setup like this; COBB CAI-> ITB->Custom Manifold->Cobb Heads->Cobb Cams->Built Block->MRT Headerback, we would have serious gains with a S-AFC or something equivalent.
I think a full on aftermarket ECU would be better than just an S-AFC.

Sometimes I wonder if it would have been more fun driving an N/A beast (230-250hp to the crank) vs a turbo'd sleeper (300hp or so to the crank). I mean, the money spent on N/A is probably at least the same, if not more compared to the higher output turbo setup. Sure, the car would last longer compared to the turbo, but you really aren't getting all that much gain for the money, and lots of labour both ways. Somehow to me, a Subaru is meant to be turbo'd even though the EJ25 might not be. Who knows - maybe I will go N/A after thinking turbo for a few years, just to save the wear and tear, even though I might spend even more with N/A setup.

Well, N/A engines have no turbo lag, and if you can eventually get to 250 HP, you would probably be pleased.

Not to mention a high powered N/A configuration would maintain a better weight ballance and with the 2.5, a sheep load of torque without turbo lag to worry about...

You can also gut your car and have a lightweight, N/A Impreza that eats many cars for breakfast like I plan on doing!

Originally posted by N/ABeast
You can also gut your car and have a lightweight, N/A Impreza that eats many cars for breakfast like I plan on doing!
That would be me as well if I had mucho dinero :p

Ok, there is something you guys are missing.
A high compression N/A motor with big cams and all that will give great power. But if you add any type of FI stuff (turbo or blower) You will get more. You might get turbo lag, but it's all relative. Text book turbo lag is on 8:1 compression cars that need the turbo to create any power. On a high compression turbo motor, sure there will be turbo lag, but you're lagging up to 400HP, instead of no lag to a whoppin 300HP.

See the difference?

Also, an N/A motor with big cams and High compression will have it's own lag and major loss of low end power when you go with bigger cams. Good Torque and throttle response are the product of a strong fuel signal. This is created by having high intake charge velocity. A 300HP N/A 2.5L engine WILL NOT have a high intake velocity at low RPM because the intake will have had to be ported out to a larger diameter to support the flow required for 300HP.
Larger ports=lower velocity= poor torque and throttle response<2k RPM
Stock size ports=higher velocity=good torque and throttle response<4k RPM
Sorry guys, but your dream (N/A) motor DOES NOT EXIST without running 13:1 compression and race gas.

The closest you'll get will be a high compression, SUPERCHARGED 2.5 with COBB ported heads, Equal length headers and a 2.5" exhaust.

Lastly, a N/A 2.5L will never have a higher power potential than a F/I 2.5L.

period.

Well, I'm sure we know there is a limit of what can be done with 2.5L of displacement - it's the reliability factor that's up in the air. An N/A beast making 250hp to the crank is probably just the same in terms of reliability as a turbo EJ25 making 280hp to the crank (very low boost needed), and I'm sure I would spend a heck a lot more for 250hp to the crank with an N/A setup. I'm not sure you will be able to keep at least the same amount of torque in the low end though... sure with N/A it's nice and natural (because there is no variable valve timing), but I ponder about the loss of torque as you go for the 250hp to the crank. And no, this is my street car so I don't think I will strip it down.

Well, I'm not thinking of getting a radical grind of cam. I'll probably go with Cobb Mild Cams, Get a Link ECU to tune well, have a custom Intake Manifold and TB made, along with a Cobb Shortblock and Heads. I think this will put you close to 250 HP..

And the cost of parts and labour for these?

About 7000

Originally posted by ImprezaRSX

See the difference?

Would you just stop already!!!

Yes, we all KNOW how much more power turbo charging and supercharging gives, but that is NOT THE POINT!!! NOW STOP!!! :mad:

I'm also debating if its feasible or not anymore. I mean, for $4000, you can buy the AVO Turbokit..

Originally posted by Kostamojen
Would you just stop already!!!

Yes, we all KNOW how much more power turbo charging and supercharging gives, but that is NOT THE POINT!!! NOW STOP!!! :mad:

No.

Fact is people keep speculating about what can and can't be done. I'm just saying that people think you can get a drivable 280HP+ out of the 2.5 Naturally Aspirated.

This thread is N/A EJ25 Power Limits.

So I stated that you CANNOT get those power numbers N/A Like so many people are fantasizing about without race gas and high compression. AND Even if you COULD get those numbers N/A you would have a car with NO low end and it wouldn't be very drivable. You could have a drag RS but that's it.

I was also stating that many of the uninformed people are using Turbo lag as their #1 reason for not going F/I. And that on a properly tuned engine turbo lag would be almost unoticable, the car would be drivable AND you could get the power numbers WE all crave.

So to sum this thread up:
300HP N/A.... reachable, but drag only and not streetable
250HP N/A.... sure, but you're going to need more than I'll probably go with Cobb Mild Cams, Get a Link ECU to tune well, have a custom Intake Manifold and TB made, along with a Cobb Shortblock and Heads. I think this will put you close to 250 HP.. because if you read cobb's site, you just squeek by 200HP with their Stage 1 Heads, Mild Cams, Headers, high flow cat, exhaust, underdrive pulley, CAI. IF you're going to stay N/A the spicey cams will be a must for those HP numbers.

and that's it.

Of course, you could add nitrous.

But, Im sure if you buy the cobb shortblock, heads, cams, Get a redesigned Intake Manifold, ITBs or a bored TB, and all the usual bolt on goodies and tune it well, It will be around 250 HP without sacrificing driveability due to a radical cam profile.. Who talked about using wild cams to achive Honda like HP with Hondaesque torque? I'm certainly not.. I would just like the benefits of the EJ25 without the negatives such as its total lack of high end..

MAN, this thread wandered off on its own little tangent...

I posted this out of curiosity of what would happen if I did the upgrades to my car with the INTENTIONS of going F/I with a turbo setup like the old Minnam/Vishnu kits, but hadn't quite reached it. In other words, all the things I would do on a "normal" budget (think college student, but gainfully employed, with no rush) up to but not including the actual turbo kit. Which means, at most, intake, exhaust, headers, Cobb street cams, possibly a high flow cat and maybe fuel pump and/or return line mod. That's about it, other than maybe getting a tecIII before the turbo kit too. ImprezaRSX hit it on the head. Whether you guys want to believe it or not, a 4 cylinder car making 270+ hp at 6000 RPM and 105 ft/lbs at 2000 RPM is not very streetable. And yeah, Nitrous would work, but it's debatable whether or not one could call a juiced motor "normally aspirated."

Where was I? Oh yeah. Who cares how much horsepower a $7,000 dollar N/A motor would make, when it can't touch the peak power or drivability of $4,500 worth of bolt-ons and turbo. The only justification for pursuing that is just because you have the resources to waste and really want to see just what a N/A EJ25 can possibly do on a drag strip. What I believe we can achieve, relatively cheaply, is a N/A EJ25 that is the equal of pretty much any other N/A 4 cylinder car we would come across on the street.

Umm.. Ok.. A stock N/A EJ25 will kill almost any other stock 4 cyl on the road.. If you give me 7000, and you can spend an equal amount on a turbo kit, I can almost guarantee that you will not catch up to me once I launch a 2500 lb Impreza..

The problem I see is that not many parts are re-usable between a N/A setup vs Turbo setup (power-wise). CAI? gone. Exhaust? Bigger piping needed. Headers? Maybe, if you get the really good ones that won't crack when you slap a turbo behind it. Cams? Definitely different. Port and Polish? Lots of labour and you won't see much difference till you mod the car to hell, N/A or Turbo. You can address fuel and engine management, but those net minimal gains without other power mods and at a much higher entry cost.

Anything to increase power, you basically have to decide right up front whether you to go full N/A or Turbo - nothing really in between. As for going N/A, if you pick your parts well, you might not lose any torque down low, but you certainly don't gain much down there either - most of the power gains will be up high. Now as you tune for more HP, the torque curve will become steeper, making the car not as street friendly as before.

Now if you're going to strip the car down to the bare minimum, then sure, you don't need that much power because you're improving the power-to-weight ratio mostly by weight reduction first. However, the car will become a dedicated track car, not a daily driver.

Personally, I want around 250hp to the crank, preferably 300hp. When you need that kind of power figure, I doubt the reliability will be all that much different, and in a sense, the turbo might be cheaper to do. Someone PLEASE prove me wrong, and that a 250hp N/A beast will be street friendly, and doesn't cost more than a turbo setup producing the same power figure if not more.

DUDE, ALEX! You know I'm on this board. I'm member number 3. HOW DARE YOU put a 5000 word limit on a post! :)

Part 1.

Hello,

1. Horsepower is a function of the mean (average) pressure being exerted against the pistons in the cylinders.

2. A motor blowing up is a function of the peak (maximum) pressure exerted against the pistons in the cylinders.

2a. On certain Subaru engines, the head gaskets go before the cylinders (woah, novel concept, eh?;))

2b. Tuning determines peak cylinder pressure v mean cylinder pressure. Simple example: ignition timing is usually measured in degrees of crank rotation before the piston reaches the top of its stroke, on the way up toward the heads, when the spark plug fires. Too much advance and the flame front will propagate toward the piston and try to prevent it from reaching the top. If the flame front / expanding gasses push too hard, they crush the ring lands and pop the motor.

2c. Although not true in practice (timing of a single-point spark is not a good enough system), in theory you could continue to build power until you had many times more power than stock without ever changing peak cylinder pressure.

3. The engine doesn't care what creates the cylinder pressure (ignoring tuning-related pressure issues).

3a. Turbos and Superchargers force more air into the engine. The engine sensors (MAF and/or MAP depending on which Subaru we're talking about) detect the extra air and add appropriate fuel.

3b. More efficient NA engines draw more air into the engine. The engine sensors (MAF and/or MAP depending on which Subaru we're talking about) detect the extra air and add appropriate fuel.

So that's the story - it doesn't matter what setup you run, power is power. If you assume the tuning is the same (ie, both NA and FI systems are well tuned), then you can practically assume that peak cylinder pressures are the same and the reliability of both systems is the same, for a given power output. Two 230 hp cars, one NA and one FI, all else being equal, will be equally reliable internally.

Of course, once you get to higher outputs from NA motors, you typically need higher RPMs, which introduce a new unreliability factor...

PART II coming...

Joel

Dang lag. The forum is a 5:1 compression 2 liter motor with a big rig turbo on it. laaaaaaag. By the time I got over the 5k word limit, someone made some of my points...

Hello,

Part 2

4. Relative volumetric efficiency is a measurement of the amount of air entering the engine compared to the total volume of the engine.

4a. Ignoring super-high dollar NA engine design, NA engines in theory can peak at 100% VE, meaning the 2.5 liter engine draws 2.5 liters of air every two strokes. To get there requires very specific parts designed to operate at peak efficiency. Designers must chose a specific RPM range at which to reach that peak efficiency, because a part designed to be efficient at one engine speed will not be as efficient at another speed.

4b. Superchargers and Turbochargers can create a relative VE of well over 100%. A 2 liter motor running 14.7 pounds of boost at peak efficiency could in theory draw 4 liters of air every two strokes (200% rVE). Even at 50% VE, the relative VE of that system, compared to an NA system, will be 100%.

This explains why it's so easy for turbo motors to make more power than NA motors. Notice that a WRX makes more torque than a 2.5 by 2000 RPM. (or maybe earlier, even?) Sure, the 2.5 is a "torquey" motor, but its peak is way below that of the 2.0 turbo.

As for tranny-killing, that seems to be a function FIRST and FOREMOST of the driver. Then it seems to be torque related. A 2.5 turbo has far more torque than any 2.5 NA motor (street cars, obviously ignoring mega-0buck purpose built race motors. And this is because of the much higher VE even at low RPMs). A high powered 2.5 turbo makes far more torque than an even more powerful 2.0 turbo.

And since the first poster was asking about NA power as a prelude to turbo power, don't forget the part above where NA parts have to be designed with specific RPM ranges in mind. A good example is Cobb's "wild" or "spicy" or whatever he calls those cams. They have a large amount of overlap to help with scavenging, fully replacing the gas in the cylinders, etc. These things are important to improve VE at high rpms. These things "waste" some VE to gain overall VE. You loose some good intake charge in order to get a nice full cylinder. Well, add a turbo to the system and when the valves first open up, there's boost sitting right there. And it flows right through the engine and out the other side. The overlap will cause a HUGE loss in VE for a boosted car.

Now, note that a welcome fact comes from emissions laws. Emissions laws require cars to have very little cam overlap at the low RPMs tested. That makes for clean burning. In cars that don't have some VTEC mechanism (which simply introduces a higher overlap cam profile at higher rpms), there is only one cam profile - a low overlap profile. Perfect for forced induction. Emissions cams are great cams for FI.

Anyway, the cam example is an extreme example, but if the NA parts you are considering are well designed for NA use, they can detrimentally affect your future FI use.

Oh and lastly, N/ABeast, your comment on spending $7k on an NA 2500 pound Impreza versus $7k on a heavier turbo Impreza (on which car were you meaning?)... for what purpose? Street racing / drag racing? I'd take you up on that any day if that's the case.
How many 10 second non turbo Imprezas are there?
How many 11 second non turbo Imprezas are there?
How many 12 second non turbo Imprezas are there?
How many 13 second non turbo Imprezas are there?
Spend $1k on a WRX and you have a 13 second car (Vishnu Stage 0). Spend a couple grand more and you're in the 12 second range. Shoot, spend $7k on your Impreza and you can almost pay i-Speed to drop a bone stock WRX motor into your Impreza and you can run 13s. Put a turbo kit and a TEC-III into your Impreza for about $7k and you can run 12s and 13s, too.

Joel

Thanks Joel.
I tried to answer BAN SUVS question, but this thread turned into a hijacked fantasy thread.

Hey BAN, I talked to Tom at Ludespeed. He said his stage III kit runs GREAT on COBB Cams (street/mild) and Borla Headers. If you support the Turbo with something other than the headers you shouldn't have any cracking problems.

Until then, N/A, You'll get about 45HP with Cobb Heads/Cams, Headers, CAI, exhaust. When you change over, the CAI has to go and the turbo back exhaust should be AT LEAST 2.5" (3" is optimal)

Other than that.... I didn't get cobb heads, just the cams and I love 'em. IF you ever come to Hawaii look me up and I'll give you a ride.

Yep, I read the tech page on Cobb, and decided to eventually do cams based on their better performance with turbos. Before that I hadn't really planned on ever doing anything but pure bolt-ons. And, since Minnam seems to have fallen off the face of the earth since the SCC project car and Vishnu appears to be a WRX-only shop now, I plan on going with the Ludespeed kit. Eventually, considering the cost of a converting my '01 GM6 to a 12-13 second EJ25 is approximately equal to the down payment my lender told me I need to get a house. In the meantime, $2000 spread out over several months will make for a nice N/A street car that will hold its own on an autocross course.

Thanks for the replies guys, my questions have pretty much been answered. Actually, most of it verified what I had already figured out or been told and chose to believe.

EDIT: Oh yeah, I forgot, I'm not doing the heads at any point. Not nearly enough returns for the money considering I won't be doing any real competitive racing. So, I figure maybe 30-35 hp from the other stuff- which will put me right on the threshold of 200, right where I'd like to be.

maybe one day someone will have the balls to build something like what you guys are talking about.

on a side note though... My friend just dyno'd his E36 with cams, full exhaust, chip(forgot make) and he put down 350 whp. I'll see if i can get a copy to post.

Isn't that a 6 cylinder though with higher displacement? What's the stock power figures on that engine? percentage wise, pushing our motors to 250hp at the crank is a good 50% increase, and doing it in N/A can be kind of freaky...

That's about 50% for the Bimmer 3.0 I6 too. Sweetest motor on the planet in a car most people can reasonably afford at some point.

Sorry, new here, just trying to get this to work.

Getting back to the thread... Bolt on's are just that, bolt on's. Want to go fast and enjoy it? Build the engine yourself. Stuff some 11.5:1CR pistons in it, lightened up the rotating assy, build a custom short stack intake. (like downdraft webers, only Fuel Injected.) Port and polish the heads, put on a good exhaust system, ignition, flywheel, etc. Have fun doing it. Then beat the hell out of the turbo'd CRX down the street and smile like crazy doing it! Don't know how to build your own engine? Get some books, best investment ever! I'm an ASE, Subaru, VW certified tech. I love building engines. It's the next best thing to racing and great sex! <choose your own order on those two :) > Can you build a daily driver 2.5 with 300HP? Yes. Can you daily drive a 500HP 2.0 turbo? Yes. How happy you are driving it depends on how well you tune it! If you spend all morning to work and all afternoon from work from 5k-6kRPM in your car, build it for top end HP. If you're like the rest of us, build it for some torque in the midrange to upper range. The first one to build a screamin' 3.0 H6 wins a lolipop. Hey, I'm bluecollared and broke too. You can build a monste 3.0? Buy your own damn trophy, I'm out enjoying my car.

bump

Originally posted by N/A
So back to my comment about raising the compression from its 10 to 1 up to as much as 12 to 1. Has anybody tried it yet? It might not give the big hp gains but I'd imagine it would help out to give the car even more of the low end torque that makes the EJ25 so fun.

Here is a list of mods that I am doing now and in the future to my 98 2.5 RS.
-11:1 Forged JE pistons, wrist pins, rings
-port/polished heads
-valve springs with titanium retainers
-Cobb Spicy Cams
-polished/overbored throttle bodies (yes, that's plural)
-custom made intake manifold (doing it myself so it might not work)
-at first I am going to run it with the stock intake manifold and 1 throttle body. Then when I get some money I am going to do 2 throttle bodies and if that works, i might try 4
*note* I am doing all of the mods except for the dual throttle bodies at first.
-Stand alone ECU (Motec, Tec-II, Haltech, something?) I don't know if I am going to need it at first. I hope not!
-Fidanza Flywheel
-Vitek 4 Puck Carbon Clutch
-STI engine, tranny and pitch mounts
-some kind of air intake
-higher flow fuel pump and bigger injectors (if/when needed)
-I am going to be balancing and lightening the crank & shot peening the rods.
I am doing all of this work (machining, assembly, fabrication) myself, so this is goign to take a few months because I still have to work, take classes and try to make enough money to pay off my thousands of dollars in debt.
If you guys have any suggestions, let me know.

With all the other stuff you are very definitely going to want a TEC-III or equivalent fully tunable system to take advantage of all the flow. The stock unit will either severely underutilize the VE of your motor or simply fail to work at all. Plus, you can build near 100% reliability in any motor with good tuning. You'll find plenty of help around here when you get deeper into this project, a ot of us would love to see what that motor would be like.

is the fidanza flywheel the aluminum one? I have heard a lot of sketchy history of this flywheel. Your best bet is a lightened ONE Piece (not two or three like the aluminum flywheels) chromoly flywheel. they are stronger and more reliable.

Originally posted by ImprezaRSX
is the fidanza flywheel the aluminum one? I have heard a lot of sketchy history of this flywheel. Your best bet is a lightened ONE Piece (not two or three like the aluminum flywheels) chromoly flywheel. they are stronger and more reliable.

"Lightened" is a misnomer. A true 'lightened' flywheel is an evil piece of junk, where somebody takes a stock flywheel (usually one that already trashed) and shaves it down and drills the snot out of it to make it lighter. But a good one piece flywheel should be ok if you aren't abusing it. Chromoly is definitely best though.

What ECU do I need to run everything and how much am I going to have to spend. Like I said, I am not doing the independent throttle bodies right now. That will probably be a summer project. I might not even be able to afford the cams yet. Can someone please help me??? BAN SUVS, you seem to know quite a bit about this, please help. I am so used to old hotrods that have no computers or fuel injection. This is new territory to me. I understand that this ECU is going to cost me, but I don't want to spend $3000 on it! What about the TEC-II, why won't that work? I thought that was a stand alone ECU also? How about the Link? I was also looking at Haltech and Motec. Which one is going to do what I need for the best price, and whom do I buy it from to get the best price?

Nathan

You're going to have to shop around. Prices fluctuate alot. Generally, you can get a base standalone for around 1500. when you start adding features is where the money is. For example, a TEC III with a Suby Harness and necessary hardware is about 2250. That's a really good system, but a lot of work.

Originally posted by ImprezaRSX
is the fidanza flywheel the aluminum one? I have heard a lot of sketchy history of this flywheel. Your best bet is a lightened ONE Piece (not two or three like the aluminum flywheels) chromoly flywheel. they are stronger and more reliable.
I have a Fidanza aluminum flywheel on my Legacy, and I also have one on my Mustang. In both cases the quality appeared to be very high. Thus far (20,000mi, 7 track days, numerous auto-x events, and 2 trips to the drag strip) the Legacy flywheel has been problem free.

I've heard nothing but good things about them - what have you heard?

Pat Olsen
'97 Legacy 2.5GT sedan

I heard the ring gear and friction surface seperate from the flywheel.

That's just something you don't even have to risk with a one piece.

I decided the very first real mod (K&N doesn't really count) is going to be a set of Borlas. Since dRu888 apparently already sold his, I'm looking for a vendor. Is there anybody beating Gruppe S's price?

I think we have strayed a little from the topic of this thread.

IF, IF, IF.... If I put dual SB350 one for each rear tire with pulling cams that redline at 3K and then just directly linked them to the axle with nothing but a clutch I could go 400mph and do the 1/4 in 10 with the tires spinning the whole way. But am I no.

What the guy probably wants to hear is:

$1K in parts will get you to the 190Bhp range
$2K in parts will get you to the 220Bhp range
$3K in parts will get you to the 245bhp range
add $1K in certified tuning to the above and you will get maybe 10 more hp and more drivablity.
$5K in parts will get you to the 275 range.

If you spend $100K you can trade you EJ25 for a custom long block that can be spun to 11K rpms and the fuel management to make 700+ hp.

If you can do the work yourself, you will save money.

Bottom line is that you will not make power without fuel and air getting in the motor. Then you have to have the correct mixture to get the power. Spend you money on a Fuel Management system of your choice and your will get power. Everything else after that is to allow more air to go in through the motor.

Tim (aka Captian Obvious) :D

(Sorry, just reread this and I got a headache trying to get through it. I did some grammer corrections so not to look like a complete idiot.)

Originally posted by tim smith
What the guy probably wants to hear is:

$1K in parts will get you to the 190Bhp range
$2K in parts will get you to the 220Bhp range
$3K in parts will get you to the 245bhp range
add $1K in sertified tuning to the above and you will get maybe 10 more hp and mroe drivablity.
$5K in parts will get you to the 275 range
Tim,

I hope the above numbers were just provided as an example of what you think the guy wanted to hear, and were not provided as fact. If there are provided as fact, then I hope you were talking about turbo kits or NOS.

There's not a snowball's chance in hell that $2000 worth of parts is going to get a N/A 2.5L up to 220hp. Based on personal, dyno-proven experience, $4000+ worth of parts will get you in the 205-210hp range. It will take lots and lots more money to get a N/A 2.5L up to WRX levels, let alone STi levels (275hp).

Pat Olsen
'97 Legacy 2.5GT sedan

Originally posted by Patrick Olsen
Tim,

I hope the above numbers were just provided as an example of what you think the guy wanted to hear, and were not provided as fact. If there are provided as fact, then I hope you were talking about turbo kits or NOS.

There's not a snowball's chance in hell that $2000 worth of parts is going to get a N/A 2.5L up to 220hp. Based on personal, dyno-proven experience, $4000+ worth of parts will get you in the 205-210hp range. It will take lots and lots more money to get a N/A 2.5L up to WRX levels, let alone STi levels (275hp).

Pat Olsen
'97 Legacy 2.5GT sedan

You're probably right Pat. I expect about 195-200 hp with cams, headers, and exhaust, plus intake. And that's plenty, considering that nothing in the class of the RS is going to make more than that without going to FI as well. I'll be happy with it, and that will let me save long enough for a 6mt and turbo kit. :D

The power lies in headwork with properly matched camshafts. But you also have to take into consederation a good flowing induction as well as extraction system to match the flow of the heads. I'd put half of my total engine budget towards the heads, n/a or not.

The key here is getting a properly matched set up.

-scu.

No they were various parts to get it to those power levels. Includings cams, SAFS, etc. No NOS. I don't believe in it. And they were not vendor quotes just educated guesses. I could easily get those power numbers with the above money. But I do my own work. Sorry to mislead on that point. If you do some looking you can do anything with almost any reasonable amount of money. With a couple of sponcers you could get the above work done for free (plus the time you invest). All you have to do is tell a company that you will drive your car around with thier logo on it if they provide X amount of money and the Logo will grow with the amount of sponcered money. But that is really beyond the scope if this thread. Sorry again to mislead, but they are examples of what I could do with that money. Edit: And the power measurements were at the crank.

Tim (Have a good weekend everyone because I will!)

Added like 2,000 members since this was responded to, anybody else want to chime in? :D

I dont know Pat, I seen a Dyno chart for someones RS that only had a catback, pulleys, and intake ( I think, it was minimal compared to the work that you done) and they dynoed 3HP lower than you did. Maybe the SOHC engine responds a little differently to mods. I figure that once I buy a SAFC, Cat, and Cams at income tax time, I should be over 200 HP with the following mods.

Ganz with K&N
Borla->TWE Cat->Stromung Catback
N1 Style Pulleys
Cobb Cams
PROECM Chip
APEXI SAFC

After this, I'll probably just do little mods like Boring the TB and such until I get my down payment for my house taken care of.

Now serving #101...bump

Hello everyone (DCoty especially). I have a new plan of attack on the intake manifold. My professor looked at the stock one and he decided that he wants to design one out of sheet metal, but we'll have to wait a month or two until i get the heads flowed, ported and the engine back in the car to test it once it's done. He knows his stuff inside and out and has tons of experience with all types of racing and engines. I can't wait until this car is done. I have decided to take out a personal loan to get everything at once; engine, suspension, braking, ecu, etc. This car is going to be mean when it's done. I'm shooting for the highest hp naturally aspirated without doing bottom half work. When I build that 12:1 block, that will make it the end all monster N/A beast! Muwhahahahah(insane laughter).........

Nathan

P.S. Dan, how's the car. I called LaChute about valve springs and Ben hasn't gotten back to me. I have been calling almost every day, but it seems that he is always in a meeting or out with a customer. Drop me a PM or post on here. Lata.

Did any of you guys subscribed to this thread see the dyno chart for i-Speed's RS with the Ludespeed kit? 245 hp/285 ft.lbs. at the wheels, with no other mods! That's Double the horsepower, with a near-flat curve for $4300 plus some tuning, maybe $400 or so. No chance at doing that N/A for that money.