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Old 05-26-2003, 09:00 PM   #26
BAN SUVS
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Quote:
Originally posted by joefocker20
I wouldn't give that engine a second look.. This winter, I'm going to try saving enough to buy a USDM STI block and Ludespeed Stage III turbo kit..
Joe, are you one of the lucky 6 in Evergreen?
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Old 05-26-2003, 11:46 PM   #27
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No, but I have a feeling that these will be extremely easy to come by. I was actually thinking that getting a JDM front clip might be cheaper than a built engine w/ a USDM block and turbo kit, plus you get a sturdy tranny also..
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Old 05-27-2003, 01:23 AM   #28
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Originally posted by HndaTch627
actually it wouldn't do anything except make the car run cleaner, they aren't making more power with the AVCS system, they are stretching fuel economy and getting the car in under the emissions laws.

jeremy
Yeah, I know the purpose of it. Is the Subaru AVCS just timing, or does it change lift/duration like VTEC? My thoughts were if it had separate lobes like Honda, to add a manual controller (VTEC Controller?) instead of leaving it computer controlled. Then you have some cams ground with one set of regular stockish lobes and some really aggressive race lobes. For daily driving you leave it on the stock lobes, retaining driveability and mileage, then at the track, a simple flip of a switch puts you on the "big cam". Pull into the staging lanes, car sounding all smooth and stock, reach up and punch a button on the dash and suddenly start lobing like crazy. Follow it up with a nice nitrous purge. And that would be "sweet"
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Old 05-27-2003, 01:39 AM   #29
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Originally posted by jasona


Yeah, I know the purpose of it. Is the Subaru AVCS just timing, or does it change lift/duration like VTEC? My thoughts were if it had separate lobes like Honda, to add a manual controller (VTEC Controller?) instead of leaving it computer controlled. Then you have some cams ground with one set of regular stockish lobes and some really aggressive race lobes. For daily driving you leave it on the stock lobes, retaining driveability and mileage, then at the track, a simple flip of a switch puts you on the "big cam". Pull into the staging lanes, car sounding all smooth and stock, reach up and punch a button on the dash and suddenly start lobing like crazy. Follow it up with a nice nitrous purge. And that would be "sweet"
I'd hit it.
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Old 05-27-2003, 01:50 AM   #30
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Originally posted by BAN SUVS


Yeah... when Honda guys try to throw their power 'boost' from VTEC in your face... just point out the fact that Honda is actually taking AWAY power before the switch, rather than adding any.
hrrmm I thought that it had different cams to make the engine more efficient.

A smaller cam with less left and such for low rpm use,

then a bigger, high breathing Cam for high end use.

Or are you saying that honda cannot make a cam correctly?

I think their idea is great.

I also like ( I think it is Mercedes) Infinatly adjustable valve control system. They do not even need a throttle body anymore, because the can adjust the lift and timing as needed. It is like a dynamic version of Vtech.

Also companies are starting to use varible length intake runners to make an engine more efficient.

I am not defending Honda, but I think equipment that is designed to adapt to rpm is genious!

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Old 05-27-2003, 02:14 AM   #31
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Originally posted by RawCode
hrrmm I thought that it had different cams to make the engine more efficient.

A smaller cam with less left and such for low rpm use,

then a bigger, high breathing Cam for high end use.

Or are you saying that honda cannot make a cam correctly?

I think their idea is great.

I also like ( I think it is Mercedes) Infinatly adjustable valve control system. They do not even need a throttle body anymore, because the can adjust the lift and timing as needed. It is like a dynamic version of Vtech.

Also companies are starting to use varible length intake runners to make an engine more efficient.

I am not defending Honda, but I think equipment that is designed to adapt to rpm is genious!

RawCode
It's not a bad idea at all. It's the reason 180hp Civics can get 40 mpg. But the idea that you are gaining power from the VTEC isn't true... if you had the VTEC lobes on the only cam in there, it would stil be that strong, but it would suck gas (and make no power) down low. VTEC just trades torque for fuel mileage.

BMW makes the valve system you are talking about, it's called Valvetronic (catchy, eh?). Once they master that and gasoline direct injection gets more refined... the sky's the limit. You'll see 50 mpg V8's and 300hp, streetable 1.8l turbos.
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Old 05-27-2003, 02:26 AM   #32
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jasona- Subaru's system just adjusts cam position therefore changing valve overlap and intake valve timing continously. It is not designed like VTEC where it has 2 seperate cam lobes which are acutated by oil pressure controlled by a spool valve/solenoid.

Ban Suvs-your comment about honda losing power before it switches to the high lift cam was rather uneducated. Show me a camshaft that has a stable idle, runs super clean and doesn't loose power @ 7200 RPM the RS cams run out of breath at 5600 RPM and have a horrid idle to put that into perspective. It may sound like i am being malcious but just trying to show you from a different perspective.

Have Fun guys.

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Old 05-27-2003, 03:50 AM   #33
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Quote:
Originally posted by BAN SUVS


It's not a bad idea at all. It's the reason 180hp Civics can get 40 mpg. But the idea that you are gaining power from the VTEC isn't true... if you had the VTEC lobes on the only cam in there, it would stil be that strong, but it would suck gas (and make no power) down low. VTEC just trades torque for fuel mileage.

BMW makes the valve system you are talking about, it's called Valvetronic (catchy, eh?). Once they master that and gasoline direct injection gets more refined... the sky's the limit. You'll see 50 mpg V8's and 300hp, streetable 1.8l turbos.
If they used the same big cam on the low end, idle would suck and people would complain that Honda Engines seem rough on low rpms.

There is many reasons to use two different cams, I don't think they do it for milage though, a small cam just makes more power on low rpm. I think with a bigger cam, they would actually make less torque and HP on the low end.

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Old 05-27-2003, 08:10 AM   #34
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Ferrari's system (whatever it's called ) instead of 2 different cam lobes, has one long slanted lobe to give a smooth progressive changeover. That's pretty cool...

don't know what my point it, but I'm bored and can't sleep
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Old 05-27-2003, 01:25 PM   #35
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Originally posted by BAN SUVS
It's not a bad idea at all.
I just don't think it's as wonderful as the Honda crowd likes to tell everyone it is. It's an advance, and it's clever engineering, but it's no different than a lot of neat little things people have thought of to improve the ICE. As far as being forced to deal with a lumpy idle or no high end power, I disagree. There are scores of cars now with 250+ horsepower, one cam profile, and very smooth, clean-burning engines.
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Old 05-27-2003, 04:43 PM   #36
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Originally posted by BAN SUVS


I just don't think it's as wonderful as the Honda crowd likes to tell everyone it is. It's an advance, and it's clever engineering, but it's no different than a lot of neat little things people have thought of to improve the ICE. As far as being forced to deal with a lumpy idle or no high end power, I disagree. There are scores of cars now with 250+ horsepower, one cam profile, and very smooth, clean-burning engines.
So by having one cam, wouldn't they have had to make a compromise in some fashion? Less power on high end to make a stable idle and clean burn? An OEM manufacturer surely wouldn't use any overlap on its cams would they? I don't think it would pass emissions. (IIRC)

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Old 05-27-2003, 05:36 PM   #37
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hrm, I'd say put the valve train on the 2.5 block, then get some lighter pistons, and forged rods, and spin the 2.5 up to 71. That would be impressive, but I doubt the 2.0 heads flow enough to have that make sence. Though, there is one way to find out.
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Old 05-27-2003, 06:21 PM   #38
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You could use the twin turbo 2.0 heads, as they are rumored to be the highest flowing units of all.

I like the Ferrari's system idea, must be really expensive to produce.
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Old 05-27-2003, 09:15 PM   #39
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well... my rational was that the valve train was designed for 7000k rpm's which would make them pretty durable...
but if you took the internals from them, and put them on 22's or 25s you'd prolly get similar results...
makes me wish I had skills in the engine building department, a garage, and lots o' cash
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Old 05-28-2003, 12:29 AM   #40
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Quote:
Originally posted by m750
hrm, I'd say put the valve train on the 2.5 block, then get some lighter pistons, and forged rods, and spin the 2.5 up to 71. That would be impressive, but I doubt the 2.0 heads flow enough to have that make sence. Though, there is one way to find out.
http://forums.nasioc.com/forums/show...hreadid=304758
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Old 05-28-2003, 09:18 PM   #41
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jasona
The converse of what you said is that a 2.5L will spool a turbo faster, thus not needing the extra RPM.

Kostamojen
Quote:
Thats 186hp WITHOUT tuning! Just think about tossing on a full exhaust and your normal other bolts ons like a Cobb intake, pullies, etc... Then tune the variable-valve system via ECU for even more hp... Mmm.
True, you do get 31 extra h.p., but you have to factor in the cost of getting the motor, ECU, etc. I bet it is not good bang for the buck, especially with the reduction in torque. EJ25s can make 230 h.p. through the stock intake manifold, I suspect that the EJ20 engine being discussed would suffer the same fate.

HndaTch627
Quote:
not to sound like an ass, but thinking that you can spin an EJ25 reliably NEARLY as fast as an EJ20 is just maddness. the 2.5 ROd if just TOOO long, it's built for low end torque nothing more. You all bring up the torque issue. Torque is eliminated with a properly geared trans(which the RS very much does NOT have). well anyhow i'm not gonna sit here and paper race. but look at the foot per minute od speed of a EJ20 @ 8k rpm and look at the FPM rod speed of an EJ25 @ 8k RPM
The EJ25 rod is only just over 1mm longer than the 2.0L. That is approximately 0.9% longer. You are not talking big numbers here. In fact….if you put a longer rod in an EJ20 you get a better rod ratio. Rod ratio is something that all the Honda guys are obsessed with. The king of Honda REV-ing, the F20C (S2000 motor), has a 5mm larger bore and runs a rod ratio of 1.82. It runs a rod that is over 21mm longer than the 2.5L rod. Obviously the long rod on the F20C is not hindering its ability to make top end power.

The externals are responsible for the power drop off, not the rod length. The cams and the intake manifold on the EJ25 are poor for high RPM power. True a STOCK 2.5L might not do high RPM very well, but build it for high RPM with the right lightweight internals, appropriate flowing intake and exhaust set-up, and cam profiles that are suited to high RPM use, the story changes. But that is the type of stuff that the high REV-ing Honda motors do from the factory.

A lot of the ideas that people have about the 2.5L not making power at high RPMs should be put to rest when I finish my motor.

EJ25 with a slight overbore
Light rods
Light pistons
Light wrist pins
Custom cams
Custom header
Individual throttle bodies
Oil system modifications
Upgraded valve springs
Titanium retainers
Timing belt system modifications
Modified water pump
Lightened crank (maybe)
9,000-10,000 RPM

We will see if we can reprogram the factory ECU to work with the set-up. I do not yet know if it can sample data fast enough to deal with those kind of RPMs…….but we will see. There will also be a lot of fun with trying to get a factory idle air control system to work. I am shooting for over 320 h.p. on a car that is daily driven. Being that it is my only car. I don’t pretend that it will be easy to drive, but I am hard headed and I want to prove a point. Built properly a 2.5L can REV with the best of them.

Last edited by scoobiejosh; 05-29-2003 at 06:50 PM.
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Old 05-30-2003, 08:20 PM   #42
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Well..............looks like I shut this one down.
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Old 05-31-2003, 02:53 AM   #43
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Originally posted by scoobiejosh
Well..............looks like I shut this one down.
actually for what you said you made sense except you forgot somethings, the S2k breaks the laws of engine building by leaps and bounds, something subaru has never done. and FWIW if you want to waste all that money and make 250HP it's fine by me but you ahve to remember trying to rev a boxer is like trying to rev a V, the harder you push th quicker they break. look at how many people have spun rod bearings already. are you ready to waste 7k on mods that will not even make 300 hp?? i am sure a lot of people here aren't. in any case good luck.

and it's not rod ratio i am referring to, it's rod speed, FPM traveled by the rod itself.

Good luck.

jeremy
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Old 05-31-2003, 02:53 PM   #44
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actually for what you said you made sense except you forgot somethings, the S2k breaks the laws of engine building by leaps and bounds, something subaru has never done.
Honda’s best work is in the flow of the intake system and being able to have an aggressive cam while still passing emissions. Their heads flow awesome and they can do better resonance tuning with the intake manifold because of the layout. VTEC is a very clever emissions tool. You have the little cam to pass emissions, and the big cam to make top end power. It was brilliant in the late 80’s when it was released, and it still works very well now, especially with addition of the variable cam timing on VTECi equipped Hondas. The stock S2000 head outflows ported B-series heads (which in turn flow better than some ported heads). A Subaru cannot have one plenum for all four runners and have a runner length that is short enough for high RPM power like an inline four. Also, the runners of the manifold on the Subaru hit the ports of the head at an angle which is very poor for high flow. Honda shortblocks are frankly not the best, and that is what this conversation is primarily about. Their castings are not special (they are low pressure sand cast), they break cylinder walls easily, and their stock rod bolts are weak. Also, the only support that the Honda main bearings have come from a bolted-on main bearing placed at the bottom of the block. In fact Subaru is ahead of them on the bottom end. They have much better castings (high pressure die cast) and the rods are beefier. The main bearings are supported by a whole half of a block, which is much more rigid that a bolted on main bearing.

Quote:
and FWIW if you want to waste all that money and make 250HP it's fine by me but you ahve to remember trying to rev a boxer is like trying to rev a V, the harder you push th quicker they break.
That is true with any motor, inline, V, horizontally opposed, or rotary. That makes sense. ITR motors usually have to be rebuilt every 50,000 miles for the sole reason they are being pushed so hard.

Also, you are wrong about not making 300 h.p. It has already been done on a N/A Subaru in a SYMS car. It was and EJ20, but the extra displacement will only help.

Quote:
look at how many people have spun rod bearings already. are you ready to waste 7k on mods that will not even make 300 hp?? i am sure a lot of people here aren't. in any case good luck.
I get to see and help with Subaru motors being built almost every day, so I get to study a lot of failures. Most high RPM failures are in the valvetrain and have nothing to do with the bottom end. Most of the time spun rod bearings on Subarus happen under high load, mid-RPM situations under boost, not because of an inherent design flaw of the motor.

Quote:
and it's not rod ratio i am referring to, it's rod speed, FPM traveled by the rod itself.
EJ25 Bore – 99.6mm
EJ25 Stroke – 79.0mm
FPM - 4130.08 @8,000RPM

F20C Bore – 87.0mm
F20C Stroke – 84.0cm
FPM - 4382.4 @8,000RPM

Rod speed is not what most people look at, but rather piston speed, because the speed of the rod itself has little bearing on things. As you can see with a basic piston FPM calculator that the F20C is running more piston FPM than the EJ25. A factor that not everyone may take into account is that longer rods (with the wrist pin in the proper location) side loads the piston a lot less than a short rod. That means less friction on the side skirts and rings with the cylinder walls and less stress on the rods themselves. Thus you have less chance for piston and ring failure as well as less friction to rob power.

Rod length, ratio, and FPM are just part of one big huge equation. You cannot say that a rod length or piston speed (only looking at the bore and RPM and ignoring other factors) is going to make or break a motor. When you look at all of the variables the EJ25 can be a great REVer and with the appropriate intake and exhaust flow, be great for top end power. I am not saying the Subaru motor is superior, but it has different strengths and weaknesses, and once you address the weaknesses you have a great motor on your hands.
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Old 05-31-2003, 03:06 PM   #45
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I forgot to mention that the Subaru EJ series (or boxer motors in general) are naturally amongst the most well balanced factory motors made. The balance of the motor has a big bearing on how they perform at every RPM, including high RPM. The better the balance the better chance you have of making power and getting a little more longevity while doing it.
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Old 06-03-2003, 03:58 AM   #46
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I just keep having this run through my head:

SOHC EJ25 + Full exhaust, Cobb Intake, lightweight pulleys, lightweigh flywheel + proecm/etc. chip = Less than 200hp

Granted, thats not alot of mods, but with the EJ20-R you only need 14 more hp to get to 200 and I think those mods will push it over that limit, especially if combined with ECU re-programing... Can we say possibly 220hp without even doing internal work/cams???
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Old 06-03-2003, 04:49 PM   #47
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I wouldn't mind having a high RPM, more HP/less torquey engine...actually I'd prefer that over an engine with a lot of low end torque.
What does a light FWD car need a lot of torque for anyway? I'm not towing anything and would just spin the tires with too much low end power.

I'm thinking an EJ25 probably isn't the best choice for an engine swap for me. A high spinning NA EJ20 would be pretty cool though - 200+ HP would be more than enough power.
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