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Old 06-21-2001, 02:37 PM   #1
MINDGAME
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2002 2.5 TS Wagon
No, it's not a WRX...

Default NA vs. Turbo

I really dig my new 2.5, but obviously want to make some adjustments. I got the 2.5 over the WRX because I really liked its low-end torque, and knew that putting a turbo on it at a later date was always an option. So my first inclination was to go turbo, as that offers the most potential for my car. But since this is a daily driver, and its not uncommon for me to drive 200, maybe even 500 miles in a week, I started to consider going all-motor. I saw the combined gains maxing out at an estimated 210hp (intake, full exhaust, cam, ecu). When I was looking at going deeper into the motor by replacing the pistons and doing headwork, a friend warned me that if I was going NA to improve reliability, then I was going in the wrong direction. He told me that internals like this need constant attention, and that such a car would be less reliable than a turbo.

I may take my car to the track once in awhile, but am more interested in driving through curved country roads at 100+. I'd like to see my car in the 230-250hp range, but want to go the route most reliable. Could somebody please give me some personal advice? Or show me some studies/articles to read? Thanks.

(I have also posted this message in the NA forum)
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Old 06-21-2001, 02:45 PM   #2
peepshow
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Default

Let me be the first to say, welcome and NEVER cross-post! The moderators don't like that. Anyway, I would not be concerned with reliability and going turbo. Lots of people have racked up lots of miles with turbo 2.5s. You run into trouble when you get boost greedy. If all you are looking for is 250 or so hp, you should be fine running a turbo kit at 5-6psi. At those boost levels I don't think that reliability will be an issue. Talk to Trey from www.cobbtuning.com or Ed and Pam at iSR(www.autocaresubaru.com). Good luck.
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Old 06-21-2001, 03:01 PM   #3
jmott
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who is your friend and why does he think he has a clue (he may or may not)

Theres three kinds of NA mods that can reduce reliability.

1. Increased compression (This is equivalent to adding boost actually, except the boost is always on)

2. Spinning to really high rpms.

3. Boring your motor out to increase displacement


If you can get the power you want from head/intake work, cams, and bolt ons. Do that, it will be something you can beat on all day without worry.

otherwise, it kinda depends.
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Old 06-21-2001, 03:02 PM   #4
omahasubaru
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Default Peaco

Look for Peaco. They sell built subaru N/A motors on exchange. I have one of their catalogs and they have some impressive numbers, I'm just looking to disect them a bit more.

They build EJ22's and EJ25's and "6cyl" So I don't know if it's the 2.7 (XT-6) or the 3.3 (SVX) motor.

They have some nice N/A motors probablly close to your hp wants. I'm curious as to how daily drivable friendly these are, but as everyone will say.. you can build a nice Turbo for less than you can create a N/A equivalent, but the power delivery would ROCK on the N/A.

227 hp N/A 2.5 -vs the new WRX.. I think we both know who would win that fight.

Jon
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Old 06-21-2001, 03:22 PM   #5
MY99 2.5GT
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Default

There are certain things you are going to have to replace with that kind of power increase whether its NA or Turbo. I will stay away from them because they show no advantage or disadvantage to NA over Turbo or the other way around.

I personally would go the turbo route. Firstly me personally, I would never do any turbo application without a TEC-II programable ECU. Many people will say this is overkill and to buy a less expensive motech or haltech or wolf, that these work with your stock sensors. Let me just tell you that your stock sensors were not built or meant for anything much more than a stock engine. The Tec comes with a new ignition system, 550 fuel injectors, a nice knock sensor, a high resolution crank trigger sensor, an onboard boost controller and a few other fun things that you can do all through a lap top.

I think it would be much easier on an engine to have a properly tuned turbo system with properly managed timing, ignition, and fuel/air mixture. I think you can even setup different profiles for your car. Such as a gas mileage profile for long trips. Or an Auto-X profile that could also differ from a track performance profile.

Sure a built up NA setup won't hurt your engine as much as a poorly tuned turbo setup will. But a properly tuned turbo setup will blow right past a built up NA setup and still have similar reliability.

Just remember going the cheap route is always more expensive in the end than buying qaulity products.

Thanks
Brad
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Old 06-21-2001, 03:32 PM   #6
Rich L
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go with the turbo and use the money you saved to buy suspension or body mods.
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Old 06-21-2001, 03:33 PM   #7
Jon Bogert
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Up to 230 HP (@5-6psi) a 2.5 turbo requires no aftermarket engine management whatsoever. The fueling can be handled by <$500 worth of hardware.

I don't believe anyone is making that kind of power NA without a higher redline and some sort of $900+ (unichip, etc) fuel and timing control. Correct me if I'm wrong.

Much more than 230 HP and you will need aftermarket electronic fuel and timing control whether you're turbo or NA.

No question that 230 HP seems to be a real sweet spot. More than that and you're adding and changing a whole lot of stuff.
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Old 06-21-2001, 04:06 PM   #8
mirror70
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xxxxx

Last edited by mirror70; 12-27-2007 at 12:06 AM.
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Old 06-21-2001, 04:47 PM   #9
Jon Bogert
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220-230 HP is the "conventional wisdom" flywheel output of a 5-6psi turbo RS. No-one, to my knowledge, has pulled their engine and set it up on a dyno, so flywheel numbers are guesstimated from those few AWD dyno charts that we have available. Since there are huge driveline losses, not to mention inefficient dyno losses, there's a huge fudge factor in any published numbers.

But in the end does it really matter if you're making an actual 220 or 230 flywheel HP? The performance speaks for itself, with 1/4 mile times in the high 13s reported by people with this setup.
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Old 06-21-2001, 04:55 PM   #10
boondoggle
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Default Re: NA vs. Turbo

Whatever you do, save some money for track time.
100+ on public roads is not such a good idea.

Quote:
Originally posted by MINDGAME
I may take my car to the track once in awhile, but am more interested in driving through curved country roads at 100+.
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Old 06-21-2001, 04:56 PM   #11
NickSTi
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umm riiiiiiight
Quote:
Many people will say this is overkill and to buy a less expensive motech or haltech or wolf, that these work with your stock sensors. Let me just tell you that your stock sensors were not built or meant for anything much more than a stock engine.
the motec is MUCH more expensive than the tec 2. I will flat out say the tec 2 is INFERIOR to the motec period. the haltech is debateable, but not the motec. just try to tune that thing where the car is mapped on a per cylinder basis. You need a motec tech guy to get u past first base. Also you do not need to use stock sensors with the motec or haltech; you can buy additional sensors. The motec goes for around $4200 btw.

Quote:
The Tec comes with a new ignition system, 550 fuel injectors, a nice knock sensor, a high resolution crank trigger sensor, an onboard boost controller and a few other fun things that you can do all through a lap top.
you mean the vishnu performance system does. that is something entirely different to what you are trying to say. bigger injectors and an on board boost controller are stuff that vps packages extra and have nothing to do with the behavioural differences between the *tec* systems.

Quote:
Just remember going the cheap route is always more expensive in the end than buying qaulity products.
and common sense really isnt that common. sometimes when people tell you something is absolutely necessary, and you hear it from enough people enough of the time you lose all common sense and start to post silly things

Maybe if I ever end up at the track with imprezident Nick we will see how inferior those *other* setups are
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Old 06-21-2001, 06:15 PM   #12
mirror70
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Default

xxxxx

Last edited by mirror70; 12-27-2007 at 12:05 AM.
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Old 06-21-2001, 08:29 PM   #13
Kevin Thomas
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Default Engine management

I've ran over 40K without any aftermarket ECU in my car (With turbo and Nitrous) and my car runs fine even still. I don't get it. It isn't necessary to run an aftermarket ECU but it will be helpful in tuning, no doubt!

This debate/argument is getting spicey. Carry on!

BTW: I'm all for the N/A 2.5RS. Not because of potential but just because it's different and you don't see a lot of powerful N/A 2.5RS's around. Andres Rodriguez in Texas has that 2.5RS I'd love to have. 14.484@94.49mph in the 1/4 mile can't be all that bad. I love it!
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Old 06-21-2001, 09:19 PM   #14
NickSTi
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Hear Hear kevin.
I think i said that in another post.
You do not have to have an expensive ecu kit

It seem no one recalls the time MattC, Joe Hogan, and Efoo I think it was dynod their cars and one was running piggyback electronics and got similar gains. I know the argument isnt gains but reliability. Kevin Thomas runs a stage I turbo and Nitrous with piggyback equipment. Adam bloom used piggy back electronics for a long time and even though his motor died in the end I bet the piggyback electronics werent the problem (he was using stock injectors and a stock fuel pump iirc)

Obviously you dont want a stock ecu controlling the spraying of injectors almost twice stock size, but there are some mods u can get away with using apexi and j&s stuff
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