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Old 07-29-2000, 04:07 PM   #1
BrianX
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Member#: 1923
Join Date: Jul 2000
Location: Lincoln University, PA, USA
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2000 2.5RS
BRP

Question MY00 Mods = ??? HP? Where to go from here?

I have a MY00 with the following engine/exhaust mods:

Stromug Single Tip Exhaust
Stromug Midpipe
K&N Drop-In AF
UR Underdrive Pully

According to Cobb Tuning, this is good for a 10% power increase. (181.5 HP?) Does anyone have any dyno numbers to back this up? Or another opinion? Seems like 16.5 HP jump is a bit... Optimistic. (Unless the stock Subaru setup is that restrictive...)

The next question is... Where do I go from here? No one seems to know exactly how to hook up the Super AFC, so I've got a bad feeling about that... Borla Headers? The turbo prices are really steep, and I drive 80 miles a day round trip, so comprimising reliability/drivability isn't an option... And I don't want to lose my precious low end torque...

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Old 07-29-2000, 08:22 PM   #2
Memnoch
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You wouldnt lose your low end with a turbo. YOu'd just have your car running like it always does until the turbo starts doing its thing

I think you'd have to go with the S-AFC, or if you care about handling (you should) you could get a sway bar, like the whiteline. It's adjustable and from what I hear its very nice. That'll be my next mod right now. And maybe the Stromung midpipe. I'm not sure how the car will change with the midpipe if anything at all..
 
Old 07-29-2000, 08:28 PM   #3
Imprezer
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Have a Nice Day?

Why would you be comprimising reliability/drivability with a turbo? I mean if some local muffler shop will put one kit for you then yeah, you are in trouble. But if you get a good turbo kit and good engine management you will not be compromisng anything.
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Old 07-29-2000, 09:01 PM   #4
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Yeah Imprezer posts like yours is what we all need, reassuring of the turbo way
That's the path I'm gonna take after xmas comes, hopefully
 
Old 07-29-2000, 09:48 PM   #5
MattJP
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What is good engine management??
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Old 07-30-2000, 05:16 PM   #6
Reciprocity
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Question

Hey BrianX, what springs did you use for those STi struts??

D. Neil ".5" Crawford
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Old 07-30-2000, 05:24 PM   #7
brandon
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Origionally posted by Memnoch
"You wouldnt lose your low end with a turbo. YOu'd just have your car running like it always does until the turbo starts doing its thing"

No offence to anyone, but I cannot understand why there are still people who believe the above. Of course you loose low end with a turbo installed. Until the turbo spools up, it is just a really big exhaust restriction. It is true that limited amounts of exhaust restriction may improve torque in some motors (hence the playing about with variable exhausts in the eighties), but we are not talking about a small restriction here. This is not a debateable point.

As far as reliability goes, I've never heard of anyone with an aftermarket turbo or supercharger kit not having to fiddle with it. I don't think BrianX was trying to infer that the turbo will break, just that when you drive 80 miles a day the last thing you want to do is start playing with things when you get home.

Brian, I think it's time for you to think about suspension brakes etc. It seems you've done what you can reasonably do to the motor without spending lots more money and time. You'll get more bang for the buck (performance wise) out of tires, brakes etc. from now on... unless you do decide to take the leap to forced induction -which is never a bad thing, just time consuming and expensive-. If you do decide to go forced induction at some point, and are the type of person who wants lots of low end torque, go for the supercharger instead.

[This message has been edited by brandon (edited July 30, 2000).
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Old 07-30-2000, 05:34 PM   #8
shiv
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Brandon-- I think you're overstating the effects a turbo has on low end torque. If one were to stick a backpressure gauge in the header, he would probably find no measure backpressure at idle, cruise or any low load situation. Generally, it's only under boost that backpressure will rise. Holding all things equal, you would be hard pressed to find any difference in low end torque between an NA car and one that has a turbo.

Shiv
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Old 07-30-2000, 10:07 PM   #9
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Old 07-31-2000, 12:50 AM   #10
BrianX
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Turbo is a warrenty problem though... I want anything I do to be easily un-doable should I have a warrenty issue.

SuperAFC and headers seems to be the only thing left... (Or the Cobb Pigyback job...)

Suspension is another thing, I've got that taken care of...

Cusco 21mm Rear Bar.
Sti V5 Inverted Struts.
Custom Primitive Racing Front Tower Brace.

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Old 07-31-2000, 02:45 AM   #11
brandon
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shiv, I definately respect your opinion but on this one I have to disagree. There is always a power loss in a turbocharged engine before boost arrives. As very quick and dirty proof, look at JC Sport's dyno chart (the first one I could find, I don't have a lot of time for writing). In thier chart it looks like boost comes on around 2600-2700 RPM and there is lots of extra power above that point. But below spool up there is an obvious power loss. This is very typical of every dyno chart I've ever seen comparing a Turbo to it's non turbo counterpart. Don't get me wrong, I'm a big fan of turbos and even did my thesis on a modified type. When I have the time and money my car WILL get forced induction because I see it as the most intellegent way to get real power.

There is more at work in the exhaust than just backpressure (although I think that is the major source of power loss - but I could be wrong), there is also the scavaging factor which is heavily dependent on "header" length and diameter. Throwing a turbo in the stream does not help things out from a design basis. Of course the size of the turbo and its particular characteristics (mass, moment of inertia, frictional losses, turbine blade design, etc.) will have a dramatic effect on when spool up occurs, but below that point...always a power loss. That loss may only be a few hp, but when you've only got 50 or so available (at low RPMs) 5 or 10 hp can seem like a lot. Especially when stuck in traffic or pulling a trailer.
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Old 07-31-2000, 03:34 AM   #12
brandon
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1964 Lotus Elan

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shiv, I was thinking some more about your statement about the backpressure guage and have come to the conclusion that there would HAVE to be a pressure difference across the turbine. Otherwise it would not work. The turbine in a turbocharger requires 3 things to operate (well...it only requires two but 3 are much better); a pressure difference, flow, and a temperature difference. There are two ways to create the flow, the first being backpressure (the pressure difference, othersise known as "head" when working with fluids - you can insert your own joke there) and the other being expansion of the hot gas out the tail pipe. It is no secret that the turbine in a gasoline engine requires both the heat AND the pressure difference to operate efficiently, although what percentage each contributes I have never found any literature on. However, if you look at a diesel engine you will quickly realize that in it's case pressure plays a much larger role. The results of which are a significantly faster spool up time even though diesels run much cooler than spark ignition engines.
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Old 07-31-2000, 06:07 AM   #13
BrianX
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BRP

Post

That's what I get for typing too many things while the Wife is nagging me...

Low End Torque Loss Question: Do the Borla Headers reduce the low end torque?

Turbo/Supercharger comment: I work like 50 hours a week, and I'm currently on call every other week. I drive between 1.5 and 2 hours a day. It's not currently feasable to tweak a system every night when I get home. With the MY00, everything I read says MAP can't handle above 1 bar of boost, so a {Super|Turbo}charger and all the baggage that goes with it isn't for me. I've even debated having RalliSpec install and tune the system, but...

The SuperAFC doesn't give me the warm fuzzies on the MY00 yet... The debate on the narrowband O2 sensor before the cats, etc... It almost seems mandatory, since with the intake and exhaust mods, I am getting a bit of subtile backfire on shifts...

Suspension is a comparatively easy game, I understand it and what I want for the most part, and it's just stuff (parts, etc) specific to the scoober that I'm still learning.

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Old 07-31-2000, 07:55 AM   #14
brandon
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I don't know much about the Borla Headers in particular, but properly designed headers should not reduce the low end...as long as the tubes aren't huge. As far as the MAP question goes for the 2000, you're right in that it doesn't seem to have maps for anything above atmosphereic. However, if you were to go with shiv's TEC setup, it replaces the origional MAP so boost would no longer be a problem. You seem to have everything well in hand so have fun. I just wish I had the money/time to do these things myself. Spring maybe.
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Old 07-31-2000, 11:03 AM   #15
GT2RS
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Question

Brandon,
Can you explain forced induction a little bit more please! Right now i have very similar mods and curiosities that BrianX have. Thanks!
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Old 07-31-2000, 04:35 PM   #16
brandon
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GT2RS, that would make a very long post. I did one about a year ago for the message board for the Toronto 2.5RS Club. If you go there it MAY be in the archives. I say that because the site has been through a few revisions and it may have been lost. I'll see what I can dig up though. I wish I could say I've got time to write something else up right now, but it would be impossible. However, the first book I ever read on the subject is fabulous and very inexpensive. If you watch the site I'll post the name and author of the book. It's only $20 but it will give you the best introduction to forced induction you'll find anywhere. And really, the best way to make choices for your car is to keep yourself informed. There's a lot of mis-information around about turbos/superchargers which makes it difficult to make an informed decision. For all you know, nothing I posted above might be true (it is though).
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