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Old 07-31-2001, 03:16 PM   #1
RaceCarRiot
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Member#: 6542
Join Date: May 2001
Chapter/Region: South East
Vehicle:
1997 Ver IV
silver

Default project: 93-97 impreza intake.

i REFUSE to put anything that says weaponR on it under my hood.

i REFUSE to put some cobbled together/hacked up airbox DIY intake under my hood.

so i'm setting out on my quest to build a REAL 93-97 intake. anyone who wants to contribute any info is welcome.

since the weaponR (makers of fine stickers and license plate frames) and JC sports intakes (bleh) are the closest things we have to intakes tailored to our cars, let me start by asking the owners of either:

what are their weaknesses? any design flaws? could they be used as a starting point for something that actually WORKS?

over and out for now.

adam.

(edit: apparently, i can't spell when i'm at work.)
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Old 07-31-2001, 03:24 PM   #2
MPREZYA
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I would try and make one that comes with a plenum that is similar to most of the stock ones but is larger since minus the plenum of most stock intake systems you lose some low end torque. Make sure it uses 3" piping and includes a heat shield and catch can. Course it would probably cost @100-150 to make and sell at close to $250-300 but then most people wouldn't pay for a $300 intake unless it's CARB approved for us Californians.
Good luck and hope it helps.
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Old 07-31-2001, 03:34 PM   #3
ins8ibl
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How about a smooth tube, that is connected from the throttle body to the MAF, that is connected to a nice cone filter that fits inside a modified stock airbox. That way you would get some sound, cold air, and no vibrating the MAF to death.
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Old 07-31-2001, 08:32 PM   #4
rx
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I'd start off by doing tests on the original intake to actually find out how bad it is first. You can do this with a manometer. There is nothing really wrong with your intake if the reading is less than 5 inches.

If there are any major (proven) restrictions there, you'll see where they are and how they can be improved.

Building something from scratch with no background info like this is like running in the dark. I would suggest against remanufacturing your own plenum chamber as the chances are you, a welder and say $100 worth of stainless steel are not going to match Subaru's multi million dollar development efforts. There is a reason why all EJ20, 22, and 25 Imprezas and Libertys run basically the same system.

I can say the same for all the J-pipes - I agree, I don't think they perform as they should, and I dare say they are just a copy of a lot of Honda designs and don't have enough development behind them. A difference of + or - 10 inches in the length of an inlet pipe can mean 10 hp throughout the rev range. I doubt the manufacturers of the j-pipes dynoed different lengths and diameters. It's a black art and it costs them too much.... just as long as it's nice and shiny then they'll buy them... and in my opinion looks are not what a performance intake is about. Not bagging anyone in particular, but I've tried j-pipes and I've reverted (happily) to a stock setup, and now to my own 'ganz style' CAI with a WRX cold air rubber tube running to the front brake duct.

When you use your own tubing with this intake, I would suggest trying a number of different diameters - 2.5, 2.75 and 3.0 inches.

I would use the manometer to test for restriction, and then use the smallest diameter tube that causes no restriction. You'll get better torque with this method as the velocity of the intake air will be faster, than (for arguments sake) a 4" pipe. I personally think 3" is too big. The throttle body itself is only 2.75" and the inlet to the standard plenum is 2.5". The rest of the diameter is just unused and slows down velocity. This is one of the reasons why the standard intake feels so smooth, linear and torquey.

This weekend I'll actually be testing for positive pressure in the brake duct area with a U-tube manometer. Recently I read an aerodynamic article on an MY99 WRX and it showed there is a lot of positive pressure around the bottom of the headlight and around that brake duct. I will be conducting tests to work out how many inches of water (positive pressure) it creates at various speeds. I will also check and see if an STi style fog lamp cover will smooth out the flow in that area and create more pressure.

Anyway, that's my rant - hope it inspires some thought. Keep the suggestions coming...
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Old 08-01-2001, 08:44 AM   #5
RaceCarRiot
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silver

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rx--good points all around. i definitely can't test different lengths of tubing, as my "R&D" budget for this whole project won't go over $350-400.

also, i just did a general web search on "impreza intakes" and found a few interesting bits, namely some intakes that aren't available in this country because let's face it...no one's paid much attention to subaru in the US until the WRX was released.

this may or may not be a solution...you're in sydney, right? have you seen anything over there that might be an option for older impreza owners on this side of the pond?

i saw somekind of GC8 intake made by apex that looked like it would work pretty well, but the page was all in japanese...
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Old 08-01-2001, 06:58 PM   #6
subystyle
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2000 Impreza 2.5RS
Sedona Red Pearl

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We are hard at work building an ntake that will work with the early generation cars that have MAF's. We should have something definite in the next couple of weeks. The prototype that we have been testing on a 00' 2.5RS has showed considerable gains in Horsepower AND Torque. Contact me with any questions.
Gary Williams
Compass Motorsports
"Pointing You in the Direction of Performance"
503-816-8136
503-366-0874 (fax)
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Old 08-01-2001, 07:55 PM   #7
rx
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We want to see photos and dyno sheets Gary.
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Old 08-01-2001, 08:05 PM   #8
rx
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racecar riot - there's basically only two types of intake you can buy for an NA impreza over here... we were shadowed from the very beginning as the WRX has been here the whole time.

You can buy a Unifilter pod that goes straight onto the throttle body. If you like, you can see what they look like at www.uniflow.com.au

A popular Sydney based Impreza workshop (figure it out, I don't like to incriminate workshops) also sold a JC sports / Rallispec type J-pipe with a Unifilter pod on the end.

Both types eliminate the factory plenum box and seem to go OK when you first get them... but it's that wild sound that is deceiving. In the long run, I much prefer the plenum box.

Your gripes with the Weapon R intake will re-occur if you make your own j-pipe setup. They're all fairly similar in design, just that the weapon R is a bit shorter. It's not worth taking this approach, although it's safe to say a longer j-pipe would offer more torque and power through the rev range.

The thing I like about the stock plenum box is it's punchy at low revs. If you're a traffic light racer, what do you want... a car that bogs and stalls and then has heaps of power at 3500 - 4000rpm. You end up with a car that isn't enjoyable anymore (at least that's what I found). The stock plenum box makes it go, whatever rev range you're in, whenever you want... punchy. Much more streetable, finito.

I look forward to seeing Compass Motorsport's solution.
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Old 08-01-2001, 08:06 PM   #9
subystyle
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Sedona Red Pearl

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Here is the dyno run on my 00' 2.5RS with the prototype in question. The peak numbers were 185.4HP and 196.3ft/lbs.
Pictures should be ready around the end of the week or early next week. That is approximately when the first production box will be done.
Gary Williams
Compass Motorsports
503-816-8136
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Old 08-01-2001, 09:09 PM   #10
Inferno
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Forest Green Impreza L

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I have the Weapon-R Dragon Intake in my car and it hasn't given me any problems yet.It really is working wonders for my car but that is only my opinion.
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