Welcome to the North American Subaru Impreza Owners Club Thursday August 21, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Normally Aspirated Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 05-03-2001, 04:29 PM   #1
Mako
Scooby Newbie
 
Member#: 5770
Join Date: Apr 2001
Location: Los Angeles, CA
Vehicle:
2000 Legacy Outback
Green with Stromung & CAI

Post Do It Yourself CAI

I've experimented with two self-fabricated cold-air intakes. The first uses a 2" PVC plumbing connector connected to the airbox tube via the flexible coupling that is a part of the stock setup on my MY2000 N/A 2.5L. The fit is perfect. From there I have a piece of black PVS 2" piping going to the hole in the fender. This setup pulls quite well throughout the powerband. Total cost $4.87.

The second option has a 3" to 2" connector attached to the flexible coupling mentioned above. A length of 3" PVS pipe goes to the hole in the fender where another 3" to 2" fits into the hole--the 3" pipe is too big. This actually seems to pull LESS well. Do you think it is because even thought the bigger pipe is 3", it is drawing air from a 2" diameter hole? Or am I imagining things?

I know these aren't as cool looking compared to Ganzflow and JC aluminum intakes, but it saves my $$$ for other mods, like rear 18mm sway bar.

Which setup do you think should perform better?
* Registered users of the site do not see these ads.
Mako is offline   Reply With Quote
Old 05-03-2001, 07:45 PM   #2
inpreza kid
Scooby Specialist
 
Member#: 3334
Join Date: Dec 2000
Location: Calgary, Alberta, Canada
Post

i'm not too sure but the 3" tubing should be able to pull a bit better. i think larry has the results on his website that compares his ganzflow 2" to the 3".
inpreza kid is offline   Reply With Quote
Old 05-03-2001, 08:23 PM   #3
IowaRS
Scooby Newbie
 
Member#: 5385
Join Date: Apr 2001
Location: Rapid City, SD
Vehicle:
2012 WRX Base
Ice Silver

Post

For a given engine rpm there is pretty much a fixed amount of mass flow rate of air.
mass flow = density of air x velocity x cross sectional area

The important parts of this equation for intakes is the cross sectional area and velocity.
If the mass flow and density are constant a larger area has to yield lower velocity.
A smaller area yields higher velocity.
Generally to acheive higher power more velocity is desired as it will tend to "pack" more air/fuel mixture into the cylinder. The more you can get in there the bigger the boom, the more power per boom!

Now there are of course limits to this because of fluid dynamics (in this case the fluid is air.

Extremely high velocities in small tubes can result in "choked" flow, which is basically restricted flow.

Haven't gone through the numbers to figure out which intake should theoretically be better because there are so many variables in engine performance.

The only way to REALLY tell which is better is with a dyno or a GTech.

BTW, what is Larry's website?
Here's mine: http://home.att.net/~tkjacobs/imprezapage.htm


[This message has been edited by IowaRS (edited May 03, 2001).]
IowaRS is offline   Reply With Quote
Old 05-03-2001, 10:26 PM   #4
Jessie James
Scooby Specialist
 
Member#: 2072
Join Date: Aug 2000
Chapter/Region: MAIC
Location: Out of my mind
Post

Heh! I just got done doing a home-made CAI myself! I took pics, which I *might* get developed sometime this year (because I lag) and it works pretty well.

Like I have any clue!

Okay, at least it SOUNDS cool!
Jessie James is offline   Reply With Quote
Old 05-04-2001, 07:12 AM   #5
HondaH8er
Scooby Specialist
 
Member#: 3097
Join Date: Nov 2000
Chapter/Region: NWIC
Location: www.rs25.com Beaverton, OR
Vehicle:
2013 Ford Focus ST
Performance Blue

Thumbs up

Larry's web site: www.imprezars.com
His current intake is a 3" tube, the previous one (which I have) is 2.5". I hear there isn't really a difference in power increase, since the opening on the stock airbox is only 2.5" where the intake connects. I think Larry said the main reason for the size change was because his first supplier stopped suppling, and he found a source for bigger, better finished pipe elsewhere. Either way, it's a great intake!

Myles

Edit: Nice website, Jacob! One thing I've heard, though, is that PVC pipe, when heated, gives of chlorine gas, and since that pipe is under the hood, it probably will get heated, and I don't think you want chlorine gas getting in the combustion chamber. I might be remembering this wrong, though...anyone else know for sure?

[This message has been edited by HondaH8er (edited May 04, 2001).]
HondaH8er is offline   Reply With Quote
Old 05-04-2001, 09:08 AM   #6
IowaRS
Scooby Newbie
 
Member#: 5385
Join Date: Apr 2001
Location: Rapid City, SD
Vehicle:
2012 WRX Base
Ice Silver

Post

After some quick research, you are right PVC will outgas for quite some time and it actually recommended against in vacuum systems. Which is really what an intake ends up being anyway.

Probably should take it off for risk of engine or sensor damage.

Thanks
IowaRS is offline   Reply With Quote
Old 05-04-2001, 09:20 AM   #7
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Post

Get an exhaust U-bend (mandrel bent, prefabbed piece) from Summit or Jeggs or something like that. I got a 15"-6" J-bend, cut where appropriate, and presto-chango, instant CAI (with the appropriate rubber connectors). $30, all up.

<IMG SRC="http://www.jetlink.net/~okayfine/DIYintake.jpg" border=0>
Julian is offline   Reply With Quote
Old 05-04-2001, 09:36 AM   #8
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Post

Hey that looks like a pretty decent piece of work there... would you mind posting all the pieces you had to get and where you got them from? (esp. rubber bits sizes)

[This message has been edited by BadDog (edited May 04, 2001).]
BadDog is offline   Reply With Quote
Old 05-04-2001, 01:14 PM   #9
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Talking

I think Summit or Jeg's has stainless steel pre-bent piping... maybe I'll try some of that.
Yep- www.jegs.com Hooker stainless mandrel j-bends for $20.99
part # 289-42426
OD: 2''
Radius: 3''
Leg A: 6''
Leg B: 15''



[This message has been edited by BadDog (edited May 04, 2001).]
BadDog is offline   Reply With Quote
Old 05-04-2001, 02:51 PM   #10
Frey Bone
Scooby Newbie
 
Member#: 6252
Join Date: May 2001
Chapter/Region: NWIC
Location: Bend, Oregon USA
Vehicle:
2000 GC8 w/STI
Blue

Post

Wonderfull, but what about those of us with a 98' I'd love to go to the auto store and get a K&N drop in (is ther a better one?) and then to Home De-Pot to get the pipes and reducers.....BUT what do I do with the MAS sensor, will it matter if I move it?
Frey Bone is offline   Reply With Quote
Old 05-04-2001, 04:06 PM   #11
Mako
Scooby Newbie
 
Member#: 5770
Join Date: Apr 2001
Location: Los Angeles, CA
Vehicle:
2000 Legacy Outback
Green with Stromung & CAI

Post

Julian--GREAT looking CAI! So it goes 2" to 2" connector at the airbox, to the steel piping, to the 3" to 2"?? Is that it? Also, is that a rubber boot wrapped around the piping at the fender, if so , where did you get it? I can't quite tell from the pic what you have going into the fender. Finally, is 15" of piping enough to reach from the bend to the fender. Thanks in advance!

Mako
Mako is offline   Reply With Quote
Old 05-04-2001, 04:55 PM   #12
Peaty
Techno Sapien
Moderator
 
Member#: 449
Join Date: Oct 1999
Chapter/Region: MWSOC
Location: Lawrence, KS
Vehicle:
2010 Legacy 3.6R Lim
Azurite Blue Pearl

Arrow

For the 99 I made my own. I kept the second airbox and secured the MAF nice and tight. So far over 20K and no problems:
http://www.azscooby.com/mods/AZScoob...stomintake.php

Peaty
Peaty is offline   Reply With Quote
Old 05-04-2001, 07:02 PM   #13
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Post

Mako,

The rubber boot around the pipe as it enters the fender is the 3" to 2" coupler. Both the rubber bits are home-improvement-store items. $5 out the door. The 15" length of the J-bend I bought is what is showing in the pic, it is uncut except for the angle.

Julian
Julian is offline   Reply With Quote
Old 05-05-2001, 12:54 AM   #14
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Post

Actually, it's much the same as Larry's setup, just a mild steel pipe versus Al. One pipe (aforementioned), one 2 to 3 inch plumbing coupler, one 2 to 2 coupler (they're actually nearer to 2-1/2"). Both couplers were found at Home Depot. Not much to it, but you have to have a way to cut the pipe (bandsaw is better than a hacksaw) and you gotta paint it inside and out to prevent rust (I plan on wrapping it in exhaust header stuff when I find some).
Julian is offline   Reply With Quote
Old 05-05-2001, 11:53 AM   #15
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Question

So, you cut the pipe right about
here || ?
\/
=====
// \\
// \\
|| ||
|| ||
||
||
||
||
||

And then rotate the short end 180 degrees, used rubber & clamping to seal that cut, and rubber fittings on either end to seal to airbox & fender?

[This message has been edited by BadDog (edited May 05, 2001).]
BadDog is offline   Reply With Quote
Old 05-06-2001, 12:04 AM   #16
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Post

OK, so i see ascii art doesn't work too well here ;-)
BadDog is offline   Reply With Quote
Old 05-06-2001, 02:07 AM   #17
HondaH8er
Scooby Specialist
 
Member#: 3097
Join Date: Nov 2000
Chapter/Region: NWIC
Location: www.rs25.com Beaverton, OR
Vehicle:
2013 Ford Focus ST
Performance Blue

Lightbulb

If ya'll want to see what BadDog was trying to draw, click the word "edit" at the bottom of that post, and you can see what he drew.
HondaH8er is offline   Reply With Quote
Old 05-06-2001, 10:35 AM   #18
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Post

Well I looked at www.jegs.com to order a mild steel pipe to practice on, and a stainless pipe for the final piece so I can give this a shot. But when I look at the specs, it'll say 2-1/2" OD (outer diameter, I assume) and * 4-1/4" radius * ... are they talking about the radius of the bend? I guess I'll order 2-1/2", since that's how big the opening on the filter box is anyway... then I gotta figure out where and at what angle to cut
Anyway, I'll probably screw it up and end up ordering one of Larry's anyway, LOL!

[This message has been edited by BadDog (edited May 06, 2001).]
BadDog is offline   Reply With Quote
Old 05-07-2001, 09:31 AM   #19
dirk.gecko
Scooby Newbie
 
Member#: 3141
Join Date: Dec 2000
Chapter/Region: MWSOC
Location: De Pere, WI
Vehicle:
2007 Scion tC
Blue or something

Post

Julian:

How much flexibility does that setup allow? Like when you punch the gas and the engine torques a bit on its mounts...does it allow for that?
dirk.gecko is offline   Reply With Quote
Old 05-07-2001, 09:37 AM   #20
tonytiger
Scooby Newbie
 
Member#: 3844
Join Date: Jan 2001
Location: Helsinki, Finland
Vehicle:
1993 Legacy 1.8
White

Talking

One day I removed all the intake system before the airfilter. I noticed that the car rised car much more smoothly and fastly. My car's intake system is more simply than in rs, but should have the same affect with rs's too. Posted one day a topic concerning the power increase on the basis of cold air. It shouldn't make much difference, since the air goes relatively fast in the pipe. --> air doesn't have much time to warm up... Well benefit = benefit. In turbo motors cooling the air is more important since the air warms when going through the turbine. I think the engine breaths more freely with CAIs and therefor it can increase top speed significantly. The last sentence is just a thought... Fuid dymanics are complicated. But mainly can be stated that blocks in the pipe (including curves and suchs) creates turbuline and reduces the Mass Air Flow. In the system of a motor when the sucking "power" depends on the underpressure the calculations gets even more complicated. Although the exact calculations can't be stated, above mentioned principles can be used...
tonytiger is offline   Reply With Quote
Old 05-07-2001, 11:20 AM   #21
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Post

I've not had the pipe move appreciably during revving while parked in my driveway. There is an additional length of the pipe stuck in the fender/coupler. I've had no problems, and I jump on it all the time. Just make sure the connections at the airbox are tight...that's all I'd be worried about.

As for what angle to cut it at...you can try to measure the angle. I don't remember what angle I used offhand, but thought I got it from one of Larry's posts about his intake (as I got all my ideas about this from his intake)
Julian is offline   Reply With Quote
Old 05-07-2001, 11:26 AM   #22
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Cool

Julian,
Did you use *only* the longer part of the J-bend and discard the short end? I made a flat cardboard model to figure out how to cut my stainless pipe when it arrives, and while doing so I noticed that I could probably use the stock 90 degree plastic curve that came out of the airbox, thus discarding the short end of the J. Up until that point, I was trying to imagine what cuts at what angles I'd have to make in order to use the whole pipe, and how you got it to form a tight seal with the airbox. I'm no engineer, so it started to make my brain hurt until I made a cardboard model I could experiment with, LOL.

I ordered a 2-1/2" pipe, so I guess I'll just need a 2-to-3 inch coupler for the fender, and a 2-1/2" -to- 2/12" for the conneciton to the plastic pipe from the airbox.

I decided to use stainless steel so I wouldn't have to paint it (I'm not very good at that!) inside and out. I checked out the prices of exhaust header wrapping and all the stuff you need to do it... it looks like it would double or triple the cost of the setup!

Now I've just gotta wait and try it out for myself, and maybe find out how to polish that stainless steel... :-)
BadDog is offline   Reply With Quote
Old 05-07-2001, 01:58 PM   #23
BHONE78
Scooby Newbie
 
Member#: 6397
Join Date: May 2001
Location: Ft Worth TX
Vehicle:
2001 R.S.
BLUE

Post

www.cobbtuning.com look at this cold air intake
BHONE78 is offline   Reply With Quote
Old 05-09-2001, 12:51 AM   #24
Julian
Scooby Specialist
 
Member#: 1182
Join Date: Mar 2000
Location: Ventura, CA
Vehicle:
MY00 RS
BRP

Post

BadDog,

Yes, I only used the longer length of tubing after cutting. I believe the angle was somewhere around 60degrees (or 120degrees, depending on where you're measuring from). It should be easy to figure out. Straight cut as well, nothing fancy.

The Cobb intake is a nice piece...however this is about 1/10th the cost.

Stainless is a good way to go. Wish I'd thought of that!
Julian is offline   Reply With Quote
Old 05-09-2001, 02:15 PM   #25
BadDog
Scooby Newbie
 
Member#: 3725
Join Date: Jan 2001
Location: Oswego, NY
Vehicle:
2013 Impreza/73 240Z
Pearl White

Post

Julian,
Thanks for the info. But you can still go stainless... it'll only cost you another $24 and some hacksaw time
The largest diameter stainless Hooker bend is 2.5", AFAIK
I've gotta find out what it'll take to polish it, though....
BadDog is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Do any of you know of a Do it Yourself Carwash jayscoobiedoo Mid Atlantic Impreza Club -- MAIC 5 11-16-2005 05:55 PM
Do it yourself or leave it to the pro? JOHN16V Interior & Exterior Modification 5 03-03-2003 04:41 PM
When you want it done right, do it yourself. Pics inside... ChosenWon Interior & Exterior Modification 20 10-29-2001 01:15 PM
Do It Yourself CAI SubieKidTK Legacy Forum 6 07-18-2001 05:05 PM
Looking for info on do-it-yourself 2.5L exhaust dvancleve South West Impreza Club Forum -- SWIC 7 04-03-2001 05:30 PM


All times are GMT -4. The time now is 02:09 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.