Here are the step by step instructions... - Saab NG900 & OG9-3 Bulletin Board -
The banner above is an advertisment - if it asks you to download software, please ignore.
Site News - 2/5 T-Shirts All Sent Out! Last Call! | 1/6 Saab Owners' Convention 2023

[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Performance | Detail | Clubs & SOC | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Service/Mechs | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

NG900 & OG93 Bulletin Board
1994-2002 [Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main NG900 & OG93 Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Here are the step by step instructions...
Like This Post:
Posted by REM in Seattle [Email] (#4) [Profile/Gallery] (more from REM in Seattle) on Tue, 9 Nov 2004 20:34:35 Share Post by Email
In Reply to: Air filter box intake mod, Gary Cims, Tue, 9 Nov 2004 18:37:34
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

These instructions work great for the 1994-1998 NG900 and the 1999 9-3. I have personally done this modification on MY1995, MY1998, and MY1999 vehicles.

REM in Seattle
2005 Saab 9-3 Aero Convertible; 5-speed; 500 miles
1998 Saab 900SET; 5-door; Automatic; 73,000 miles

By Rob Mustard (aka REM in Seattle)
Search word: rem_mod
Last updated – March 10, 2003

Enlarging the factory New Generation (NG) 900 Turbo airbox inlet tube is easy and allows for far more air to enter the airbox. First off, the factory NG900 Turbo airbox has a 2” (51 mm) inlet tube that goes from behind the front right headlight/bumper to the airbox. There is a 2 1/2” (64 mm) outlet from the airbox to the turbocharger inlet. Therefore, the 2” inlet tube is the first restriction to more airflow.

Note that there is an opening in the front of the Saab NG900 from just above the right front fog light, thru the sheet metal, to the airbox inlet tube. This should allow ample fresh cold air for the airbox intake. The front lip of the airbox intake tube can actually be seen by using a flashlight and looking up into the opening above the right fog light. If the vehicle is moving at all, the air will increase in pressure in front of the fog light, just like it does in front of the radiator, bumper, etc. This high-pressure air will move through the opening in the bumper above the fog light, through the large opening in the sheet metal to the airbox intake tube.

In my case I replaced the factory 2” intake tube with a 3” intake tube for more airflow. The area of the 2” diameter inlet tube is approx. 3 sq. inches (20 sq. cm), while the area of the 3” diameter inlet tube area is approx. 7 sq. inches (46 sq. cm) or more than double the area of the factory inlet tube. Add a high performance panel air filter (like the K&N #33-2663, Amsoil #TS88, or ITG #WB-364 air filters) in the airbox to eliminate even more intake flow restriction.

The front of the factory airbox is approximately 3.25” across. The PVC pipe I chose is labeled 3” PVC Drain and Sewer and has a 3.25” outside diameter with a .080” wall thickness. Thin walled PVC electrical conduit would probably also be suitable. The standard Schedule 40, and DWV (Drain/Waste/Vent), 3” PVC pipes have a .210” thick wall and are 3.5” diameter, and so will be too wide to fit the front of the factory airbox. Thin wall 3” PVC Drain and Sewer pipe, or thin walled PVC electrical conduit pipe, should be available at most home improvement or plumbing supply stores.

I chose PVC because it is easy to cut, easy to shape with a heat gun, and is widely available. The use of PVC tubing in this application should not pose any hazard as the airbox inlet tube is far enough away from the engine heat to make melting or softening a non-issue, and if the PVC should break or shatter due to an impact, the engine air filter will keep any PVC fragments from entering the engine intake. I later wrapped my PVC intake with a fiberglass ‘pipe repair kit’ for more strength and impact resistance. Wrapping the PVC pipe with a high temperature duct tape is another option. Aluminum tubing (like irrigation pipe), Fiberglass tubing, or Polypropylene (like a leaf blower tube), would also be good choices for the intake tubing. For the best results a smooth internal wall and a flared opening (bell mouth or trumpet shape) at the front of the inlet tube are needed. These will help minimize losses in the intake flow.

1) Start by removing the grill, right front headlight assembly, and right turn signal assembly.

2) Pay special attention to how the current inlet tube sits in relation to the bumper and headlight assembly. You will want your new 3” inlet tube to sit in nearly the same location.

3) Remove the factory airbox from the engine compartment.

4) Measure the length of the factory inlet tube from the front of the airbox to the end of the tube (mine was approx. 10 inches).

5) Cut a piece of 3” PVC tube 1 to 1 ½ inches longer than the measurement for the current inlet tube. The new 3” inlet tube will extend from the airbox the same distance as the old inlet tube. The remaining 1 to 1 1/2 inches will protrude inside the airbox. Preferably the 3” PVC pipe you have chosen has a bell mouth (trumpet shape) on one end to accept the next length of PVC pipe. This bell mouth works very well as the inlet tube air in take end near the front bumper. Alternately, a bell mouth can be formed on the end of the tube by using a heat gun or hair dryer to soften the PVC tube, and a funnel or similar tool to form the softened PVC tube. The bell mouth acts to reduce airflow losses in the inlet tube.

6) Using the 3” inlet tube as a pattern, mark a 3” circle on the airbox over the current inlet tube opening. Be sure that the new opening will be below the lowest point of the air filter element.

7) Cut the opening for new 3” inlet tube. I used a small jigsaw, a utility knife, and a course file, to cut and shape my new opening.

8) Fit the 3” inlet tube to the airbox and check the airbox and inlet tube assembly for correct fit in the vehicle. Reinstall the headlight assembly to be sure there is enough clearance. Trim the airbox inlet tube opening, the inlet tube, and the ribs in the airbox as needed to get the proper fit.

9) At this point I stopped to paint the PVC tube black. This is for cosmetic reasons only, to blend in with the rest of the airbox and tubing. Use lacquer thinner to clean the 3” inlet tube prior to painting. Alternately, the PVC pipe can be wrapped with a high temperature duct tape (like the aluminum duct tape) or fiberglass cloth. This will also help contain the PVC pipe in the event of a fracture.

10) Clean the airbox where the tube will mount with lacquer thinner. Tack the 3” inlet tube to the airbox in a couple places using hot melt glue. The hot melt glue is just to temporarily hold the new inlet tube during the clearance check. Check again to be sure that the inlet tube will clear the headlight assembly. Then completely seal the inlet tube to the airbox both inside and out using Black RTV Adhesive/Sealant. Be sure to keep the water weep hole in the bottom of the airbox clear.

11) Reinstall the airbox, headlight assembly, turn signal assembly, and grill.

Obviously, this is just one step in improving the airflow to the NG900 Turbo. A high performance panel air filter (like the K&N #33-2663, Amsoil #TS88, or ITG #WB-364 air filters) and a low restriction exhaust (like the Saab Sport exhaust) are additional steps that should be taken. Dean has also suggested that the plastic ‘silencer’ in the turbo intercooler inlet tube be removed, and that the abrupt edges in the throttle body transition housing (where the turbo intercooler outlet connects) in front of the throttle body be smoothed.

posted by 24.16.197...

_______________________________________ REM in Seattle Current: 2013 Volvo XC60 R-Design, Rebel Blue, 3.0L 6-cyl turbo, Automatic 2005 Saab 9-3 Aero Convertible, Steel Gray metallic, 2.0L 4-cyl turbo, 5-speed Former: 1998 Saab 900SET 5-door, Silver, 2.0L 4-cyl turbo, Automatic 1991 Alfa Romeo Spider convertible, Alfa Red, 2.0L 4-cyl, 5-speed 1984 Saab 900T 3-door, Red, 2.0L 4-cyl turbo, 5-speed

Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.


Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img][endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img][endimg] (or use the Optional Image Link field below).

Optional Link: (e.g.
Link Title: (Optional)
Optional Photo/Image Link: (e.g.
Photo/Image to Upload: (Please be patient while file uploads)
Swedish Dynamics
Jak Stoll Performance
Button Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2022 - The Saab Network -
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | on Facebook | on Twitter | Shop Amazon via TSN | Site Donations]

Random Member Gallery Photos (Click Image)

This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. has been a moderated forum since 1988. For usage guidelines, see the Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - | Run Club Menlo Park | ScreenBot

Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!