·$3 Catch can
·BOV dump tube

Page Updated:
Nov. 17, 2001


© 2001
Tom Gilmore

Best viewed at 1024x768

(The usual disclaimer applies to this installation: you proceed at your own risk and I am not responsible for any damage that may or may not occur as a result of following these instructions, ok?)
Cut the BOV dump tube (2G DSM)

Remove this blockage in your intake and make some cool sounds with your BOV!

Click HERE for a printer friendly version

Free mod - why do it?  

The BOV dump tube mod is one of the easiest mods you can do, and it's also free! It will free up a restriction in your intake that Mitsubishi engineers purposely installed to reduce the noise that a turbo car makes. Strange to think but most people would probably freak if they heard the car sucking & hissing after every gear shift. So this tube which routes excess air from the BOV (blow off valve) back into the intake dumps it far away from the filter and reduces the noise. It also happens to get in the way of the air rushing towards your turbo, theoretically reducing your power. This is no good! So read along and see how to free up the air and add some cool sounds to your turbocharged car while you're at it!

Tools required  

This is a very simple mod, but you need a few things to do it right. This includes:
* A few screwdrivers (duh)
* A hand saw or hacksaw
* JB Weld
* A piece of PVC tube (optional - see below)

The 'how to' steps  

1. Remove the air filter

For this install, I'm going to assume you have replaced the stock air box with a high-flow filter like the K&N FIPK. (If you still have the airbox it's easy to remove - check the links below for a page on how to do that part first.)

a] Loosen the clamp holding the Mass Airflow Sensor (MAS) to the rubber intake hose.
b] Remove the bracket holding the air filter in place (if needed).
c] Unplug the MAS - carefully press the clip in and pull it out.
d] Take the filter & MAS right out and set them aside for now.
e] Unscrew the clamps on both ends of the hose that comes out of the BOV.
f] Unscrew the T-clamp that holds the turbo intake hose to turbo itself.
g] You can also move the coolant overflow bottle to help make room. Just lift it up and it will slide out of its mounting bracket.

2. Remove the turbo intake hose

Ok now you should see something like the picture to the right. That long hose that extends way down into the turbo intake hose is the infamous BOV dumptube. This is what you will be removing soon. Notice how there was oil on mine. This is from the valve cover breather hose. To fix this problem, read my $3 catch can page !

a] Remove the three hoses attached to the turbo intake hose (see picture). Just pull gently on the end and they will slide off. I suggest you label these with a piece of tape so you know which one goes where when you put them back on later !!
b] Slide the bottom end of the intake hose off the turbo housing.
c] Take the turbo intake hose right out and set it aside.
d] GENTLY stuff a clean rag or some paper towels into the turbo housing so you don't get any crap in there while you're busy working on the rest of this mod.
3. Loosen the tube

a] Remove the curved hose with the two clamps on it from the turbo intake hose. Now you can see the top of the dump tube.
b] Use a flathead screwdriver and break off the grey glue stuff all around the edge of the dump tube.
c] Insert the screwdriver between the dump tube and the side of the rubber intake hose to gently pry it apart. Don't remove it yet.
4. Cut the tube or replace it ??

Now you have two choices. You can either:
1) Hack the dump tube [SEE Step 5A]
2) Replace it with some PVC tubing [SEE Step 5B].

The choice is up to you, and either is fine. If you decide to cut the stock tube it's not reversible but are you ever going to undo this mod anyways? Probably not. If you go the PVC route, you can keep the tube and return the car to stock someday if you need to.
Personally I just cut the thing up.
5A. Cut the damn tube !

a] From step 3c, the dump tube should now be loose and ready to pull out. BEFORE you do, make a mark on the side of the dump tube about 1" from where it enters the rubber intake hose. This is roughly where you are going to cut it.
b] OK, now you can pull the dump tube out. Hey what do you know, it's actually made of plastic! Take some time to clean off as much of the old grey glue around the tube as you can.
c] Put it in a vice to hold it still and using your saw, cut that puppy along the line you marked. In my case, this cut the tube about in half. It should be at a slight angle too (see the picture). If the cut is rough, smooth the edges out with a file. You can now throw the bottom half away! Go to Step 6.

TIP - Now is a good time to clean that oil out of your rubber intake hose before you put the dump tube back in.
5B. Save the tube - use PVC !

a] From step 3c, now pull the dump tube out and put it away.
b] Go to a hardware store and pickup a piece of PVC tubing, with these dimensions:
* Length - 3 to 4" long (cut to suit your purpose)
* Inside diameter - 1"
* Outside diameter - 1-1/4"
This chunk of PVC will now act as your 'dump tube'. Follow on to Step 6 for the rest of the instructions.

NOTE: The bottom half (accordian-like part) of the rubber intake hose in the picture to the right was cut off so a section of hard pipe could be used instead. That's not part of this install and you don't need to do that or worry about it.

(BIG thanks to Todd Hynes for the photo!)
6. Put the tube back in

a] Mix up some JB Weld and smear it on the side of the dump tube. If you kept the stock tube, just smear it back where the old grey glue was. On the PVC tube, just smear some around the top of the tube, and leave about 1/2" clear at the end of the tube that will be sticking out.
b] Insert the dump tube back into the rubber intake hose. Push it in slowly and wipe any excess JB Weld off.
c] LET IT DRY ! JB Weld requires an hour (or more) to set properly. If you use JB Quick, I think it only needs about 10 minutes to set. To be safe I let it sit overnight but if you're in a hurry give it an hour at least.
d] Relax - you're almost done!
Try to twist the dump tube inside the rubber intake hose - it shouldn't move if it's dry.
7. Reinstall the intake and go for a cruise !

a] Take that rag or paper towel you put into the turbo inlet OUT !
b] Put the intake hose back in the engine bay, and reattach it to the turbo inlet first with the T-clamp.
c] Take the curved hose that goes from the BOV to the dump tube and reattach the two clamps on each end loosely.
d] Hookup the 3 hoses that you removed from the turbo intake hose in Step 2 (you DID label them right ??).
e] Reattach the BOV hose to the BOV outlet.
f] Reinstall your air filter (or airbox) and MAS.
g] Reattach the turbo intake hose to the MAS and plug the MAS back in.
h] Tighten ALL your clamps back down firmly.

DOUBLE CHECK ALL your hoses and clamps to make sure you didn't miss one BEFORE you go for a test drive!!

All done!  
Congrats - you're finished! After you've double-checked all your clamps and hoses take the car out for a spin! You should notice that the BOV is much louder when you shift. If the car stumbles, you probably forgot to hook a hose up properly. Enjoy the new sounds and tiny increase in power.

* Jeff Mitchell - for the basic install procedure.
* Todd Hynes - for the PVC option and many tips!

Some additional reading on this subject is available here:

Click HERE for a printer friendly version