DIY: Air box mod

[Justincredible]

Ok I did this a while back and thought I would post this up. I know there is the debate about the open element and the stock air box. From what I can see the open element doesn't seem to do much good (or at least that is the thought {I have never tested one my self} ). So with all the info showing that the open element is not going to be big on hp I thought I would look at the stock Air box and see where I could do better.

What I found is a Valve that is in the bottom of the air box. This valve is closed at any thing below 5k. After 5k the valve opens up and lets in the extra air the car needs. This valve is attached to a ram air snorkel that goes all the way down to the front bumper to allow in more air (ram air) Even with the Valve open all the way the unit was kinda bulky and IMHO restricting some air. So I removed it and WOW I could almost not feel any more power.

The results were as expected. To make sure I was not hurting the performance. I logged the MAF values I noticed a 20GPS increase across most of the band above 3400 to about 5100 where I only noticed about 5-8 GPS more.

Conclusion.
There was a rise in the GPS of the MAF. This tells me that on the same day with the same temps removing the Valve allowed the car to take in more air past the MAF. So the car was taking in more air. Worst case I am just allowing the car to get more air sooner. I would stack that up there with a K&N filter. Not going to change the car into a monster but it is going to help let some more air get into the motor But for free.

The work took all of 45 min from start to Finnish. The only real work was there is a vac line that runs the Valve. I traced the line back to the intake and capped it off.

I was going to post more pic's but I can't my Audizine folder won't let me put in any more

[jaybquick@JHM]

Good job. That is just like the OEM B5 RS4 inlet with that trap door. I yank them out on all the B5 RS4 air boxes we install and it does help. Nice to see some of this simple DYI stuff showing up in the B6/B7 S4 forum.

[poopypants]

Nice write-up. So since there is more air coming into the manifold, i take its cooler air from the lower ram air therefore slightly better performance? a fraction of less fuel consumption?

[Justincredible]

you know what. My dumb a@@ never thought to check and see the IAT. I would have to assume that they are the same if not cooler due to the fact that they are not going into the engine compartment the same way the main Air duct is. There is also one other Air duct that goes back and grabs cold air from the passenger side fender up by the door. There is a tube connected to the air box for that as well. Well it isn't directly connected but it goes into the back side of the air box. I completely removed that tube as well.

[Monchichi8]

Post more pics! I think I'll do this today! thanks.
P.S. If your outta room here on the Zine use photobucket, its free!

[whartung]

yeah i'd be curious to see more pictures. I can't quite get a grasp on what you did from the description alone.

[Justincredible]

Post more pics! I think I'll do this today! thanks.
P.S. If your outta room here on the Zine use photobucket, its free!

I have lots more pic's so I will go sign up for photobucket now and try to get more up later tonight. I would like to get more room for the Zine as it was so easy to put them up here

[mbgt72]

I read about this a while back and really wanted to do this but couldn't find much info or any dyi. Thanks for posting, and i can't wait for more pics and info.

[ieatfishburitos]

Don't you think just opening the valve and leaving the ram air setup would be a better option? My guess is that standing still in a garage it looks better without the ram air setup connected, but moving down the road where the actual ram air ducting is forcing air into the box would be the best situation?

[likewater]

Ok I went ahead and did this mod today. The job is simple especially if you've had the air box out before. I used to have the Strat Hyperflow and went back to the stock air box with a K&N. Car runs much better with the stock box. After removing the valve, what I got was a noticeable flat-spot in the acceleration when you mash on the gas. I had this same flat spot when I was using the Strat. Overall, I'm not too worried about it because the car seems to pull just as hard if not "just" a little bit harder. Although maybe it's my imagination because I also noticed that the nice sucking sound you get from an open air filter has now returned. Not as pronounced of course, but there is definitely a difference. So I'm still up in the air on this one but will drive with it for a little while to see.

In the end I don't really think this makes a bit of difference. The only "real" performance changer this car is going to see is the VF SC. God bless forced induction.

[Justincredible]

Don't you think just opening the valve and leaving the ram air setup would be a better option?

You just remove the Valve but in the second pic you see the part where the ram air hose goes to.

As I stated there is a GPS raise for this in the MAF reading. There is going to still be the flat spot up past 5k this is when the Valve would normally open so at that point you are just getting in a better amount of air but not too much more.

All I can say it that I proved it tonight at the 1/4 mile drag strip. I will post more info about this later. But I have to wait till the people I am working with on some of the performance parts for my car say I can talk about it

[momoney]

yeah i'd be curious to see more pictures. I can't quite get a grasp on what you did from the description alone.

Same here More pics please.

[Justincredible]

Ok I realized some of my pic's I guess that gives me more room for Zine storage.

So these pic's will help out but if not let me know I can get some more. I just thought this might be better then some of the pic's I have.

There are 3 spots for Air to get in the Box
1 from the front of the car threw the main air scoop (on the front of the car and then connects to the top of the air box.
2 on the Back side of the air box there is a adapter that dead ends at the front of the passenger door (this is labeled in green)
3 the flap controled by vacuum in the bottom of the Air box. (this is in red)


As you can see I have two colors.
Red. This is going around the flap in the bottom of your air box this is what you want to remove. There is a flap and if you look in the second pic. you will see I have removed the Valve from mine. If you remove your Air box you will see there is a Valve that's there. This valve is restrictive below 5k It is restrictive due to the fact that it is shut.

You want to remove this. To remove the valve you need to remove the air box. That is kinda straightforward im sure there are several wright ups on this but I can post how to do that if needed.
OK so you have your Air box removed. Take off the top and take out the Air filter. Throw away the pre filter if you still have it as this is just one more thing that can clog. After the removal of the filter you will expose the bottom of the air box and doing so you will see the Valve in the bottom of the box.

The goal is to remove the Valve and not damage the mouth to the Bumper ram air intake. Removing the Valve is easy. Take off the Vac line and cap it off with a screw in the line or with a proper vac tap. There is a lot of extra Vac line that you can trim back if you wish. The vac line runs from the Valve to the front of the intake manifold. So trim it back as far as you feel comfortable.

Now that the Vac line is dealt with lets remove the Valve. To do this Look at my sec pic here you see there are 2 ph screws on the side. These are holding the Valve and the mouth to the ram air connection together in the Air box. Remove these 2 screws. Don't loose them as you will need them. Now that the 2 screws are out the mouth and the valve can be removed. With the mouth and valve being one unit you will remove them and separate them. After you have the Valve separated reinstall the Mouth in the air box

Now you can either just reinstall all the parts or you can go to step 2 and remove the tube (circled in Green) from the inner fender wall. To do this remove the passenger side tire. Then remove the inner fender liner. There are like 15 torx screws for this (not sure the exact #) but they are all easy to get to. After you remove the inner fender liner. Pull out the tube and throw it at something because at this point you have 10,000 scratches on your hands. After that just button it all back up and you are good to go.

Disclaimer /////////////////////////////////////////////////////////////////////

I never said this is going to be the biggest Hp gain but for free it is definitely one of the best for the money. As I said the car will get more air from this I and a few other people have Verified this threw the MAF value increase.
For free there is no reason why not to do it.

Feel free to let me know if you have any other questions or if I didn't do a good enough job with the pic's and explanation

[poopypants]

i tried this mod a lil bit ago and there is no such opening. Mine is an 04 S4, so i would think this only applies to the 05's. The only intakes are the ram air from the front and the side fender. Oh well, at least i tried.

[Justincredible]

Poopy,

So you removed the air box completely and no hole on the bottom? HMMM well that kinda sucks. Did you get a pic of the air box? are you a manual car?

I would definitely like to find out why there is no additional air intake on your box

Sorry that is not cool at all

[99PanozAIV]

[QUOTE=Justincredible;3014409]


Great image. Where did you get that...service manual?

[Justincredible]

Great image. Where did you get that...service manual?

yes they are quite expensive but they do have lots of good info

[poopypants]

Poopy,

So you removed the air box completely and no hole on the bottom? HMMM well that kinda sucks. Did you get a pic of the air box? are you a manual car?

I would definitely like to find out why there is no additional air intake on your box

Sorry that is not cool at all

Sorry, i didn't take a picture. My car is 6MT. I pulled out the whole lower box to make sure and there was nothing except for the fender intake hole. Oh well. Im just gonna have to drop in a K&N.

[40valve]

Don't worry poopypants, you are not the only one. Mine doesn't have it either.

[iconoclast]

i tried this mod a lil bit ago and there is no such opening. Mine is an 04 S4, so i would think this only applies to the 05's. The only intakes are the ram air from the front and the side fender. Oh well, at least i tried.

2nd.

[Justincredible]

WOW ok. Well I tryed to find out more info on this guys. NONE available so let me ask you

Are you guys all Manual cars and are all of you 04's

Thanks guys let me know so I can update the thread

[40valve]

I'm manual and it's a really early '04. Production date is 12-16-2003.

[V8S4Fun]

I definately have one, haven't removed it yet though

[cabracco85]

What did you do with the little filter that connects the air duct on the top of the airbox? did you just throw it out or did you leave it in there. Mine was all torn up so i left it out.

[cam]

changed out the air and cabin filters on the s today, i took the valve out and capped the line, havent really noticed a difference, but ive only driven the car about 2 miles.

[Beelzeebub]

so let me get this straight...the flap only opens when rpms hit 5k or more? and it does not open at all when below 5000 rpm? and this applies to Tips and Manual transmissions?

[Justincredible]

changed out the air and cabin filters on the s today, i took the valve out and capped the line, havent really noticed a difference, but ive only driven the car about 2 miles.

You are really only going to feel the extra power (if you can call it that) when the car needs it. So for average driving there is not going to be much of a marked improvement. There are areas in the rev range that it will be more stated.

so let me get this straight...the flap only opens when rpms hit 5k or more? and it does not open at all when below 5000 rpm? and this applies to Tips and Manual transmissions?

The flap is completely closed under 5k with the 04 guys at this time it seems there might not be one. This MAY be one of the reasons why so many 04 guys say they like the open element and feel there is a improvement

What did you do with the little filter that connects the air duct on the top of the airbox? did you just throw it out or did you leave it in there. Mine was all torn up so i left it out.

Ya just throw it away. If you are not real maintenance oriented where you are going to check your Air Filter 20,000 miles then you might want to think about keeping it. But I found there was more of a restriction there because of all the junk that was cought in it. I know that stopped the junk from going into the air box but there there is also the filter that is there so. I would say just take it out

[cabracco85]

Did this mod today, my impression are i can feel a difference, but that could be from all of the crap that was in the airbox and that little screen. I couldnt beileve how much garbage came out of it,there was probally 3lbs of junk in the airbox and screen. I also need to get a new filter but ill do that in the morning since it is too late tonight to get a new one. This is a pretty easy way to free up a little power. I also noticed that the transition when you hit 5k is not like before but alot smoother. It still pulls as hard but not like all at once like before when that valve opened. Thanks for sharing this with all of us. BTW has anyone tried to drill holes in the side of their airbox to see if that would help. Like the side that faces the passanger fender and the side that faces the front of the car?

[Beelzeebub]

i may have missed it somewhere in the posts but does doing this mod adversely affect the MAF or the OBD? Will it start throwing error codes left and right?

[Captain Insano]

WOW ok. Well I tryed to find out more info on this guys. NONE available so let me ask you

Are you guys all Manual cars and are all of you 04's

Thanks guys let me know so I can update the thread

Anybody else find out if they don't have the flap with a MY04? I have a MY04 Avant MT and was wondering.

[poopypants]

i may have missed it somewhere in the posts but does doing this mod adversely affect the MAF or the OBD? Will it start throwing error codes left and right?

I would highly doubt it unless you remove the filter. Usually the ECU adjusts to the higher volume of air that is being used.

[Justincredible]

There is a 0% chance that the car will get a CEL of MAF issue because of this. the GPS in the maf goes up but the car tunes it self off the MAF readings.

I actually tested the MAF air pass to see if you can get a code. You can pull out the Air filter and still not get a code. put a leaf blower in front of it and you will get code. : )

[FTYAVANT]

Did this mod about 2 months ago...replaced air filter with K/N and removed the fender tube "straw"...makes a tiny bit more noise and has increased throttle response a bit. I suggest it just based on the better throttle response!! Cant wait to get this exhaust done.

[cabracco85]

There is a 0% chance that the car will get a CEL of MAF issue because of this. the GPS in the maf goes up but the car tunes it self off the MAF readings.

I actually tested the MAF air pass to see if you can get a code. You can pull out the Air filter and still not get a code. put a leaf blower in front of it and you will get code. : )

How long does it take to adapt, instant or is it like when you chip a car and it takes a few cold starts. I ask because i put in the k&n filter and it seems like i might of lost some torque. Im not sure if i did or not. But yesterday when i had the stock filter in it felt like it didnt loose any torque but the filter was really dirty. Do you think that now it is actually getting more air that the car has to adapt to new found air, or would the adaption be instant. Im pretty sure i know the answer but i wont to get some insight from others.

[jaybquick@JHM]

How long does it take to adapt, instant or is it like when you chip a car and it takes a few cold starts. I ask because i put in the k&n filter and it seems like i might of lost some torque. Im not sure if i did or not. But yesterday when i had the stock filter in it felt like it didnt loose any torque but the filter was really dirty. Do you think that now it is actually getting more air that the car has to adapt to new found air, or would the adaption be instant. Im pretty sure i know the answer but i wont to get some insight from others.

Should adapt instantaneously since the GPs will change it just responds accordingly. Same concept as driving into higher altitude, the GPs drop due to thinner air and the car automatically sees less air so it supplies less fuel and keeps the mixture righ. That is one of the cool things about a car that depends on a MAF sensor. Very mod friendly setup unless you go way out of spec, usually 20% or more. This is not gonna happen unless you did some serious engine work like head porting cams, etc.

However just in case you can unhook your battery for about a minute. That will force it to start fresh.









BTW. I did some reserach in ETKA and cannot find any airbox part numbers that weren't missing the part you are having them mod. I even looked at German S4s as early as 03. I looked in 4 different countries for variations. None were found. They all show they have that port. Who knows though they apparently threw something on the early production models before they finalized the car or something. Interesting huh.

[cabracco85]

Should adapt instantaneously since the GPs will change it just responds accordingly. Same concept as driving into higher altitude, the GPs drop due to thinner air and the car automatically sees less air so it supplies less fuel and keeps the mixture righ. That is one of the cool things about a car that depends on a MAF sensor. Very mod friendly setup unless you go way out of spec, usually 20% or more. This is not gonna happen unless you did some serious engine work like head porting cams, etc.

However just in case you can unhook your battery for about a minute. That will force it to start fresh.

.

Thats what i was thinking but i wantd to make sure it didnt have to adapt like when you chip some cars. But it seems to be a little better today on the torque that i thought i lost. I hope tomorrow the track will be open so i can see what the car will run

[sayporsha]

Sounds good, I think I'll try it. I had a Porsche 968 & did an airbox mod that was good for an honest 10 HP increase.

How close to the ground does that ram air tube go? If you open it up & drive thru deep water you could suck water & destroy your engine. Not saying it's a certainty, just a possibility.

[jaybquick@JHM]

Sounds good, I think I'll try it. I had a Porsche 968 & did an airbox mod that was good for an honest 10 HP increase.

How close to the ground does that ram air tube go? If you open it up & drive thru deep water you could suck water & destroy your engine. Not saying it's a certainty, just a possibility.

The inlet is above the passenger side foglight and drops down from the top of the auxilary radiator. So it is pretty high.

[NYCS4Avant]

The inlet is above the passenger side foglight and drops down from the top of the auxilary radiator. So it is pretty high.

Does anyone have any pictures of the inlet track? I'd be interested in looking into the possibility of a DIY ram intake upgrade. Coming from the Volvo scene, particularly the P2 S60R's, many enthusiasts did this:







The original "inventor" did similar tests to the original poster and found that it eliminated the vacuum conditions in the stock airbox. For those of you with time or interest, the full thread explains the benefits and shows the tests. It also has pictures of what the volvo crowd called "the snow valve" that was removed to attach the hose. Full thread:
http://forums.swedespeed.com/zerothread?id=55492

These could definitely help keep the whole DIY clean and make the front scoop useable. :

[jaybquick@JHM]

We have been looking into making a ram air kit as well. Except if you look there is hardly any room so we will have to build some kind of unique or flat piping to get it up and over that aux radiator.

It is on our current long list of new products to build and look into.