I’ve been looking over my 3.0L study guide and I stumbled onto something very interesting that I thought I would throw out there to share.
The B6 A4 has a larger intake by 50% then previous years. So the air box it self should be more then able to handle the power. How ever when looking deeper into the information available it seems there might be a indication of a restriction.
Look this picture over and please share your thoughts.
http://audirevolution.net/addons/albums/images/862433931.jpg
I dont recall seeing an intake from the wheel well, may have to have a dig around. The A4 also has a few less intakes than the S4, would upgrading the airbox to S4 increase the amount of air we can get in the engine.
Would the dampner be causing a restriction on the airflow speed and amount of air getting in the engine. If we removed this would it create a better flow, not really sure how it exactly works (I mean who really cares what the intake noise is at that sort of engine speed)
Cool. I will grab some pics when I can
Hmmm, I thought I had some pics of that wheel well air intake from my s/c install, but I think I was taking them on Jay’s camera then, not mine. But the airbox on the B6 A4 looks identical to the early B6 S4 airbox (the early S4’s didn’t have the “ram” air inlet from behind the aux radiator like the majority of the S4’s have).
In order to catch a glimpse at that wheel air inlet, I believe you have to pull the vender liner, or when you change your air filter you should be able to see the hole through the fender with the plastic tubing. It’s a pretty cool design, but I dunno how “really” useful it is.
On to restrictions:
First off, I know JHM mad the silicon MAF boot to replace the ribbed section. It’s not a huge deal, but it could be a small piece to the puzzle, however with the S4’s larger throttle bodies and different design, that part isn’t one that you guys can just swap over. Just noting though that the ribbed tubing ins’t the best for performance. You may be able to pick up a plain silicon hose those and swap in, depends on the bends I guess.
Secondly, to me, it looks like the inlet right before the throttle body is a pretty sharp turn. I would think that surely isn’t helping airflow. If the 3.0 ever gets around to adapting a larger throttle body, it would be nice to take some of that bend out of the system.
Finally, the easiest and probably most restrictive part is the “helmholtz resonator”. Anything a car manufacture ever puts into the car to decrease noise or increase emission efficiency (i.e. precats, which are a law now), secondary air pump, etc are certainly going to hurt performance. I haven’t ever really stuck my head around a 3.0 motor, but it would be good if some of you all could look at that resonator and figure out how it works and if it could be bypassed/removed. I would think that wouldn’t be a big task, and could certainly open up some midrange and high rpm hp, it would just be interesting to know if it’s a full vacuum system, or if it’s electronic at all (i.e. will it throw any codes without being tuned for). Also, removing it may give more room to remove that sharp angle into the throttle body.
Edit: Just trying to get a better idea for the “helmholts resonator”. Is this picture what we’re (or moreso I) am talking about. I just don’t really know and would love some more information/insight. Does the resonator tie into those vacuum pipes off the throttle body, or is it more integrated then that? I just am not too sure what I’m looking at or where that part is exactly.
http://audirevolution.net/addons/albums/images/235809697.jpg
http://audirevolution.net/addons/albums/images/304834187.jpg
wow great info… it literally says twice that the intake was designed to limit performance…
Cheap things to do, disconnect the vac line that opens the helmholtz resonator. You could remove the whole resonator, but removing and capping the vac line should hopefully keep the flap closed. If it doesn’t break it off and JB weld over the hole.
Take off the front bumper and fender liner and spin the fender inlet piece to face forwards. I know Count on here advised me to do the same on my S4. If you don’t want to spin it, then I’d block off the inlet since it’s limiting the effectiveness of the airbox.
Make a ram duct from the passenger fog grill straight into the bottom of the airbox. If you don’t have the AUX radiators like the S4 it should be very easy to route.
Great posts.
Beemercer you said that the wheel intake reduces velocity and speed. Im not the biggest on math terms. Is this to say that the mass or amount of air is getting blocked off or disturbed is enough to eliminate some of the RAM air effect?
The resonator looks like that could be a good thing to remove.
Also maddog good spotting the quick turn on the inlet. That could help some if it was a smoother transition.
yes essentially, it negates a lot of the beit to having the air scoop over the radiator. Ram air is kind of a funny. phenomena in that its always thought that it increase air pressure in the airbox but it seems its more about increasing air charge velocity to almost externally compress the air charge as it hits the back of the valves. Food for thought on the ram air, if you wanted to increase the pressure of the air with a cone it should look like this:
-air-> <cone
not
-air-> >cone
so the funneled cone shape you see a lot, tapering from larger to smaller will actually decrease air pressure but increase velocity
Well I see Im not needed here. Beemercer great job as usual.
I found this issue out a while ago and as beemercer said I found that a quick fix for this was to change the direction of the WHI (wheel housing intake) This was hard to gauge how much or how little it actually effected the performance. While we did see a higher MAF reading Im not so sure that closing off the WHI would have been a bad idea.
Im under the thought that, If we have ONE major inlet and no other sources of air that the air box will be more likely to pressurize. I look at this like the more inlets we have the more likely the air box is to loose pressure due to the weaker stream.
I never got a good chance to test this. I had justincredible test this on one of the RS4’s he was helping a guy with. Sort term data supports closing off the other sources of air and going with one dominate large intake.
Thought I would throw up some pics of the wheel well intake
http://audirevolution.net/addons/albums/images/875587917.jpg
http://audirevolution.net/addons/albums/images/752959679.jpg
http://audirevolution.net/addons/albums/images/844972715.jpg
I was just wondering if we should be using the K&N drop in filters?
I was told the oil on them is not good for the MAF sensor and that they come pre oiled. And if thats true then I don’t see why we can’t use them and just clean it first and then never use the oil.
I know this is late but needed to be addressed.
The problem I see with the K&N drop in oil filter is that people clean them re-oil them and drive the car immediately after. The excess oil is not absorbed and has no place to go but clog the MAF sensor.
I believe the second intake/wheel housing intake is not really for getting extra air to the engine.
Its more for water evaporation when the car takes in any water when you drive in the rain.
The air box wheel housing intake has a cross flow of air to dry the extra water up after it collects.
Or if the main intake collects too much it has a place to go besides into the engine.
That’s why most of the air ducts before the MAF are ribbed. To help keep large amounts of water from going into the engine.
I think 2 years is a bit past late. I don’t even remember posting that. Personally I never use K&N filters. I stick to genuine Audi they filter much better. I’d rather have cleaner air than more air. And from what I was told your never supposed to use the oil if you are using K&N filter on our cars. I’m pretty sure the second intakes function is like it says in the diagram from Audi which is to reduce intake speed.
Yes, it is used as a baffle to regulate air into the engine. Like most parts on an Audi.
Lets play what if.
What if it had a second function?
Where does the water go when it rains and Your driving into a downpour?
I know it doesn’t take on that much water. But.
Does Your engine just eat the water?
Short answer, Absolutely.
Not sure where you live Halo, but if you live in a climate that gets cool and humid, ever notice how you can sometimes see the exhaust even though the air is not below freezing? While this could be because your car is burning oil :o, chances are this is because the complete combustion of hydrocarbons results in CO2 and water in the form of steam, not to mention other byproducts, some of which are caused by the additives in the gas.
Anyways, when the air is humid, or raining for that matter, all that moisture is pulled into the intake. When it gets to the filter the water vapor in the air passes through the filter along with the air, enters the engine, and comes out the exhaust as steam. When rain droplets get to the filter on the other hand, they are “caught” and absorbed. As the air passes through it picks up small amounts of the water as vapour, much the same as a cool humidifier does, and it passes through the engine harmlessly. The more filter that is there the more moisture that can be absorbed before actual drops come out the other side.
Long story short, when it comes to engines, water vapour is generally harmless under normal conditions. Water in liquid form on the other hand, even just drops of it, is destructive.
Back to the whole second air intake, I tend to agree with A43Go6Mt on this one. While it will help the filter dry faster when the engine is not running, I highly doubt that it is the main reason for it.
Just my 2 cents.
I saw, and replied to a similar thread on AZ. BTW, my first post here 
Regrading this statement from SSP_255, 3.0L self study guide:
The intake noise is damped by a Helmholtz resonator.
The intake resonator is not a silencer and is not designed to make the car more appealing to soccer moms. Noise means more than just an audible signal. In electronics, noise is unwanted random addition to a signal. In the intake system, noise is unwanted addition to laminar flow. Sound waves travel through ___ (fill in the blank). If you said “air”, you are correct. When the intake valves close, the air bounces off of of the valves (see explanation below) and creates a “ping”. That ping is noise, unwanted addition to laminar flow. The helmholtz resonator reflects the ping and actually boosts the input of air into the next cylinder in the firing order by increasing the velocity as the intake valve opens. This is due to the frequency at which it operates. The ping from the previous intake valve close is timed to pong the next intake valve opening in order to ensure that there is no dead air space in the manifold. Sound reduction is a side effect.
My response on AZ:
First off, I applaud “out of the box thinking.” Innovation comes from challenging the Status Quo.
Now, here is why I would not change my air intake in this manner however:
The air intake system on our Audi’s has been designed to deliver the most efficient method of getting air into the cylinder. It is designed and tested using some of the most advanced tools available. These tools have been developed specifically for measuring the effects of airflow from the leading edge of the air intake all of the way to the lip of the intake valve(s).
The most efficient delivery of air is laminar. Laminar flow essentially means that the air moves directly through the system with the least amount of turbulence. We want the outside cold air to move through the system and into the combustion chamber as quickly as possible so we can take advantage of the cooler oxygen rich environment that this air provides. Turbulence in the air intake reduces air flow as it creates opposing forces that fight against the direct flow of air. This turbulent air can gain heat as it continually comes in contact with the warm walls of the intake. Turbulence also causes fluctuations in the mass of the air.
Why is air mass fluctuation bad? The air mass is measured by the MAF and is used by the ECU to balance and deliver the correct air/fuel ratio to the engine. These are closed loop systems and the O2 sensor checks to see if the ECU made the right air/fuel mix decision. If the system is stable, that is the air mass doesn’t fluctuate, the measurement, adjustment and testing would plot to a smooth curve. The air mass measured is the same as it gets to the combustion chamber and the air/fuel mixture is correct. If the air mass is constantly fluctuating, then the system is constantly making corrections and a plot would look like a series of wild peaks and valleys as it constantly tries to measure and correct itself. The fluctuations cause the wrong air/fuel mixture to be delivered to the combustion chamber.
There are two things that can have an adverse effect on the air intake and create air mass fluctuation. These are Air buffeting and Resonance.
Air buffeting is something that I think most of us are familiar with. Roll down your window or open the sun roof at certain speeds and the cyclic pressure of the air passing over the opening creates an air hammer effect. How do we solve that problem? Well, we could say f’ it and close the window or sun roof, or we partially open another window, right? The pressure equalizes and our ears eventually stop bleeding. The same thing happens with the opening of the air intake. Air passing over the entrance to the air inlet creates a cyclic pressure differential and the air mass constantly fluctuates. How is this problem solved? The same way that we solve it in the passenger area, we create another opening that helps to equalize the pressure. Just before the air filter, another opening allows air to slowly bleed off through the fender well. This allows the pressure inside the intake tube to equalize and stop the buffeting. In turn this helps to create a laminar flow along the airs path to the intake manifold. As air passes the MAF the air mass is stable and information sent to the ECU can then set the correct air/fuel mixture to hit the cylinder at the right time due to the laminar flow of air. I think blocking off the equalizer opening into the wheel well makes the MAF’s ears bleed.
Resonance. Resonance is caused by the pulsing draw of air into the engine. The engine doesn’t draw air steadily like a vacuum cleaner. Each cylinder only draws air 1/4th of the time and this is during the intake stroke. While the cylinder is drawing the air it also isn’t at a steady rate. At top dead center (TDC), the piston stops, changes direction, the intake valves open and the air is drawn in. As the piston reaches for bottom dead center (BDC) it moves faster through the stroke so the intake is progressive. At BDC the intake valve(s) close. Suddenly, all of the air that was rushing past those valves is stopped and the air around those valves bounces back in the opposite direction. Remember, for every action there is an equal and opposite reaction. That pressure wave can travel all of the way back through the air intake system and cause turbulence. How can we absorb that shock wave so we don’t interrupt the flow of air for the next cylinder? By installing a resonator just before the throttle body. A helmholtz resonator to be exact. The pressure wave moving in the opposite direction of flow tries to ram air into the neck of the resonator. The pressure inside the cavity increases and the air bounces out equalizing the pressure and keeps the wave from disrupting the laminar flow. In ricer terms, removing the intake resonator makes their cars “growl” and the sound is always more important than horsepower or fuel economy.
Your results may vary. Opposing view points welcome. Additional pepperoni available upon request.
Where I mention “we create another opening that helps to equalize the pressure” , I meant that the engineers have already created the opening to the wheel well just before the filter box. it exists on the stock A4 B6 3.0L setup already.
In the last paragraph I mentioned “By installing a resonator just before the throttle body.”, and again, that exists on the stock A4 B6 3.0L setup already.
To summarize, the best setup for performance , IMHO, is to leave the stock air intake system alone for a NA A4 B6 3.0L. Once we all get a Supercharger to bolt on in the future then we may need to rethink it
Wow, great post 4g. You just made me rethink a lot of what I’ve heard and done on not just the a4 but also previous vehicles. I’m definitely contemplating putting the intake back to stock now.
Great post factually wrong…
So far its been proven that blocking off the air box makes more power and that removeing the rez will help flow.
Actually comonsence will tell you that. Anything that impeds with the flow of air is going to cause a loss of power. While opening up a window might help create a different pressure zone in the cabon… the idea and working of RAM AIR is simple. Get the strightest shot of air from the outside to the throttle body. No turns no disturbence. Helmholtz creates disturbence in the flow. It impeeds with the pulse of the motor bringing in air by having a break in the air flow. The Gelmholtz actual job is to create turblience to break up the noise… Its clear remove it from your car you will now hear the intake being louder…why more un interupted air flow.
If what 4g was saying was true it would be on more sport models…and its not… Its only on things like the 3.0 and the A8 cars where they wanted to quiet down the noise.
It dosen’t matter what any of us say. Audi uses and classified the part by calling it a noise damping system.
The intake noise is damped by a Helmholtz resonator… The fact that Audi went out of the way to let us know they put the helmholtz on there to dampen the noise is because they put it on there to dampen the noise…you dampen noise by disturbing the air flow that carrys the noise.
Fact Audi didn’t make the best design for flow of the air… they tell us that and thats why you block off the air box and remove the helmoholtz…
I hate to say this… but while 4g made a great first post it was wrong…check the performance increase to back up the known theory…As to not argue… if any of what he said was true…why is it not on the S4 RS4 S5 RS5 R8… The helmholtz creates a disturbence in flow… You want high pressure not equalized pressure on top of your thorttle body. The entire point he made was mute… IF that was true no one would make a ram air. If that was true no one would gain any power with an open element… Great post… juts not mechanically factual on the performacne side…
What I would add to that is the intake manifold is rigid for a reason. To give the Helmholtz resonator the best chance to minimize the air bounce of the back of the closed valves.
Also the ribbed flex pipe at the front of the engine bay is to help draw water out of the flow of air.
So it doesn’t go right into the motor.
Edit.
Yes, lets just ram air straight into the MAF and throttle body and we will see a power increase.
That works great on cars that don’t have multi valve timing. Last time I checked Audis have multi valve timing.
and if you missed my post. Here is audi saying this is how it works.
http://audirevolution.net/addons/albums/images/862433931.jpg
Ok chris, so if I understand correctly, the general consensus from those who have be playing with the intake for a while now is that the most power is developed when fender intake is closed/blocked and res is removed and blocked.
Now I put forward a question. Currently my setup is, stock intake with blocked fender intake, res removed, gutted cats, 2.5 magnaflow catback and JHM tune. I just recently did all these upgrades and, while the car has a noticeable increase in power across the spectrum, i’m now having stalling issues and fyi its an auto. While keeping rpms above roughly 1500 I’ve had no problems, but I’ve found that once in a while driving around town at slow speeds, and generally it seems to happen most while slowly accelerating from a stop, the throttle stops responding. It’s almost as though its being choked off, rpms just drop right off, sometimes the engine dies completely and sometimes its only a momentary lapse. Hooking up VCDS I have no engine codes thrown so I’m kinda at a loss. I’ve been pondering swaping the ecu back out just to confirm the error is not in the ecu itself, but after reading this thread the other day I started to wonder if, with that fender intake blocked, the engine is not able to draw enough air in while at a standstill.
So I guess my question is, have you or anyone else ran into this issues while doing some upgrades?