W210 airbox modification thread

[m1tch]

Hi all,

I have decided to post up a thread which will be more of a R&D experiment with my E300 project. I am going to be doing modifications to the stock airbox on my W210 to see what the differences are with different setups and the best route for any performance gains over and above the stock setup.

Firstly here are some specs on the stock setup - basically everything feeding into the turbo:

• Airbox overall is very large, unfiltered air enters the bottom of the air box, through the filter then through the pipework to the turbo via the top of the air box.
  
• The MAF is connected to the airbox via a rigid pipe - its a large 3" pipe diameter
  
• The MAF pipe inside the top of the airbox has radius bends like a velocity stack for smooth airflow
  
• The pipe between the MAF goes from the 3" (78mm) to 60mm which connects onto the turbo
  
• There is a crank case breather line attached just after the MAF introducing oily fumes into the inlet
  
• The bottom of the airbox is a round 3.5" intake
  
• This is then attached to a small 90 degree connector into the front facing air intake
  
• The air intake slot is front facing, between the headlight and the radiator - it is rectangular and around 2.5" by around 4"
  
• The front facing air intake sits behind the the bonnet next to the grill (but not actually behind the grill)
  
• There is probably around 1-2" gap between the front of the bonnet and the air intake

Here are my comments on what is good about this setup:

• The stock airbox should be large enough to accommodate quite a bit of power
• The MAF is large and has a good radius for flow
• The large 3.5" inlet should be able to supply the engine with plenty of air to the bottom of the airbox
• The airbox is well situated away as far away from the exhaust tucked into the wing

Here are my comments on what could be improved:

• The pipework from the airbox could be improved as it is corrugated rubber
• The front facing air intake is a restriction - the WHOLE engine is breathing through a 2" X 4" hole
• Vented crankcase gasses could interfere with the air flow

Here is the issue I have with the front facing air intake:

To get to the airbox the air must:

• Hit the front of the car and go through the grill
• Go around a 90 degree bend to the front of the intake between the back of the bonnet and the front of the radiator (bonnet blocks direct flow)
• Go around another 90 degree bend into the small rectangular slot
• Drop down 90 degrees down the back of the headlight
• Turn another 90 degrees into the plastic elbow at the bottom of the airbox

I have just gone out and simply removed the small 90 degree plastic piece between the front facing air intake and the bottom of the air box, I have just test driven it and this is what I have found:

• Increased throttle response - no lag in pressing the throttle and movement unlike before (eg pulling out of junctions)
• Smoother changes in gear
• Smoother idle
• No real increase in induction noise around town or on the motorway
• Better low down torque - power feels more linear rather than sudden
• Boost pressure builds more predictably

Please be aware that the whole engine is bone stock, it is running a new PAPER air filter which again highlights how the drop in 'performance' air filters aren't necessarily going to give increases in performance.

This is just an initial test, I will get up some photos soon for everyone to comment, so far its cost me nothing and I have performance gains. I am aware that the engine will be sucking in slightly warmer air, however the stock air box is well out of the way and there is plenty of air flow around that side of the engine bay. I have also kept the stock front facing air intake so that would also supply some fresher air towards the intake area. The bottom of the stock airbox actually sits on the side of the engine bay and is shielded from any water from the road.

Here are a few things I am thinking about testing out:

• Larger cold air intake replacing the stock intake to sit between the radiator and headlight
• Hard pipe between MAF and turbo
• Catch tank for oil fumes from crankcase
• Metallic tape on the engine side of the air box to reflect heat
  [*}Possible additional air feeds to the side of the airbox

I might also try:

• Drop in 'performance' air filter
• Cone filter sitting inside the stock air box
• Enclosed filter replacing stock air box