Air Intake

Mod Benefit Drawback Is it a problem? Notes
Replacement performance panel air filter
e.g. K & N
  • Improve turbo spool up time
  • Improve air flow into engine
  • More power
  • Probably will never need to buy another air filter!
  • Less restrictive
  • Need to wash it out and maybe oil it now and again


Don't get a foam filter as these are generally poor at filtration and if they disintegrate it'll disappear into your turbo and engine

Remove intake resonator
  • Less pipe work, crap, complexity and weight
  • More room in the engine bay area/wheel arch
  • Meant to be a noise reducer but I found very little difference!


May provide enough space for:
  • WI reservoir tank
  • Cold air feed to air filter
Straight air intake and large cone filter
  • Stock air box and ribbed air feed pipe to turbo restrictive and in the way
  • Improve turbo performance and spool up time
  • Less crap in the car
  • More power
  • More efficient
  • Bit tricky to do
  • Draw hot air from engine bay into engine - bad
  • Need to make cold air box
  • Need to buy or fabricate adaptors for idle up and PCV breather hoses
  • Need to extend the AFM wiring loom
  • Need an air filter to AFM adaptor plate


ish - takes time/effort

Several companies manufacture cone air filters. A K&N is fitted at the moment but another alternative is the A'pexi filter which has proven to filter and flow wellBlitz make a shiny stainless steel mesh filter - you can see through the filter, so it doesn't filter very well!
Cold air box
  • Feed the air filter with colder air
  • Reduce intake temps ~2oC
  • Helps to prevent detonation
  • More power
  • Needs fabrication and fitting

ish - takes time/effort

Gas flow AFM
Stock AFM Pictures
  • Provide a smoother and greater air flow through the AFM to the turbo
  • More power
  • Need a Dremel or equivalent to do the porting

ish - takes time and effort

I "think" that made a small difference...
PCV catch can
  • Prevent oil mist from entering the air intake
  • Ensure IC operates efficiency
  • Stop coating everything in oil
  • Stop burning oil
  • Help to prevent detonation
  • Requires fabricating or to buy
  • Make sure it is internally baffled


ish if fabricating, No if buying!

The GReddy catch can seems to be a good unit. The Mocal one is rubbish as this is not internally baffled. The Halfords can is better than nothing but not brilliant...(it's cheap!)
Port intake manifold
  • Increase power
  • Reduce intake restrictions
  • More power
  • Turbo spools earlier
  • Need to remove manifold very awkward if engine still in car, but can be done

Yes, very awkward

Awkward to remove the manifold Need a Dremel or something similar to do the porting. You can pick something similar up for <20 Sanding drums are available and shift aluminium in no time
Remove & port TVIS
  • Increase power
  • Reduce intake restrictions
  • Less complexity
  • More room around rear of intake manifold
  • Turbo spools earlier
  • Have to remove manifold - very awkward with engine in car but possible!
  • Fabricating - need to plug various holes, drilling and tapping required
  • Porting takes time and effort
  • Due to lower port velocities i.e. air doesn't travel as fast in the intake runners idling is sometimes a little low when in traffic ~500 rpm

Yes - access very awkward

Low idle speed produces a low oil pressure which is bad. Mr bearing is not protected as well from damage by Mr crank...When the car is hot in summer and stuck in traffic it very occasionally stalls due to the low port velocity
Bored out and gas flowed Throttle Body
  • Increase power
  • Reduce intake restrictions
  • Specialist machine shop required


Difficult to ascertain it's benefits as this was fitted with a few other mods at the same time. The 205 came with a larger throttle body 60mm vs 55mm for 165 and 185
Tighten AFM
  • To reduce over fuelling, especially if running a larger turbo
  • Increase output power
  • Increase fuel economy
  • Reducing the spring tension will allow air entering the engine an easier path
  • May run lean - bad!

ish. Make sure the car is not running lean

Try a 1 or 2 notch increase in spring tension

I have seen an increase of ~20bhp on running a 44mm trim turbo just by altering the AFR to closer to 12.5:1

Front grille
  • Improve air flow to air filter
  • Provide more cold air to intake
  • Need to cut/drill the grille


Drilling holes in the grille below the lhs headlight will allow more cooler air to enter into the air filter area
Cold Air Intake
  • Improve air flow to air filter
  • Provide more cold air to intake
  • None


Try running a length of hose front the front bumper back and up where the intake resonator used to be and out just by the air filter. Note this is the stock air intake path...