Toyota Celica GT4 ST165 air intake modifications

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	No	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 Picture	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!	No	May provide enough space for: WI reservoir tank Cold air feed to air filter
Straight air intake and large cone filter Picture	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 Picture	Feed the air filter with colder air Reduce intake temps ~2^oC 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 Article	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 Ł 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 <Ł20 Sanding drums are available and shift aluminium in no time
Remove & port TVIS Article	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 Article	Increase power Reduce intake restrictions	Specialist machine shop required Ł	No	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 spring	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 Article	Improve air flow to air filter Provide more cold air to intake	Need to cut/drill the grille	No	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	No	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...