Drilled Airbox

[HandsomeRob]

Right well, to begin at the beginning.

Going back a few years to my yoof and monthly purchase of Max Power, an open cone induction kit was the way to go, be it the cone filter type, mushroom foam, whatever. The general consensus was that whilst it made a lovely irritating noise and all that, the general argument ended up revolving around airflow increase vs hot air intake.

Anyone who has a fair amount of commercial business sense will tell you that any mass produced automotive part (specifically an airbox) is fundamentally a compromise between airflow, performance and cost. A final contributory factor would be noise & comfort. For this reason as we know, Volvo airboxes are made of good quality material, lots of foam dampening inside, and a lengthy cold air intake along with the hot air intake too.

From a performance aspect therefore, we (and I) used to have two options: Use an expensive enclosed induction cone system, or simply drill/cut a large space into the bottom of the airbox & sides facing the front and wing.

Now considering doing this to the T4 together with a performance panel filter, and my rambling head can think of no rational reasons why not to....

Thoughts?

R

[motormadfrosty]

I am going to watch this thread with interest. When I purchased my T4, it had a universal cone filter and I have got to admit, I loved the noise, sounded almost like a dump valve on lift off, but put my sensible head on and convinced myself that the standard box and filter would make it run better. To be honest, performance feels the same but I REALLY miss the noise.

[Nikdev]

Just drill it, but make sure it don`t just sucks hot air

[scoobysn7x]

Originally Posted by Nikdev

Just drill it, but make sure it don`t just sucks hot air

was just about to post this, the hot air getting sucked in may have an adverse effect, maybe drill a big hole in the bottom and put a cold air feed (piping) down by the fog light

[m1tch1987]

I would suggest drilling the air box (but make sure its the right side!) but also think about a cold air duct aimed towards the box, the OEM airbox does a good job at being a heat shield and not allowing hot engine bay gasses into the induction pipes etc

Although as its a T4, its turboed and intercooled, so cold air is good, but its going to be getting very hot as its compressed by the turbo, so perhaps think about upgrading the IC if cooler air is what you are wanting!

[HandsomeRob]

Well, patience is a virtue blah blah blah - dinner can wait so I've been pottering outside

Took the airbox off and had a look. A few observations:
* There is a cold air feed (I use the term loosely) coming from the front wing.
* There is a buggerload of sound-insulating foam.
* Most intriguing of all, there is also what I initially thought was a resonator box attached. Turns out that it is a..... not a ****ing clue:



The round hole is capped. Therefore, no idea other than to increase the internal volume and it was easier to mould it that way.

So I kept the 'add on box' off, and also tore out the foam innards. Took it for a drive and the result is minimal, but noticeable. Upon flooring the throttle, noise is definitely louder and deeper. Driving response appears brisker, somewhere between subconscious and placebo.

As you can see, the frontal gap faces the battery, so while it may improve general accessibility for air, a cold air feed would do wonders. Now debating tearing larger chunks out of the bottom and side.....

[960kg]

.....this was a common mod. on the 850 T5....i did it to mine and the holes are 10mm with as many as possible without being detrimental to the strength or support of the airbox.....the warm air does not really exist to that degree as the drought will come up from the gaps around gearbox end that`s if it is the same construction underneath the airbox as the T5, i would check this first as on the T5 there is a large gap under it, the T4 i can`t remember??.....while your at it if your worried about more heat that you don`t want move the horns as they impead the airflow to the intercooler, put them under the bumper somewhere......

[tommy t4]

does sound good about being a heat shield and that, but dont you think its a bit of a "bodge job", and will the charged gases be geting away quick enough no that the standard re circ has gone?

[twinturbo]

I drilled an airbox on a car 15 years ago, and another one I have came with it drilled. Does make a deeper note.

Interestingly, I was reading (a few weeks back) a technical release manual for a popular 1990's mid sized family car. It had 3 resonators, one of which stretched over the inner arch! they had obviously spent a lot of time tuning the inlet tract. I wonder how much that detracts from the power, or do the pressure waves help.

TT

[Volvon]

Cold air = denser = more fuel required
warm air = more volume = less fuel required

If you can live with 20MPG, pull the warm air pipe off that comes from the manifold into the lower airbox and drill a few holes. This should replicate cone filter performance levels.