customising a standard factory fitted air box ( is it poss to do so?????)

[locin78]

I have a standard mk3 gti 16v is it poss to customise the standard air box the car came with for more BHP??

[shepgti]

2 secs of searching brings up this http://forums.vwvortex.com/zerothread?id=3063843 

[locin78]

thank's

[Ess_Three]

I have a standard mk3 gti 16v is it poss to customise the standard air box the car came with for more BHP??

You can modify it, sure.

But how you do it, depends on whether you want it to sound better, or add more power.

Drill holes in it and let the hot air in from the engine bay...and you are more likely to loose power, than make any.
This is common sense and has been proven many times. To some, it sounds good though.

If you want better performance, you need to increase the internal volume so the engine has more air available when you snap the throttle open, make sure the internal air stays coolr, and feed the inlet with as much cold air as you can. Adding a K&N panel filter adds a small bit too.


Take the silly snorkel thing out for a start:




..and smooth off the edge where the air flows from the airbox to the inlet hose, using a Dremmel.






Remove all the hot air feed gubbins (hot air feed from the exhaust manifold). You don't need it. You don't live in the Arctic.
Remove it all, remove the nylon lines that go to the TB, and plug them up at the TB.

With the gubbins revoved you need to blank off the hols that would otherwise let hot air in...tape it up, plug it with something...do what you want. Just seal it.

Then work out how to get more cold air in:
Remove and bin the wing fed small inlet duct thingy.



I ended up with a 3" subwoofer port araldited into my airbox, which site hard up against the back of my Hellas...so lets far more cod air in than the standard wing inlet ever did.

This way, you end up with cold air from the front, and more of it...smoothed to give better flow (not hot air from the engine bay) and if you add a K&N panel filter you will see about 3-4 BHP repeatable on the Dyno.

That's proper power gains (not much...but nothing ever does despite the ludicrous power claims) up at the top of the revs due to better breathing, better throttle response and a bit more noise.

That's how i've best found modifying the airbox to work...after 8 years of trying many different inlets, cone filters, CAIs etc...this one still works the best.


Or you can drill it and let hot air in.

[Petec82]

That is really useful information ess_three and a really good set of instructions. It seems to be a more well thought out approach than turning the standard turn box into Swiss cheese approach. This should get stickied or something!
Pete

[Ess_Three]

You will always get more power with lots of COLD, dense air.

HOT air reduced power...that's proven.

Swiss cheese the airbox and log the values from the IAT sensor (inlet air temp.) and you'll see how hot it can get in the inlet hose...hot air will see the ECU pulling the timing to protect the engine...hence producing less power.

Ideally you want to take cold air from outside, filter it efficiently with little or no restriction, and get it to the TB whilst keeping it as cold as possible...hence the insulating properties of plastic are a good thing! Plastic doesn't insulate too well when there are a load of 25mm holes in it letting damn hot air in!
The airbox is a good design, and certainly good enough for 190-200 BHP where the cams/inlet manifold start to hinder you getting any more...so why ruin a perfectly good design?

Of all the CAIs, different filters, airboxes etc I've tried and dynod, this works the best all round, road and track, all weathers etc.
It's not a huge gain...but it's repeatable and a gain none the less.

Smooth out the TB at the same time and you can get a wee bit more too.


You'll get more noise from a drilled airbox though...

[robz]

hey, i think this should be stickied!
its brill!
now i can see what i need to do properly when i get round to it!!
thanks m8!

[MK3TDi1996]

Good write up man and thanks for the info.

I wonder though, i have the 1.9 tdi AHU engine, of course being the diesel, my airbox is slightly different.

What do I need to differently with regards to modding my airbox?


thanks

[Ess_Three]

Good write up man and thanks for the info.

I wonder though, i have the 1.9 tdi AHU engine, of course being the diesel, my airbox is slightly different.

What do I need to differently with regards to modding my airbox?


thanks

Having never seen a diesel airbox...I can't say. But probably not a lot different...
The principle is the same, as much cold air in as possible and as few sharp edges and restrictions from the inside to the TB/inlet manidold as possible.

Can you post up pics of the insides of your TDI airbox?

[MK3TDi1996]

I can certainly take pictures, but how do I post them! lol