Which Air Intake Position is best?....

[RedRobin]

....

I'm confused about which intake position is best - Some manufacturers claim the oem position under top of bonnet is best and others behind the headlight unit, and still others recommend fed from down below.

I'm referring to the aftermarket high flow tubular type of intake rather than those which use the stock airbox/engine cover.

All these manufacturers have excellent reputations and know what they are doing: APR and Dbilas use top grille oem position, ITG and EVOMS use behind the headlight, Forge Twintake hedges its bets and uses both. Then there are others which feed on 'lollipop' extensions from the foglight area and claim that the air is cooler down there (in spite of hot tarmac heat?). There are other good manufacturers which I haven't mentioned as examples.

HKS don't seem to care and simply drape theirs diagonally across the engine like a limp horse's dick. Yet HKS have a top notch reputation.

I think that the lower fed intakes aren't so popular because most owners are reluctant to modify their bodywork or foglight panels (not me!).

Over to you guys...............

[cmdrfire]

Well, I hope some manufacturers answer (because I want something a bit definite as well) but I'll take a stab at some of these with the big caveat that my understanding of fluid dynamics is elementary at best;

1) the OEM position - a small inlet just underneath the bonnet. Seems optimal, definitely getting cold air in from there, and Volkswagen use it for their cars (even on their race cars). There's some talk coming around from somewhere that seems to suggest that beyond a certain (high) speed that air no longer flows well into that inlet; I am not a CFD engineer but Volkswagen employs many I'm sure and would have ensured that this is not the case.
To me (and again, I'm not a CFD expert by any means) this does seem to me to be the most sensible area to locate an intake.

2) ITG/EVOMs location, behind the headlight - if you look in that area there is a lot of empty space. With the not-a-CFD-engineer caveat again, it seems to me that as you are driving along, an area of negative pressure will form there causing airflow into that position - hence the heatshield thing that the ITG and EVOMs intakes come with, to effectively block that portion off and optimise airflow to the intake. It makes sense, I suppose, but then why wouldn't Volkswagen have done this? It could be that this area becomes most effective at speed.

3) Underneath the nearside foglight grille - this is pretty simple, it's basically a ram scoop behind that area, exposed to lots of cold air. There is no "hot tarmac heat". However there are concerns that you could drive through a puddle and hydrolock the car (which still seems unlikely, as long as there is a little bit of filter exposed to air it's not going to be sucking in any water, and if the water is up to the grille you've got other things to worry about in any case). Need an open foglight grille really.

4) Over the top, HKS stylee - looks to use the OEM position, and by having the intake go over the top of the engine emulates the OEM style to a degree.

Which one is "best"? Well, with my limited understanding of CFD theory - OEM position 1) appears to be optimal for most applications.  Position 2) might be more suited to very high speed applications rather than optimising airflow for most conditions. Position 3) seems unnecessary and mostly for the "cool" and "racer" factors (it's telling that the OEM VW racecars do not use this position). Position 4) - see notes for OEM position 1).

Any people more directly experienced with CFD want to chime in?

[tony_danza]

The VW race cars may have to use the OEM kit for regs??

Most tuners I've spoken to that don't sell intakes rate the OEM kit very highly, it only comes to be a bit restrictive on Stage2+ applications... not surprisingly tuners that sell intakes tell you the OEM kit is rubbish.

I think your evaluations have some sound common sense.

[cmdrfire]

The VW race cars may have to use the OEM kit for regs??

Most tuners I've spoken to that don't sell intakes rate the OEM kit very highly, it only comes to be a bit restrictive on Stage2+ applications... not surprisingly tuners that sell intakes tell you the OEM kit is rubbish.

I think your evaluations have some sound common sense.

The VW Race cars don't use the OEM intake, they use something similar to the APR TSI intake thing. Made out of CFRP with a big conical/cylindrical filter. What I meant was the VW Race cars use the OEM intake location:

[tony_danza]

Ahh, was thinking of the VW cup racers, they all have the standard airbox. I do see your point now though....

[Top Cat]

I asked Mark at VWR when he worked there about intakes, and he concurred with you Mike. He told me that there is minimal benefit unless you have lots of power. Well his actuall words were unless you have the kind of power that Jonny C was putting under the bonnet of his ED 30 at the time. 

[cmdrfire]

I asked Mark at VWR when he worked there about intakes, and he concurred with you Mike. He told me that there is minimal benefit unless you have lots of power. Well his actuall words were unless you have the kind of power that Jonny C was putting under the bonnet of his ED 30 at the time. 

Who's Mike?

[Top Cat]

I asked Mark at VWR when he worked there about intakes, and he concurred with you Mike. He told me that there is minimal benefit unless you have lots of power. Well his actuall words were unless you have the kind of power that Jonny C was putting under the bonnet of his ED 30 at the time. 

Who's Mike?

Its That Tony.   

[Top Cat]

Sorry its just Tony Danza I used to call him That Tony but his actual name is Mike. 

[Janner_Sy]

this is easily solved though, buy the forge twintake and you have two of the options covered. best of both worlds

[cmdrfire]

this is easily solved though, buy the forge twintake and you have two of the options covered. best of both worlds

Eeh, there's still the issue of turbulence caused by a y-pipe. As I recall you usually need some sort of aero device within the pipe to mix the air smoothly, otherwise turbulence can restrict the flow of air. I'm sure forge must have done something to sort it out but it's still a factor one must be aware of.

[RedRobin]

Eeh, there's still the issue of turbulence caused by a y-pipe. As I recall you usually need some sort of aero device within the pipe to mix the air smoothly, otherwise turbulence can restrict the flow of air. I'm sure forge must have done something to sort it out but it's still a factor one must be aware of.

....Until Forge can publish just how and why their Y-pipe works, the jury is staying out as far as I'm concerned. Forge will doubtless be totally confident in how it works but I still want to know how and why.

[Msportman]

I've stuck with the OE airbox and a performance filter on my Stage 2 ED30 but I'm sure VW were happy when they researched and developed the current set especially as they use a similar system on their race cars.

[Janner_Sy]

I've stuck with the OE airbox and a performance filter on my Stage 2 ED30 but I'm sure VW were happy when they researched and developed the current set especially as they use a similar system on their race cars.

you cant ignore the fact that they have got rid of the integrated engine cover/airbox with the new TSI for an induction pipe running from the ram scoop to the turbo. surely that shows the std airbox was restictive, but the scoop in the grill is ok

[Keith@APR]

I've stuck with the OE airbox and a performance filter on my Stage 2 ED30 but I'm sure VW were happy when they researched and developed the current set especially as they use a similar system on their race cars.

you cant ignore the fact that they have got rid of the integrated engine cover/airbox with the new TSI for an induction pipe running from the ram scoop to the turbo. surely that shows the std airbox was restictive, but the scoop in the grill is ok

You will not find a higher pressure zone of incoming air outside of the engine bay other than the leading edge of the hood right where it meets the grille.  This means the OEM scoop location is by far the best spot.  If anyone can produce wind tunnel data that relays differently I am all ears but VAG's own wind tunnel testing proves this quite handily.