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944 S2 airbox mod

C

charles.y

New member
There are previous threads discussed in various forums about cutting holes (4 in the 968 and 20 in the 944 S2) in the airbox which claims to increase approx 10 bhp. I wonder if anyone has tried this in the S2 and what is the verdict, pros & cons?

BTW, I have replaced the stock air filter with the K&N one.

Charles
 
Charles,

I have done this. 4 very large holes in the front of the airbox on an S2.

Conclusions? It makes the car feel more responsive wiht small throttle openings. You don't need to push the pedal as much to make the car go. It's slightly throatier on wide-open throttle acceleration, and that's about it.

It does make the car 'feel' different, although I can't quite put my finger on why. I think it's to do with the greater responsiveness at small throttle openings, as above.

I reasoned that it would liberate some more horses, but am not sure. It doesn't actually feel any much faster as a result. I would question the figure of 10bhp.

One point to note - on the S2, the air box is under the badge panel, and cutting holes in the front of it does open the front to the airstream approaching the car. This should offer a small degree of ram-charging at high speed, which *may* be happening (wouldn't like to swear to it but it does cruise very well at high speed.) It does also (in theory) mean that small stones being flicked at high speed at the front of the car could pierce the air filter and enter the inlet tract. However, looking at it carefully, I think that although this is possible, it is extremely unlikely (and a risk I am happy to take.)

FWIW, I have a standard air filter.

If you are in the London area and fancy swapping airboxes to see what the difference is like, I'm quite happy to play ...


Oli.
 
Not the same thing I realise, but my 964 came with 2 big holes in the air box. It made a horrible noise (I do like induction noise, but this was a resonance) so I taped them over with Duck tape and it made things much quieter with no noticeable degradation in performance. I always find it's much easuer to spot things getting worse than better so I'm pretty happy it made no difference to go. Of course the airbox in question is in the boot in my application so gets no ram air effect.
 
Interesting comments. To maximize the ram air effect (I don't even know what that means), how about taking the airbox front cover off and cover it with a think metal mesh (so that water and smaller debris don't get sucked into)?

Charles
 
I was going to put a cone type induction lit on my turbo but decided i wanted to keep it looking standard so have ordered a k&n panel filter,is it worth putting holes in the airbox and if so where do they need to be. Fen i once bought a mk2 golf gti that had the entire bottom of the air box cut out and i agree with you induction noise is good but this was just too much !!!
 
What you'd lose with the Turbo is that currently it draws air from the nearside front wheelarch, which is if not cool at least not in the engine bay. If you make holes in the airbox you will be taking air from the area behind the intercooler/radiator/condenser and immediately above the front of the engine block. I suspect that is quite a warm area - with the S2 the airbox is in front of the radiator hence it gets cool air from there.

In terms of ram air effect I don't know it makes much difference unless you funnel the air into a sealed box that can therefore become slightly pressurised (and it would be very slightly). Drawing cool air with little resistance is probably the realistic best you can do. On the other hand I don't think it makes much difference to a K&N type filter element if it gets a little bit of water on it now and again, and any big objects like bits of gravel or insects will not get past a filter. It might be a good idea to ensure the airbox stays dry if you run a paper filter. To really maximise the benefit on an S2 it would be worth having a hole in the badge panel You could possibly route a sealed intake into it somehow so you could harvest some positive pressure at speed. It starts to get interesting then, but I'm a sucker for holes in the front of cars (provided they do something).
 
Fen ,What do you think is the best option for my turbo ,just put the k&n panel filter in and leave it at that ???
 
IMHO the absolute best option is the standard paper filter changed regularly. Unless you have a vastly modified car a free flowing filter will make very little difference and you run the risk of having inadequate filtration if you do not stick to the cleaning regime religiously.

Ideally you would want a filter at the end of a straight pipe behind the offside headlamp, but in its own sealed enclosure so that it draws no warm air from the engine bay. This removes the convoluted, folded back route of the standard airbox and ensures cool air is used from the hole in to the wheel arch.

Having said all this my own Turbo has currently, temporarily got a cone filter sitting in place of the standard airbox behind the radiator and intercooler (absolute worst place). This is purely for fitment reasons whilst I still use the AFM in a slightly altered position due to the 4" inlet to the turbocharger. Once I go MAF, it will be either in its on enclosure behind the headlight or even hidden inside the wheel arch liner
 
That's all I ever did when I had an airbox, but then I haven't had an airbox for over 5 years (and that includes 2 periods of running the car before any smart arse suggests it has been in the garage the whole time).

Your options are to stick to the standard filter, go with a K&N panel, go with one of the cone filter kits that place the filter where the airbox was or go with a kit that puts the filter behind the headlight.

Personally I think the first or last is the one to go with. I never noticed any benefit from a K&N element in my Turbo, nor in my S2 cab. A filter behind the nearside headlight is the best choice in my opinion, but it doesn't look standard.
 
I think i will stick with the k&n panel filter for now but may look in to putting a ramcharger behind the headlights as i should have a bit of room once the pop up lights and washer bottle are removed !!!
 
ORIGINAL: Diver944
Once I go MAF, it will be either in its on enclosure behind the headlight or even hidden inside the wheel arch liner
Click to expand...

Surely you mean MAP with a nice standalone system.? That car deserves a decent EMS after all the effort that has gone into it.
 
I know what you mean, but to be honest I might even stick with the AFM and a custom remap. If that lands me close to 400bhp with torque in the mid 400's I'll be more than happy and then I'll just drive the thing [:D]

I'd worry that with a MAP and a good standalone then my 3.2 might be getting well over 500bhp which is just silly on a road/track car (plus the torque might just throw the gearbox out the back [:eek:]). There would be precious few occasions where I could even put my foot flat to the floor and where's the fun in that [&:]
 
ORIGINAL: Diver944
IMHO the absolute best option is the standard paper filter changed regularly. Unless you have a vastly modified car a free flowing filter will make very little difference and you run the risk of having inadequate filtration if you do not stick to the cleaning regime religiously.
Click to expand...

I'd go along with that.
 
Paul, You don't have to map the car for 500bhp! You could simply map the car for other characteristics such as a lower and flatter power and torque curve. Going for max power means you get a spikey powerband which is not as nice to drive as a flatter power curve that has a lower max power that is available over more of the rev range - it's the area under the curve that really matters. With a MAF/MAP and custom mapping you have more control to achive this.

I've read on several forums and other sites that K&N filters will only give you increased performance over a std paper filter for the first 1k miles or so. After that they become clogged to such an extent that they will provide just as much resistance than a standard paper filter, so unless you are going to clean your K&N filter every 1k miles or more frequently than that you are unlikely to sustain any power increase you might notice.

I've seen a screen on the Lindsay Racing website with a big rubber seal around the top edge that completely cuts off the behind the headlight cone filters from the rest of the engine bay (very much like the shield that wraps itself around the brake fluid resevoir) and therefore guarantees you are not going to be sucking in any warm air from the engine bay. This seems to be the best solution in my mind. The potential problems I see with hiding the filter inside the wheel arch is that it makes it a real pain in the backside to clean the filter regularly and I doubt the wheel arch liners keep out all water and road crud thrown up by the tyres therefore you run the risk of getting mucky road water splashing onto the filter.
 
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