Arthur.

Does anyone have experience with the Cup Performanc Airbox (www.fabspeed.com/airbox.html)?

It's a bit "open" so would water be able to be sucked in? They claim that it gives "real-world horsepower".

I've been reading the posts on the hole drilling, but this seems like a nice option if you ever want to restore the original part...

Jacks911

Arthur,
I have wondered about this and read many posts on this subject. It seems that this Open Air Box concept does work. Anderson responded to a question in his column in EXCELLENCE about intake airflow and basically said - modified engines of 3.2 liters and larger can benefit from improved air input and the 964 3.6 would also see benefit - he noted Porsche's Cup Air box which is like the Fabspeed unit.

But the question that goes unanswered is "is it worth the price"? Would I / you want to pay $200 US for 2 to 5 HP (8 HP less 40% to 80% marketing inflation)??? Could we even feel the difference on the road? No doubt you would want every bit you can get on the track, but what about filter life / water damage etc.? I'll be interested to hear what others have to say ... <img src="confused.gif" border="0">

jonfkaminsky

Real world testing, however, does not bear out any advantage to the drilled airbox theory, at least in vehicles that have no other significant modification to intake or exhaust. See the thread called "Performance Enhancement Study - II".

John Miles

Do it for the sound, not for power.
Fabulous sound improvement. Why pay all that cash for a filter holder. Drill your airbox and if you must, buy a spare cover in case you have to return to stock.
Drill it!

John

Adrian

Dear Jack,
I am going to jump in here and agree with you 100% on thie cost side. In our latest auto magazine issue (delivered yesterday) there is a news release about 2 new engine performance upgrades kit direct from Porsche themselves.
There is one for the 996 Twin Turbos costed at over 12,000Euros and I cannot remember the HP improvement for the Turbos. There is also a 25HP improvement available for the 986 Boxster and the 996 normally aspirated. This kit is a shade under 10,000Euros. As the article says, an expensive 25HP. 400 Euros per HP at the flywheel. The data I have on 964s collected around the world averages out to $US208 per HP improvement at the rear wheels. What does this mean purely based on the statistics. If you spend 200 bucks you are not going to see even 1HP on the rear wheels.
Ciao,
Adrian
911C4

Arthur.

Jon,

I read the thread that you pointed me to. Interesting and impressive. My understanding is that it won't bring much HP, but the sound may be better -I guess to our standards as my wife thinks the car is "just noisy"

What I'm a bit concerned about is not so much the money, but the fact the Cup airbox lid does not have holes in it, it doesn't even have a side wall, and in that respect a perfect entry for water, and get the filter soaked. Would that really happen, and if so would it hurt?

In another thread I read about Adrian's iced up filter while he's using the drilled airbox lid. It did not appear to be a problem as I understood as when he put back the factory cover, it did not make a difference in the problem he had.

Also, I read about K&N filter recalls due to rubber coming off. Should I stick to the normal filter, or would it be ok to use K&N or alike?

Adrian

Dear Arthur,
You may have misunderstood what I said. I will try and explain it better.
Drilled Airbox leads to airfilter getting wet (large parts are exposed) and then it freezes in the very cold weather. Heavy snow, heavy rain and very cold temps, overnight. Like we have had in the past few days.
Factory Cover does not cause airfilter to ice up because the airfileter is now not directly exposed to the engine bay. What can freeze up is the intake to the airbox itself. Once this is frozen airflow, is restricted, just like the intake area of a jet engine. I have to de-ice to get going. This problem is much easier to overcome than an iced up airfilter. These are extreme events but at this time of year it was a gamble, an experiment and now I know. Drilled airbox comes off for our winters here in Switzerland,
Ciao,
Adrian
911C4

PS: The placement of the airbox intake, see the photo posted by John is such that water ingestion is limited. Okay when the engine is covered in snow because somebody forgot to cover the spoiler is just bad luck. Yes, I do this sometimes, or the strong wind blow the covers off.

BS911

Hey, here's a question. I have a home-drilled airbox cover as well and fully agree that in all practicality, we are getting improved sound - not hp. However, I get the impression sometimes that it breathes better throughout the rpm range than the stock cover. I don't know if it is a smoother pick-up, more steady accelleration, more consistent throttle response, or what. But that too, could just be the ears fooling the Levi-dyno-butt-meter.

Oops - that wasn't a questions at all. How's this? Do things like drilled airboxes or exhaust mods that make "negligible" hp improvements still make real world improvements in the throttle response or similar types of "measurements?"
Thanks.

Bill Gregory

I drilled my airbox, similar to the picture that John showed above. In addition, I drilled a series of holes on the bottom of the cover to allow any water an escape path. As others have said, it does make a marked sound difference, and if it does make any hp difference, that's just a plus.

GeoC2cab

high,
Arthur, I have a drilled airbox, but I use a Factory air filter, I used the K+N but didnt really feel it was doing as good a job at filtering air as the factory one, I'm gona stick to a factory element, still sounds good, cheap to replace, and I know the job is getting done right,
Genuine Porsche replacement parts for me. <img src="graemlins/r.gif" border="0" alt="[king]" />

Jacks911

Arthur,

Another option, for more air intake and more Sound, without drilling holes. Snap off the "Horn" The intake Horn on the air box can be removed with a screw driver. There are 3 flexible tabs, just flex back, and once the horn is removed - you can snap it back on with no damage. I would guess that this does not open the intake as much as Jon's drilled holes, but it looks to me to be about a 20% larger opening than at the horn which is basically a silencer. I tried it and it does increase the sound of the intake on full throttle. Because Seattle is such a wet place I put mine back on, assuming Porsche knew what they where doing considering all weather use. If you like what you hear and want more, get out the drill .... <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />

Jeff Curtis

I wouldn't worry too much about water ingestion as the "barn door" opening sits quite high in the airbox and unless you're sitting in a lake/pond somewhere, it's VERY doubtful you would have that much water buildup in the airbox. Besides, the airbox lid sits far up in the engine compartment, and towards the front of the vehicle - except for a torrential downpour, I don't think much water could get in that area...if it did, it would just drain out anyway.

As for the air filter taking on water in freezing temps - obviously Adrian has experienced this...hard to imagine, guess it's feasible.

If you are worried about water buildup, which I seriously think is NOT an issue, do as Bill did and drill a couple of small holes along the bottom of the airbox lid.

As for investing in a "Cup Airbox Lid" - what a joke, unless you're going for asthetics, then I would definitely applaud the idea. $200 is a lot for one of those covers, although I admit the carbon-kevlar one would look pretty cool, that's about it.

So...with that said, goto your local hardware store and pick up...let's see, you're in Europe, so at least a 50mm holesaw for your favorite drill and "go to town" as John has pictured...it provides a perfect "Argh-argh Tim Allen" moment.

You will love the sound, and even if it doesn't really produce any HP...you will THINK you have more!!

Adrian

Dear Jeff,
Not only was my airfilter frozen solid, when I removed the whole lot to install the original cover I found at the bottom of the airbox a lot of debris.
My C4 is now running much better than with the drilled airbox in this weather. I also have to point out that something that has been completely missed in all these discussions is "Altitude". My C4 lives at 800 metres and commutes up to 1000 meteres and then down to 490 metres. There is no altitude compensation in our 964s. Turbos have it.
Environmental factors will play a significant role in any gains or losses and problems.
You will also be very surprised what gets into this area as well from all kinds of places,
Ciao,
Adrian
911C4