anyone tried one of the modified air box covers

petrolblue83911 · 05-01-2006, 11:31 AM

Just wondering if anyone has tried one of the modified air -box covers? I'm thinking of replacing mine -the strap attachment clips are breaking off, so I was looking at some of the stuff out there, I noticed that Per. Prod has a few different ones, basically it's just a new cover with wider openings at the sides-still uses stock filter

-Any opinions?-any drawbacks?

-I'm sure it won't add any power but since I need to get a new cover anyway, it could be a way to go?

Oh Haha · 05-01-2006, 01:32 PM

Here's my .02:
Don't waste your money. Until you get to the Carrerasa of 1984 and up, I don't think the open boxes do much good. Find a good used one. I drilled three 1.5 inch holes in my cover but it didn't make any difference. It looks neat and makes people wonder what it is. I have a buddie who bought a carbon fiber lid and swears his 1981 SC pulls harder. I think the new sound can be decieving. Others will hopefully chime in but I think the majority feels this way.

charleskieffner · 05-01-2006, 01:39 PM

i spent $175 bucks plus shipping for one. my old one was ratted out. read some threads and said why not. well i got the real racey sound and they say 8hp more at the rear wheels...........i havent figured out yet what 8hp more feels like. but all in all for the track with a k&n it is easier to put on then OEM box. and i got a real racey zoooomy steeeeker! figure it this way........for 8hp supposed more ponies ..............each one cost me $ 21.87 per horse power. if i had to do it again............buy a stock OEM box and drill it!

Brian 162 · 05-01-2006, 06:01 PM

I bought a fake carbon fibre oned. Makes alot of noise but not much else.

sammyg2 · 05-01-2006, 08:19 PM

I have a bridge and some swamp land for sale....................

Hans Batra · 05-01-2006, 09:53 PM

i'd actually love to drill holes in my stock box, just for the sound. would doing that actually make more sound? any info on exactly where to drill them? just three 1.5" holes, in a straight line, along the top of the box? anyone have any pictures? thanks.

regards,
hans

slodave · slodave's Garage

I drilled mine. Sound is improved under hard throttle. No real performace gains other than those your brain makes you think are there. Much like the wash and wax effect.

Dave

slodave · slodave's Garage

Quote:

Originally posted by Hans Batra
i'd actually love to drill holes in my stock box, just for the sound. would doing that actually make more sound? any info on exactly where to drill them? just three 1.5" holes, in a straight line, along the top of the box? anyone have any pictures? thanks.

regards,
hans

No pictures, but it looks like Swiss cheese.

Dave

JBO · 05-02-2006, 07:59 AM

...just take your cover off entirely and ride around the block and see what you think. I noticed no difference, not even in sound (but I have a loud sport exhaust!).

Gunter · Gunter's Garage

Quote:

Originally posted by Hans Batra
i'd actually love to drill holes in my stock box, just for the sound. would doing that actually make more sound? any info on exactly where to drill them? just three 1.5" holes, in a straight line, along the top of the box? anyone have any pictures? thanks.

regards,
hans

Keep in mind that these holes will get your filter wet when it rains or when you wash your car.
Do you want that?

The holes will make a little more noise; no HP is gained, even with a K&N filter.

I do have a good sales-lead to buy the Eiffel Tower; 100% profit guarantied!

JMPRO · JMPRO's Garage

petrolblue83911 already stated in his post that he wouldn't expect any HP gain and just wanted a new cover so why knock him with comments about buying bridges and Eiffel towers. Come on folks "Read what he wrote". Don't rag on him for asking a simple question.
JMPRO

Oh Haha · 05-02-2006, 12:22 PM

He asked for opinions, that's what he got. I wouldn't spend the money on a new box. I would upgrade with the money for other go-fastor stop fast goodies.

Yellowbird RS · 05-02-2006, 12:26 PM

Wath about the Ruf CTR air box??

JMPRO · JMPRO's Garage

The Ruf box is a very nice piece but it can't be used on a car with a/c. The air box cover interfers with the a/c condenser.
JMPRO

charleskieffner · 05-02-2006, 02:16 PM

how much more pony power does RUF airbox make? now we are talking! wayyyyyyyyyyyyyy cool! all in all, like i had mentioned the fabspeed is GOOD for noise(vrooommm), EXCELLENT for install in comparison to OEM, and as far as the 8HP more............well im still looking for them! this purchase landed me in the stupidity file! we really try to avoid this behavior...........honest! LOL! seriously getting OEM airbox is a PITA! unless you have little people w/little hands! so fabspeeds box is good for changing airfilters at track in this nasty dusty dirty environment we call ARID-ZONA!

bmgmd · bmgmd's Garage

According to Bruce Anderson's experience, there is no difference HP between a cone and a stock box with holes in it (if I remember this correctly).

It does sound meaner on hard throttle though (using a stock muffler that is).

Buy a used stock box and drill the holes. Or better yet, make a "Cup" style box (though yours may get really wet).

My box is further inside the passenger side so having an open filter doesn't really matter since it's protected from rain, etc.

Brian

Steve W · Steve W's Garage

On the 964s, I consistently measure a 5 rear wheel hp gain on the Dynojet with and without the airbox cover in the upper rpm zone. This would equal about 6 hp at the crank.

I haven't done the same experiment on the 3.2s but I have Dynojet data from owners who have performed the experiment. One owner's dyno sheet showed a 1 hp gain at 5500 and 2 hp at 6000 over a series of 3 runs with and 3 runs without the cover. Another owner dynoed without the airbox cover and filter and gained 7 hp at the wheels in the upper rpm zone. In a former issue of Excellence, Bruce Anderson noted a 3.5 conversion owner who dynoed an additional 5 hp by cutting open the airbox cover.

I think a cone filter type setup is fine, as long as it is properly designed with a smooth bell shaped intake trumpet into the square opening of the air flow meter. The 3.2 airbox also has a small intake trumpet, but not as well designed as the one on the 964s. I'd prefer to cut off the face of the stock airbox cover or cut some large holes in it vs buying some overpriced aftermarket one. If holes are cut, they should be large enough to avoid a hollow plastic box type noise. The tradeoff of any of the above mods are increased intake howl at full throttle, which some may not like. It is also important to note that max power is gained with cold air. If the air can be drawn from right under the decklid hole as the later cars, it would be ideal. With Motronic, if hot air is injested, the air intake temp sensor (the white plastic sensor in the meter shown below) will retard overall ignition timing for anti-knock protection.

Here are my versions of a properly bell shaped cone filter air intake trumpet, and a cut open 3.2 airbox cover for the stock airbox and filter

bmgmd · bmgmd's Garage

Steve,

Why not just remove everything but the rim of the stock air box?

Brian

Steve W · Steve W's Garage

That actually would be best, like in this pic. It would allow you to reach the cover clips in the back without problem:

Geronimo '74 · 05-03-2006, 03:17 AM

[QUOTE]Originally posted by Gunter
[B]Keep in mind that these holes will get your filter wet when it rains or when you wash your car.
Do you want that?

Drilled about 7 one inch holes, no water gets in, ever... and it rains here, like a motherf...er
Unless you do not submerge your car or spray the water directly on your filter, NO WATER WILL GET IN.
Drill them holes and enjoy the bear growls of your engine, under load they're fantastic.
my 0.02