david benett

does anyone have experience with drilling holes in their stock 3.2 airbox for better flow? do you need to upgrade to a K&N to get any utility from this mod? how does it affect the sound of the engine on load?

db www.bentoracing.com

Steve W

I took off the snorkel and neatly cut two large trapezoidal like holes on the side, and used an K&N air filter. It makes for a little better airflow and throttle response, especially when done with other modifications. There is a little throatier sound on full throttle acceleration. I suggest that you could try it yourself by taking off the airbox cover and securely taping the air filter down to the airbox with some duct tape, and drive around the block a couple of miles to see if you like or notice the difference.

I had also extended the venturi like flare on the inside of the airbox with fiberglass reinforced bondo reinforced with a steel wire inside. It kind of looks like a U shaped doughnut around the snorkel when you look at it.

Steve

Face

David,
I drilled 6 1.5" holes into the right half of my 3.2L's airbox. I also upgraded to a K&N filter at the same time. I was contemplating the Cup Airbox Lid - but for $175, this way made more sense. I also trusted the advice of Steve Weiner, who recommended this method over wasting your money with a lid or conical attachment. 1.5" drill bit at Lowe's - $4.25! The holes deliver a throatier sound above 3500 RPM and under full throttle. I like it better...
Hope this helps.

Stephen Masraum

David, I think the primary change will be sound. I don't think in an otherwise stock 3.2L car you'll see a change in performance. I've read that it was done on the 964 cup cars and actually made a difference, but on 3.2's it's just noise (which is important too). Try the tape method and see if the sound would really be worth it first.

Steve W

One more thing I'd like to add is that my friend just modified his airbox cover on his '96 993 Tiptronic and in addition to the throatier sound on full throttle acceleration, he and his wife noticed a increase in off the line throttle response. He also said the fuel mileage gauge showed a higher mpg reading on the gauges driving the same daily course. 22 vs. 18 previously. Granted the 993 is different from the 3.2, but the airbox is pretty similar.

Steve

Steve W

The only problem that I've had with Bruce's test is that the comparison was taken without any compensation for the air/fuel ratio via remapping the DME or increasing the fuel pressure - at least that's what I am aware of. The Motronic box delivers a fixed quantity of fuel on full throttle that has been premapped and only on part throttle conditions does the O2 sensor adjust for air/fuel misalignments. If one were to increase airflow into a engine, but not increase the fuel quantity, you may see a slight increase in hp due to the airflow increase, but it would be offset by the loss in hp due to the lean conditions. Power drops off like a rock anytime the air/fuel exceeds the stoiciometric ratio of 14.7:1. That may be why Bruce only measured a nill to 1 hp difference.

Joe@Fabspeed

Why destroy a 911/964/993 airbox by cutting/hacking it apart when you can buy a Carbon Fiber style, Carbon Kevlar style, or silver Carrera CUP airbox coverlid replacement from Fabspeed Motorsport. These parts offer more airflow breathing than a few randon holes and have rain deflectors and look awesome. BEST PART is that as you gaze at 356s that are collectors items worth alot more when authentic........in the FUTURE & NOW you'll soon realize that the Carrera CUP airbox coverlid for any 1984-1989 911 and 1989-1994 964 will save you money and bring your car value @ sale/showtime when its complete and orginal or easily converted back to stock. You can buy a stock airbox coverlid---YOU HAVE to buy the entire airbox assembly which is quite expensive!

Lastly, synergistic horsepower gains are made and result when you reduce backpressure and improve exhaust scavenging INCONJUNCTION to improving intake breathing. The 3.2 carrera realizes gains differently than the 964/993/996 which the airbox improvements work EVEN if you do no other changes! Have a great day. Fabspeed motorsport offers proven performance packages for all 911s with T304SS European premufflers/catbypass pipes (super polished-showcar quality, lifetime piece, and look like a catalytic converter so anyone can pass a visual exam), freeflow final exhaust mufflers, matching DME chip tuned specifically for your 911s performance bolt-on modifications, and teh Carrera CUP airintake coverlid. Check it all out on our website. performance for the next millenium

Richard Bernau

Plenty of good posts here, but I reckon that modifying the airbox cover is one of the best little mods I have ever made. It costs nothing but time and it sounds great IMHO. I can't believe that people would spend $175 for a cup airbox when you can acheive the same thing with a drill and a hacksaw! Call me cheap but I love it when things cost zero dollars.

Like others I am highly sceptical about any performance increase - I certainly cannot feel any difference - but I love the sound. My wife and I both burst out laughing on the first full throttle, redline test such was the grin factor.

BTW in the UK at least you can buy a replacement airbox lid for not much at all, like GBP20-30.

klucker

Dave, don't waste your money with the Fabspeed "Cup Air Box" as 993 RS says. If you cut your cover you can always find someone selling one used cheap. Much less than $175. It's all about induction noise, but that sounds sporty, no power though.

david benett

the replies have pretty much confirmed what i previously thought. at no time did i think that this was going to net me any hp gains. it was really just an inquiry about the drilling locations and the amount of noise added. i am a confirmed flat 6 addict. love that chainsaw effect.

db
(i'd never think about spending money on this mod, sorry 993 rs)

l2c2911

Hi all

I'm trying to locate a stock airbox that Joe mentions for my '88 911 and have a question - ​​​​​​930-110-343-01 Air Filter Housing for 911 Carrera 3.2 1984-1989. I've seen some with snorkel but from searches that style is no longer available. Does anybody know if 1988's came with snorkel?

Thanks,
Larry

josephvman

I've completely cut out the cover on my 3.2 Targa airbox, and use the stock filter. My car has a Wong chip, M&K cat bypass and sport exhaust. I can't say it makes more power, but a bit more intake honk that I like, and I can't see any downside. I've had the car in heavy rain and the filter didn't get wet at all.

gdp_samson

forgot to quote

gdp_samson

Do you have a picture of what you did ?

l2c2911

Thanks Josephvman and as Samson noted, a picture would be great. BTW I did verify snorkel was original to 3.2 cars but Porsche replacement part no longer includes snorkel.