Hi

I have a 964 from 91. I have read something about a modification of the airbox, which is just a simple procedure of putting more holes in it.

http://www.pelicanparts.com/techarti...ox_upgrade.htm

http://www.fabspeed.com/c2c4rs.html

Has anybody tried this and if yes, what is your experience?

I'm not expecting to get more horsepowers, but of course I don't want to lose any.
The main purpose is a better sound.

Waiting to hear about your opinion/experience.

Best Regards, Michael
http://911.go-create.dk/ (pictures of my car)

 

Hi Mike:

Adding 5-6, 2" holes to the airbox cover will not hurt a thing and in fact, helps a little especially when other modifications are done.

 

Hi Steve

Thanks a lot, I have made a BIG hole now.
It sounds great both inside the car and outside.
My girl friend is not as happy with the modification as I am, but then again the sound is only loud if you put the pedal to the metal, so under normal conditions it is not that big of a problem..

You can hear the differences by clicking the links below.
The recordings from inside the car, doesn't sound as good as in real life, because the mp3 player couldn't really handle all the noice.

The first part is without the modification, the last part is with the mod.
http://911.go-create.dk/Before_and_after_outside.wav
http://911.go-create.dk/Before_and_after_inside.wav

Best regards,
Michael

 

Michael,

This is THE most kick-*** post. Great recordings- you convinced me to do the mod.

 

lots of info on the 964 board on this

 

Back in my Ducati, rather than put holes in the cover I had bought an aluminum ring that held the filter in using the stock clips but eliminated the airbox cover completely. Any draw back to something like this the cars?

 

sorry, afterthought....I had considered cutting the inlet horn on the airbox and making it point up towards the tail for cooler air, barring driving in rain any thoughts on this? Am i just looking for excuses to tinker with the thing, be honest hahahaha

 

Rain is the reason you might not want to do this mod, and I believe the reason Porsche designed the horned cover the way they did. In a heavy rain, lots of water gets into the engine compartment and would get sucked into the airbox. I have no idea if it's a serious problem or not.

 

The horn on the cover is a Helmholz Resonator which is the technical term for the device that reduces intake noise.

Porsche shaped it like that to gain the required length of this device.

Putting several holes in the cover is not any problem in heavy rain as long as you are using an OEM filter element.

 

Any downside to doing this to an SC CIS cover? I know it won't gain anything but sound.

 

If you saw the cold air scoop that I had running on my NSX you wouldn't think twice about this mod. Essesntially I had a large funnel attached to a completely exposed side vent that channeled air directly into the intake. People mumbled about water ingestion however I never had any issue and I drove the car quite a bit in driving rain.

 

Thanks Mike, nice of you to post the audio too My wife doesn't know it, but once the 911 cab gets emission tested this week, the fabspeed premuffler and muffler, as well as this mod are going on