997S air box into 996

[Dharn55]

I got a great deal on a 997S, 3.8 liter air box that I am going to install in my 996. It is a pretty straight forward swap out, but there is one difference in the boxes that I noticed. On the 3.8 box there is a vacuum actuated valve on the smaller hose connection, the small branch of the hose that branches off about halfway up the main hose between the air box and the throttle body. On the older box there is no vacuum valve on the connection.

Does anyone know what the function/purpose of the valve is on the 3.8 box? Can I just leave if disconnected or should I connect it to the vacuum lines. It would seem that this valve closes when there is vacuum and opens as the vacuum drops, unless there is an actuator on the newer cars.

[Loren]

"On-demand resonance reservoir, Carrera S

The air filter of the 3.8 litre engine differs from that of the 3.6 litre engine through an active on-demand resonance reservoir integrated in the upper part of the air filter.

Undesired noises can be insulated by adjusting the volume of the reservoir according to engine speed, whereby sound in the passenger compartment is optimised. One of the goals in adjusting the passenger compartment sound has been to reduce background noise in the higher frequency range and to greater emphasise the sporty, load-related exhaust and intake noises between 300 and 600 Hz. Opening and closing the resonance reservoir produces an improvement in the intake noise of the 3.8 litre engine, particularly in combination with the specific intake system of the 3.8 litre engine.

This reservoir is activated via a vacuum-controlled flap as a function of engine speed and using temperature compensation. The flap opens in the temperature range between 0 and 30 °C at between approx. 4,600 and 4,800 rpm and closes at between approx. 6,000 and 6,250 rpm."

[Cloudsurfer]

I think that's one of the differences between the 7.8 and 7.8X DME's and their associated maps. I think you'd have a difficult (if not impossible) time controlling this in your car, as you don't have a DME output to that vacuum solenoid.

[andolyn]

Dharm

how did this mod work out for you?

Any Pictures?

[Dharn55]

The air box is still sitting on the shelf in my workroom. If I install it I am going to just leave the vacuum line/valve unconnected. The default position is open, and on the 996 there is no valve, it is always open.

[fpb111]

Check out this thread. Seems that if the flap is closed all of the time you will have a LAI (not CAI)

http://forums.pelicanparts.com/porsche-996-997-forum/599542-better-sound-airbox-simple-free.html