Acoustic Valve does what?

[Jonc]

Not a lot is the answer!!

I've finally removed the valve following the guide posted on this site. I also replaced the hoses with flexible alloy items, 50mm dia. for the lower intake (1st pic) and 60mm dia. for the side intake (2nd pic) using the orignial plastic fittings.

Performance wise I didn't feel it made much of a difference. It has however, improved low rev pickup, in that it seems happier than before pottering around the 1k-2k rpm mark. Pick up at these revs is much improved.

Out of curiousity, I decided to reconnect the valve back up, ie just the vaccum pipe and the electrical plug, and here is the result of what it does.

http://www.youtube.com/watch?v=w4XWOpLIm3E

I also did a few runs 0-100, unscientific I know, but despite not actually "feeling" any difference, the timings on the video says otherwise.

Before: (cold-ish evening)
http://www.youtube.com/watch?v=QrC01R3Rw9c

After: (sunny afternoon)
http://www.youtube.com/watch?v=X008U7Ea71s

Admittedly it is difficult to tell as video quality is poor on on youtube, but the orignal footage played back on my pc shows that it is around a second quicker through the gears to the ton. Not much you might say, but not bad for a £20 mod! Not sure why the valve did nothing, as my engine was warm at the time, my only theory is that the valve only works when the engine is cold to aid emissions. Is this proof that the AV does nothing for performance, you decide!!

 

[Cue]

totally agree, it's there to restrict airflow into the engine.

 

[George K]

In theory teh a/v should not restrict feed into the airbox, as there are two separate 62 mm feeds into the bottom half airbox if you look carefully. The object of the a/v is to reduce external induction noise in the 'drive by' test applied in some countries - notably Switzerland. No body has ever found out under what conditions it is operative, i.e closed, could be done quite simply by wiring an indicator light inotothe control circuit.

I have removed mine and replaced it by a 75 mm pipe in exactly the same place as the original - it took a lot of work to make up a new inlet which was properly blended into the bottom half of the airbox - shaped aluminium pipe and lots of dremelling. Difficult to tell if there are any benefits other than noise (which is an irritation as far as I am concerned), but I wanted to optimise the inlet system before carrying out other mods. I still have not seen any independent evidence ot prove that the more exotic IK's produie any measurable benefits, so decided that this was the most cost effective approach.

 

[Jonc]

Those were my thoughts precisely. An sealed induction kit is not worth the cost for the gains if any. Incidentally, I had an open induction kit when I bought the car, and is slower than with the standard airbox, even before modification. I did get a lot of induction roar, but thats not what I'm into.

 

[polarbert]

Thanks for this, I was contemplating whether to take mine off but I won't bother now. Don't usually rag the engine when its cold anyway so its not a problem!

 

[T7PHY]

Yup, couldn't agree more. Fiddling about with these things causes power losses if anything... I noticed the ITG Panel Filter I fitted was actually detrimental, so went back to the standard filter. Renault don't muck about developing a car for nothing.

 

[Cue]

My tests have me quicker post airbox modification the pre mod (albeit a bit unscientific).