NICKOWS, Hi. A CAI or SRI does not provide the same sound deadening qualities as a stock air-filter, which, along with the resonator, is deliberately designed to hush up induction.
If you listen to a stock engine, and know what you are listening for, you can hear the BOV working, as it must with all turbo engines if you are to avoid the one issue it is put in place to deal with and that is compressor stall on throttle closure.
With either of the new fitments, you will not only get the induction hiss that you never heard with a stock filter, but also the sound of the BOV letting go to bypass as intended. And if you listen carefully, you can sometimes also hear your turbo responding to the increased bypass pressure.
You will not be getting so much more air with a CAI or SRI that your BOV/turbo setup is going to have any problem handling it on throttle closure, with respect to the stock setup.
Once you have driven with a more open system, your ears will become attuned to all the little sounds related to the induction system, such that if you revert to stock, you will still be far more aware of them than you are now.
BTW, the A/F ratio is dealt with by the MAF which is measuring the air temp and volume after the SRI/or CAI. It would only be an issue if you had a BOV which vents to atmosphere (VTA) and this means that your ECU would be metering fuel for air the engine never gets - and hence produces a rich mixture and consequent backfires*. Not a problem in your case with your 100% bypass BOV, as the air volume in the system remains the same throttle on to throttle off.
More BTW, the stock BOV is often said to be set to "leak" at around 15psi as a protective measure. This might be more apocryphal than reality, because under boost the top and bottom sides of the piston are at equal pressure when the throttle body valve is open, so there is no pressure exerted on the piston to open it under normal boost range. Other BOV's without the top line (off the intake manifold - post throttle plate) may open under excess pressure. There is a lot of S$#^ talked about BOV's leaking and this gives rise to a lot more C*&% about how screwing down a BOV with an adjustable piston will increase boost. It's tripe. All that will do is make it harder for the BOV to dump air and eliminate the compressor stall you might be experiencing. But if you have it set too light you might VTA too much and induce the enrichment I referred to above*, and incidentally wash your cylinder walls with raw fuel and mess up your cat.
Cheers
Last edited by Doug_MPS6; 09-12-2009 at 01:23 PM.
CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18