Recently made the switch from a '10 JCW to a GP2 and have noticed a marked difference in how the factory DV functions on the new car. The JCW was pretty straight-forward in that it held boost until I lifted, at which time it opened up and did it's thing. The GP, however, seems to have a mind of it's own some times. It appears to actuate mid-throttle, so partial lifts often trigger it - predictable and repeatable, but annoying because I sometimes loose boost when feathering the throttle. It also seems to take longer to build boost after shifting / lifting due to the valve sticking open a tad long, but I'm not sure on this one. The oddest thing I've noticed, however, is that the valve seems to be stuck open upon cold starts on some occasions - the engine will continually emit that sort-of low-level hiss usually associated with DV actuation off-boost or at low boost for a minute or two while the car warms up, during which time power is reduced noticeably. This happens randomly - mostly on a slightly warm or totally cold engine - and does not appear to be associated with any particular atmospheric conditions.

My experience up until last week was exclusively with the N14 motor, so I can't say whether this is just normal DV / recirculation activity on an N18 or if I have a faulty system. I've had an Alta CAI on both cars, so induction noises are quite distinct. Thoughts?

 

I believe most of the behaviour you describe is normal for a GP2 / N18. The N18 has double vanos on intake and outlet, vs N14 signle vanos on intake only. Vanos on this engine results in you seeing different boost numbers / behaviour under certain conditions, especially partial throttle and off throttle.

I think the cold start behaviour you describe is emissions related, trying to get the cats hot as early as possible

 

I have the DOS intake so I too can hear all the noise coming from the DV and I do experience what you are especially if I'm full boost and back off the throttle just a tad, whoosh...

 

Same here. DOS intake lets you hear all the activity going on w/the DV. FWIW, regarding your statement on maintaining boost, I would look into the Alta DV spring. It's a lot stronger than the stock spring. It dumps same when feathering the throttle, but holds boost longer and dumps quicker and more responsive than stock, at high RPM shifting. Not bad for an $18/30 min install.

 

Yeah, I was thinking of picking one up. Can't go wrong for $15 right?