# Explanation for why GFB DV+ w/o main piston spring would behave like is should WITH main piston spring (and vice versa)...



## Thy_Harrowing (Dec 7, 2014)

Title gives you the gist of it, I'm interested in a dialogue about the subject in the title so obviously this is gonna require those of you interested in helping to either already be familiar with the GFB DV+ or to familiarize yourself now, which can be easily be done by watching this 3 well done minute video (https://www.youtube.com/watch?v=3EgXspDfI08). Thorough knowledge of FSI/K03 turbo operation is a must too. I have pretty sufficient knowledge in both but I'm not an expert and have not arrived at a particular conclusion on this so I could use some input. *Oh, and before anyone asks... yes I have already contacted GFB about this. *By all accounts GFB is a great company and I expect they will help me get to the bottom of this but the more input the better and plus I am particularly interested if this odd operation of the DV+ indicates something about the turbo functionality not being as it should be (perhaps some issue with the N75 or WG system for example) rather than the DV+ itself. That is because the DV+ is actually quite simple, elegantly so, and I cannot think of any reason why it would be behaving opposite of how it should be on its own; I feel like there must be a larger reason for why this is the case and hence I am a bit concerned.

In case you're wondering, here is why I am trying to figure this out... There is another matter I'm trying to sort out and I came across this discovery of the DV+ working opposite of how it should while in the middle of testing things to figure out that other issue. Testing to try to figure out the original issue is the whole reason I decided to try the DV+ installed WITHOUT the main piston spring in the first place... and that's how I've arrived here to the point of making this thread. I won't go into the details of the original issue but suffice to say that it is a not so great sounding noise during throttle use (different under different uses of throttle) and also 4PSI gone (18 instead of 22) but somehow NO performance/power loss nor any other signs of an issue with the car. If you are so inclined and curious for more on the original issue, here is my thread about that (http://forums.vwvortex.com/showthre...-WOT-only-Seemingly-NO-boost-loss-or-vac-leak!) 

I'll wrap this up with an explanation of what I've observed. I installed the DV+ about 8 months ago and for all this time had it installed in the recommended setup (which is with the piston main spring mentioned in the video installed). This is what gives the DV+ it's progressive nature and allows more boost to be held during shifts as explained in the vid, because with the spring action of the DV+ the DV is no longer either completely open or shut like it is stock. That way it doesn't just dump all boost when letting off throttle to shift. Aside from that benefit of having the spring installed, another side-effect - as openly stated on GFBs site for this product - is a little bit of a different noise added to the end of typical intake noise when letting off throttle. This is not a purpose of the product, just a side-effect to tolerate. Neither of these things occurred when I initially installed the DV+ with spring 8 months ago. I noticed zero difference at that time. Recently I decided to take out the DV+ and re-install WITHOUT the main piston spring to test how it may or may not change the "original" issue stated above. Removing the spring returns the DV+ to basically the stock DV functionality, completely open or shut; at that point it basically functions exactly the same as a stock DV, albeit a more expensive and sturdier one. It was then that I realized on a test drive after that I had better boost held between shifts (according to my gauge), throttle response was slightly better and the car did actually feel a bit quicker (but that's according to my butt dyno), and that extra noise that accompanies your intake noise that they say to expect when letting off the throttle was there too. WHAT THE HELL?!? How can the DV+ WITHOUT spring be functioning like it should WITH the spring and vice versa. It's perplexing as hell. But like I said in the first place, I'm not trying to find out for the sake of finding out... I found a good thing and I'm not knocking it because now my DV+ is worth the money I paid, BUT I want to know WHY this is the way it is because it can't be the DV+ itself... knowing how it works that just doesn't make sense. It has to be something else and I wonder if figuring out what that is might be the key to figuring out my original issue...

Alright GO!


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