Glenn said:Just had a look and ETKA seems to agree with you. Run the other way, boost pressure can only push the DV open when there is a pressure differential across the top (manifold vacuum) & bottom (boost) of DV in which case it's supposed to be open and it can overcome the spring preload.
If boost is supposed to go in from the side, then (a) it tells me why so many Bosch DVs fail and (b) the DV spring only needs to be as strong as the Bosch preload (as N249 duty is based on that) - my Forge green is softer than Bosch - maybe why Yellow works better?
Perhaps we should avoid the use of the word chatter as it seems to confuse with wastegate chatter which isn't what I'm talking about - DV oscillation/harshness/overshoot,etc.
I am talking about Leons though, never really looked at a standard Ibiza (although I can't see why it would be any different).
If you've ever compared the force required to push open a OE valve and a Forge one, you'll know that the OE one takes significantly more to open it (even with the yellow or even blue spring in the Forge). So it might be safe to run even stiffer.
I agree about the chatter description though - any time someone mentions a DV noise, someone else says "oooo, turbo stalling" or "wastegate chatter, that's baaaad". I think DV Oscillation.