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Message: [QUOTE="Hotrodtractor, post: 91628, member: 25"] Variables in waste gate setup: Spring rate Spring preload Valve face diameter Pressure above the diaphragm Pressure below the diaphragm. How those variable effect waste gate tuning: Spring rate is mostly used to set up initial spring preload to keep the waste gate shut - but can have some effect on how far the gate opens at any given waste gate condition (the higher the rate - the harder the gate is to move the farther open it becomes). Spring preload - some waste gates have adjustable spring preload that allows further tweaking of the initial seat pressure of the waste gate. Valve face diameter - Exhaust pressure is pushing against the valve face - the larger the face - the more surface area that pressure can push against trying to open the gate. The diaphragm has ports above and below the diaphragm - and there are LOTS of ways to set these up depending on what results you might be looking for. BUT no matter how you set them up - having more pressure on one side versus the other will want to make the unit want to either try and open or try and close. I've seen both ports open to atmosphere, regulated boost to either one with the other one open to atmosphere, unregulated boost to either one with the other one open to atmosphere, regulated boost to one with unregulated boost to the opposite, etc..... I prefer a heavy spring - with a good sized gate - with unregulated boost below the diaphragm - and regulated boost tot he top of the diaphragm as a good starting point for most setups - but depending on the application and desired outcome all of those items could change for any given setup. For instance - my Dmax usually has a heavy spring with regulated boost to the top of the diaphragm and the lower open to atmosphere - this allows the wastegate to slightly open when I suddenly go WOT - then the boost begins to hold it closed until the backpressure is strong enough to overcome the combination of the spring's seat pressure with the added force of the boost on top and it starts bleeding exhaust gases around the charger. There are DOZENS of ways of setting up a wastegate - and they are all good for certain things and several different ways can be used to achieve the same basic thing. Confused yet? :D [/QUOTE]