| "cracking" at 10psi but you are producing 18psi, this is definitely a boost creep condition. Your boost response is also probably just continuing to rise as RPM increases - hitting this 18psi somewhere around redline. The theory of WG cracking pressure relative to actual pressure is not an absolute; results are going to vary. It used to be that setting the cracking pressure would result in a base boost pressure of a psi or two less. However, with all of the improvements by way of breather modifications this is no longer the case. It is also dependent on what type of downpipe you are using... What we have found is that vehicles using all of the breather mods available combined with the "divorced" style downpipes, where the turbine discharge flow and wastegate discharge flows are separated, there is high probability of boost creep. The easiest solution is simply to remove the divider block in the downpipe flange where it attaches to the turbine housing. This will allow the wastegate's discharge to experience far less backpressure and prevent creep. If your boost pressure is reaching this 18psi target somewhere around 4000RPM and then holding there, this is an entirely different problem. This could be caused by an improper wastegate calibration. When the term "Cracking pressure" is used, this is referring to the condition where there is just enough pressure applied to the actuator where you can just begin to spin the wastegate valve with your fingers. It does not mean that the wastegate is at full opening or partial opening of some distance from the valve seat. It literally means that there exists no valve clamping pressure but no motion of the valve from its seat. If this is how you have set them, then the other possibility is that your boost solenoid is leaking and not delivering full manifold pressure to the actuators. What you should do in this case is simply bypass the solenoid. Use a small length of hose to connect your pressure signal hose to your actuator hoses. This will eliminate the solenoid from the equation. If you still have overboost condition, check all of your boost control lines for any leaks. If still overboosting, apply pressure into your actuator lines and increase the pressure past the cracking pressure and verify that you are getting a full range of wastegate motion - the arm should move by ~45 degrees from close to open. IF they do not, they are binding - locate the source of the bind and correct the problem. This series of tests will cover all of the bases - if you still haven't found the problem, repeat the tests - making sure you followed the procedures properly. :)
Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the
tailor.
Albert Einstein
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