I respectfully disagree with the idea that using a MBC in the #2 tree is causing anyone to overboost their PT. I have my boost gauge connected thru the port on the top of the throttlebody so that I read the vac/boost at the intake manifold level. You cannot get a better (more accurate) indication of the boost that the intake sees than capturing the readings there or at the back of the intake manifold (Brake Booster line). By installing the MBC on the pressure side of the WGA solenoid, you still enable the waste gate actuation and SVA actuation to work as the factory intended. All you are doing is altering the amount of boost pressure that the WGA sees from the turbocharger. When you cap off the pressure side of the WGA and connect the MBC to the WG itself From pressure side of the turbocharger you change the whole dynamic of the actual waste gate operation. This is why you need to readjust the MBC when it is installed there. Not necessarily better or worse, just different. I have installed the HKs SSBOV between the throttlebody and the intercooler. I run the vacum signal from the throttlebody also. I can watch my boost gauge and even @ 1 psi boost when closing the throttlebody the BOV pops off. I have installed a check valve in the Surge valve line so that its operation is basically negated (BOV takes its place). I do get a about a 2 lb surge (which I have accounted for w/MBC adjustment). So there is no way that the SVA is dumping boost, and even if it was that is what it is supposed to do. Any waste gate actuation works two ways, it controlls the boost (output) by regulating the amount of push being provided by exhaust (input). It also acts as a saftey for the turbocharger on case of severe overboost. I am currently running 13.5 second stage boost and 7.5 first stage boost. I do not get any codes, the BOV works as advertised and the performance is excellent. I get no detonation, no high rpm miss or any other symptom that I have read about on this forum. I am running the AMX Turbo up intake, and a tuned dual exhaust setup from scottsdale. I have installed 10MM Magnecor racing Plug Wires, and a High output Screamin Deamon Coil. My plugs are gapped @ .040 (still using the original Champions).
I have a hard time believing that I am overboosting when the pressure I read at the throttlebody doesn't tell me so. I feel better regulating the input to the WGA solenoid because that (regulated) signal that is distributed throughout the saftey & performance circuits (ECU etc.) via sensor.
Do I think that there is a problem w/ the MBC installed between the WG and the pressure side of the Turbo ? No I don't. I am just more comfortable with regulating the input to the WGA and letting the rest of the system work as it was designed to.
It may be a disservice to say that anyone who has the MBC on the #2 tree is overboosting their PT. I have seen absloutley no indication of this on my PT and I have been running the TurboXs HPDSBC for 2 months now. I like the fact that controlling WGA input boost signal leaves the rest of the system in tact. This way ANY overboost (reported from a vacum line on the intercooler pipe about 12 inches from where my vac/boost gauge signal is derrived) is handled through the system in a normal fashion.
It is possible that better performance can be gained by connecting the MBC directly, and thats OK, Its just not for me.
Alan
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