The Project Pad

It makes sense to me, pressure differential allows the valve to open via greater pressure in the lower chamber than the spring.

It really should work either way... in the bottom-port-only case, you limit boost by adding pressure to the bottom chamber. In the top+bottom port case with valve in the top port, you limit boost by limiting pressure to the top port. The two methods just call for opposing boost controller operation/configuration (one has the valve limiting pressure/duty cycle to lower/raise boost, the other has it increasing pressure/duty cycle to limit/lower boost).

Just so I have this straight, if I am going to one a 'heavy duty' N75, then I need to hook it up the way Darin has it, or will 'in line' work ok?

There are several ways to skin a cat. You can control boost with lower chamber only, but that doesn't counter act the force pushing on the wastegate valve surface, so eventually exhaust back pressure will open. Putting pressure on the top chamber counter acts the exhaust pressure. So, if you want high boost, the upper chamber really needs to see a boost reference. The style of waste gate solenoid also has a bearing on operation. Most valves will be normally closed and provide boost reference to the lower chamber even if no signal is given, this is for default spring control. Others are normally open and would go full boost with out a signal on the lower chamber, but wastegate spring control when not getting a signal when hooked up to the upper chamber.

i use a stock audi gate, a 2.2 bar spring and bleed off the pressure from the bottom port. No line to the top port.

By the way Darin, glad to see that it is working. You outta drive it up here to drop off the loaner tools or drop them in the mail for me. Glad the car is driving well and better off, shifting like butter..

Brent - the inspection is due in September. I need to drive up next week to do that, thread the shift rod for the S4 shift knob, return your tools, repair a torn CV boot, look into having only one key to turn the car on AND lock the doors and figure out wiring for the 2 plug transmission connector (I believe that is for the reverse lights).

Let me know what day is best.

Thanks,

8 pounds at birth! Congrats!

clever nick!! well done!

The two pin plug is reverse lights, cv boot is doable, threading shifter, also no problem, and the IM should be ok. The laws have changed since last year, much more strict and the emission department has a webcam that they use during the test but I am sure we can get thru.

savagerocco wrote: The laws have changed since last year, much more strict and the emission department has a webcam that they use during the test but I am sure we can get thru.

feck....big brother much. that sucks.

ShavedQuattro wrote:clever nick!! well done!

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