Have you serviced your DV's ? I recently took mine apart, cleaned and regreased (Mobil 1 red syn grease, or white lithium) . I've always tested mine by pushing in the diaphragm from the bottom while applying suction to the nipple. The diaphragm should stay in the upright position without any assistance until the suction is released, when the suction is released it should release all the way back down without sticking. Repeat a few times.

I would assume you would see about .8 all the way to redline if you were running off the wastegate spring (assumming 1 bar actuators), and no leaks.

Wish I could offer more, I went through this with Todd @ Protomotive recently. I also ran a pressure test at about 20 psi, and checked for leaks.

Good luck.

Do a pressure test from the turbos like I suggested via email... all your problems will show up.... forget doing the dvs test this and that.. the leak test as I suggested does all of that and much more.... trust me...

also, inspect the turbos... the compressor.. make sure they are not hitting the housing as they spin...

Thanks for the input Markski and the problem would most likely be mechanical in which would be found as you suggested.

Give me a call tomorrow and I will let my desk know.


Best Regards,
Scott

No problem,
thanks
mark

I agree. Check you hose connections carefully. I bet one is not securely fastened, especially since you are hearing a loud whoosh at higher boost.

Thanks everyone for your inputs! Inspector, MBailey, Earl, Markski (as always), Scott, TTDude, Neil @ Switzer, Jake @ Tial, and Mark @ Agency Power

MY mechanics will hopefully have this solved tomorrow.

Good luck!

If the intake is collapsing above the engine, wouldn't that cause the diverter valves to open up?

Do you mean the intake pipes are collapsing presumably from vacuum? This would kill the boost but I dont think it would cause the valves to open up and give a whooshing sound you describe.

Why are you asking this?

if you have a leak before the turbo that would not cause your problem.. that is the non pressure side...

shouldn't, but what intake piping do you have!? If you're at 0.6bar with the throttle open, the DVs should be shut.

The guys pressure tested everything..found a few small leaks and tightened everything up. Nothing changed.

The car is boosting up to .8 or .9 then immediately drops to 0.53 bar stable.

Mechanics think it is the intake piping above the engine.

Next step is to dyno the car with the turbos open to the air (i will make sure they brush and blow any crap out of the dyno way). If the car makes 1 bar of boost and holds it there we know the intake is in fact the problem.

Sound right?

where did you pressure test from? did you take out the stock N75 grey valve?
what is the greddy reading when car is at idle...
dyno will not solve or find the issue

Boost is actually a resistance. Are you going to take the hoses off the ouput of the compressor or the input? Either way is bad. Input will allow you to suck stuff in, and won't tell you much, with the output open, that will likely over spin the turbo to reach your target boost...which how are you going to measure if this is open?

Ok, so all leaks are fixed and still not boosting. How old are the spark plugs? I had old plugs once and it would not boost past 0.5 bar.