03 Z33 TT

Hey all-

I've always tried to solve my problems with the search feature, and for the most part it has treated me well.. but this time I'm stumped! Here's the story, bear with me :

Got my Greddy TT kit up and running, TiAL wastegates only had the small yellow springs (rated for 3.8 psi) so I grabbed an air regulator from my work to substitute as an MBC for the time being. The bank has been stretched thin since finishing the project, so I had to make do. Anyways, the car got tuned at 6 psi, made 370 whp. I HAD to change out that regulator though, it had a plastic body and some plastic internal components that expand and contract with heat, and when the hood is shut causes the pressure to spike or drop 1.5 to 2 psi, about a 3-5 psi range. It stayed steady while tuning because it was a nice 72 degree day and they had that huge prop fan on the front end the whole time..

Here lies my problem: I picked up an actual MBC finally, and can no longer regulate my boost pressure past what the spring is set at! No matter how far in or out I thread the adjustment ****, I stay steady at 3.5 psi or so. I've even tried swapping the MBC around thinking the instructions were wrong (I knew better).

I'm including a couple MS Paint diagrams I made to help explain what I'm doing, and please correct me if there's anything wrong that I'm doing. I believe I have everything ran per manufacturer's instructions, so I dunno. Help me out! <btw, this is exactly how I had my origional regulator piped, and it worked just fine>

Cux350z

iTrader: (162)

is there a check valve in the MBC?

Flip it around?

plumbing looks right

03 Z33 TT

Negative on the check valve, the MBC is just a simple screw and ball, I took it apart to make sure everything was seating properly.

I did try flipping the MBC, but I got zero boost pressure as there was no longer any additional force keeping the wastegate shut..

As a side note, my tuner tried one of his Perrin units and it was doing the same thing! We concluded that his MBC was just shot since it has been used for several years, but now I'm just stuck. I want to get the TXS DTEC EBC to go along with my UTEC, but if I'm already having this issue, I don't want to spend the cash on it and still have this problem.

Effin' cars, man. Talk about a rollercoaster ride O.o

15lb.test

Sorry.. noob here.. don't understand what the blue lines are?

03 Z33 TT

haha no problems, I just colored the lines a different color to make it less-difficult to read ^ ^

Anyone have any Ideas, I think I covered most of the possible scenarios but I've got to be missing something. Like I said, my *other* regulator that was actually designed to handle up to 125 psi can push the wastegates to the pressure I want, but with the MBC using the same tubing diagram can't do it. What gives!!

str8dum1

iTrader: (11)

have you tried taking all the lines off the wastegate and seeing if you can boost more than spring pressure. you'll know pretty quick, so be careful

meatbag

iTrader: (9)

put it back to the first pic and put the MBC inline to the bottom port of the wastegate

03 Z33 TT

Thanks str8, I'll give it a shot when I get home today. I've seen it overboost before, so I know it's at least capable of it, but I'll give it a shot and double-check to be sure.

Meat, I'll try your way too. I was wondering if I should tie the MBC to the lower wastegate lines instead of the top.. BTW, thanks for the thread you did on installing the TT kit on your car, I used a lot of your pics as reference since I did my install with engine-in like you did ^ ^

Thanks for the input all, I'll give it a shot this afternoon as long as it's not raining, and keep ya posted

03 Z33 TT

Looks like that did it, I put the MBC on the lower WG line and left the top vented, I'm getting much more boost now. It's rainy and miserable here right now, no chance for a good WOT run to really adjust it (tried, was all over the road). It's still overshooting my target PSI, but once it dries up I'll be able to dial it in. Thanks again