USDM twin swap wont boost

[ihateu3]

I recently acquired some USDM twins that have very minimal shaft play. My old JDM twins where blowing oil, but boosted fine. Upon swapping over to the USDM twins, I have been unable to make any boost, unlike all the threads I searched that are achieving only 5 PSI, I am getting nothing... As far as I can see, all vacuum hoses are hooked up, and no boost leaks that I can tell (IC piping wasn't even touched since the JDM twins). Any suggestions?

[ihateu3]

I did notice that the USDM twins had different vacuum hardlines, so I just used the JDM hardlines and hooked all vacuums up as they where on the JDM's. Looking at the USDM vacuum diagram, it still seems the JDM vac lines route to the same places.

[ma67 lover]

Did you check the actuator to see if it was loose and just dumping all the boost out the waste gate maybe?

[spud3861]

IC piping loose clamp?

[2JZ260z]

^ its almost always that. Check all your IC piping @ the Intercooler, and at Intake/Turbo inlet.
BTW, you got any spare USDM cams? <3

[EwGoetsch]

double check for boost leaks, my 1jz kept blowing off the vac lines behind the intake. My turbos are going out too but still build about 8-9 psi

[ihateu3]

I will deff check all these things, but It will be a recheck, recheck! As for the open wastegate, from my research I am seeing that I would at least get to 5PSI...., I am getting nothing... I have not touched the intercooling piping since the swap (before it boosted fine), but I am imagining that even with a boost leak I would hit some kind of PSI, not 0-0.5. The complicated twin setup makes me believe that it is a vacuum problem, but my vacuums seems to be ok, unless I somehow swapped the 4 vacuums that run behind the engine that I cannot see where they go to.

[williamb82]

sounds like a split i/c coupler somewhere. but also, i thought the usdm turbos had different vsv's and wouldnt work properly when controlled b a jdm ecu? thought they had to be rigged for ttc? i havent really looked into it much though. wont even be using my jdm twins.

[ihateu3]

Interesting, I have never heard that the VSV's where diff... However I am using the JDM VSV's with the USDM twins since they did not come with these twins... Urgh, this is annoying, it really does seem to be a vacuum problem or IC.

[ABQMK2]

I had a problem similar to is way back when a ran twins..two actually, I blew the rear turbo(not your problem here) I also blew the intake mani gasket..how's yours.? I'm sure it was fine before the twin swap, but I thought I'd throw it out there. Good luck finding the problem..my $ is on a leak somewhere.