Bambi'10silverado

hey guys I'm new to the form, and I have a problem with my silverado. it's a 2010 4.8 and I just installed a race mmi twin turbo kit on it. the problem is that I can't get it to build more that 3.5 lbs of boost. it has no leaks within the system. the bov isn't leaking. they are internally wastegasted and the wastegates are set at 12psi right now. bother of the turbos are good, I had them both checked out by two different turbo shops in my area. it isn't an blockage in the exhaust because I disconnected the exhaust and that didn't help. it has stock injectors and fuel pump which I heard was good until about 8 psi. bother turbos are 50mm inducer, 76mm exducer

JoeNova

Those look like the DNA motoring twin 50s.
I just tuned a 4.8 last night with these exact turbos. Made 20 PSI at 4500 RPM. Truck belongs to a friend of mine.

What are you doing for a tune, MAP sensor, boost controller? How are your vacuum lines setup for the wastegates?

Bambi'10silverado

tuning off the map sensor. no boost controller. the turbos are internally wastegated and the vacum lines came off the intake manifold to the wastegate but I took that off and ran the lines from the brass fitting on the turbo to the wastegate

JoeNova

It will build less boost when referenced from the compressors. Put the wastegate line back on the intake.

Stock MAP sensor? Whats being used to tune with, HPTuners? Do you have a wideband?

kingtal0n

iTrader: (1)

you need to pressure test the system

93camaro_zzz

iTrader: (13)

^ This. Specifically the pipes between the turbos, and the Throttle body. Also look for vacuum leaks around the manifold.

gametech

iTrader: (1)

Once you find the cold side leak, find the hot side leak. After that you will have enough boost to need tuning. At that point you will realize how stunningly inadequate your fuel system is. Whoever told you the stock fuel injectors were good to 8psi either lives on MT Everest, or lied to you. The stock fuel pump with 60# injectors will only hold up to short runs at 450rwhp. I found that out the hard way at Road Atlanta.

Bambi'10silverado

I pressure tested from each turbo to the intake hose at the throttle body. being tuned with a zl1 map sensor I think I can't rember exactly which model it's from but it's the one that handles boost better

LSrBest

iTrader: (1)

How did this set up work out?