well i have a twin turbo setup lt1 fuel injected in my 89' 1500 pickup the issue i am having is that the turbo is taking to long to spool.

heres what i have as my setup

stock bottom ended 350lt1
twin turbo t3/t4 .50 fronts/.63 rears
internally gated with dual port wastegate acutators set for 6psi
front mount intercooler
complete fuel system upgraded with boost refrenced AFPR and supra intank with kenne bell boost a pump.
pcm tuned by pcmforless and working well.


there are no leaks on the cold side of the piping to engine and thru FMIC all clamps are t-bolt clamps with silicone new connectors. fuel pressure rises when throttle is applied and never drops.
i have the internal wastegates working normally with no type of boost controller whatsoever top vacuum line to compressor side of housing and bottom port open to atmosphere. my question here is when i adjust the Internalgate to its lowest setting 6psi the rod which is threaded i have to make the flapper close on the inside of the turbo nice and tight there cant be any play there correct?

what ends up happening in driving conditions is i am familiar with these small turbos on a v8 spool up very quickly and maintain boost as engine goes thru gears and powerband, but i am not getting that with this setup. When i leave from a stop vacuum closes quick to 0 at part throttle but then when i go right into WOT it takes past 3500 rpms or more to get the boost to 6psi and it holds it without a problem but no where as fast as my previous builds with these turbos, what gives? my only difference on other builds was external gates instead of internal actuators could this be my problem? that the gates arent opening or are letting out the boost and not letting the turbos build it?


im at whits end i have been building this project for almost 2 years now and i finally got to pull it out of the yard this evening and it runs but not as hard as it should be in my taste, to me it seems as if its SPOOLING WAY TO SLOW.


can anyone shine some insight on why my setup is spooling up so slow, its getting to the set psi of the internal gates but taking way to long.

 

That's like having a single 1.26 A/R housing. too big for a fairly stock LT1. I would use .48's

 

The wastegate reference hooked up to the correct port (should it be on the bottom port instead of the top)?

 

nope it should be on the top port. the internal wastegates work opposite of a external wastegate.

the external gate pulls the valve up to release and regulate boost, the internal gate pushs the the rod out to regulate the boost.

i just adjusted the wastegates they were to loose and needed to have more tension or pressure to hold the flappers shut now the car comes on boost like a raped ape.im happy with the 5psi

 

seems like those turbos are a lil too large for your set-up, you would have been better off with a single turbo set-up, ik it dosent help, but from the sound of your post it dosent seem like its leaking boost or anything is stuck

 

Those turbos are NO WHERES NEAR too big for a normal 350. They are actually on the small side; if he was looking for much more than 8-10 psi he'd probably have to up-size.

 

I'm assuming he's means 50 trim t3/t4's? which each will support 450hp.
Definitely not on the small side for a fairly stock (?) LT1 on 6psi of boost.
Even at a low pressure ratio they'll efficiently support 600hp.