black-sinner

Hi
I tried a search on this but didn't get the info i needed.
The setup is
370ci lq9
L92 heads unmilled
Truck manifold on driver side and fabbed a custom manifold for pas side (to clear a/c)
Patriot springs
Ls1speed tu1 cam
Wiesco -11 pistons
Callies rods
Stock crank
Arb studs allover
Br7 ngk plugs gapped to .025
Manual boost control

Boost never steady ( about to change to eboost 2 and tial wg to steady boost) it jumps up and down 15-19psi
Keeps hitting a wall at 5000-5300 rpm,
Here's what i did to fix it:
Changed plugs (new br7s)
Changed coils to truck units
Changed cam sensor
Fixed one bad inj connector

Still hitting 5k wall and power drops off,
tuner never got codes

Any ideas? Seeing that RPMmotorsports got 800+whp on about the same set up, i would be happy with a clean graph to 700-750whp

Mightymike2000ss

iTrader: (4)

what are the specs on your T76?

abbaskhan

Housing and Turbine specs????

Old Geezer

iTrader: (3)

Exh system back psi is?
Wastegate size is?
Data logs when this happens?
Insufficient air intake capacity?

Fbodyjunkie06

iTrader: (10)

I'd be willing to bet the back pressure is insane on a 6.0 with a 68mm turbine turbo. Take that back it is insane on that turbo and is more than likely why you're hitting a wall.

The reason the boost is jumping around is because you're getting a false reading from backpressure making it's way back into the intake and causing the boost reading to vary and jump around.

I see it time and time again people choke these ls motors to death with turbo's that are too small.

DrTurbo

iTrader: (3)

Backpressure is well over 2:1 maybe 3:1. More then likely the exhaust sides valves are floating due to the pressure.

CamaroZ28_LS1

iTrader: (5)

I'd say turbo is way too small like the others in here are saying. There are people maxing out 76mm turbo's on heads/cam LS1's well with an auto of course.

stock48

iTrader: (17)

I agree on the 68mm theory they seem to pk around 5k on a 6.0L. They'll actually make fair power but you gotta short shift em.

black-sinner

I get that my turbo is small for my engine but it was what i had on the car back when it was a 5.7l , even at that time the dyno graph would fall off at about the same rpm.

87silverbullet

iTrader: (11)

5.7 is not far off from 6.0. Put that turbo on a 4.8 and watch it go like an animal.

SPRAYED 01

iTrader: (22)

I have a 6.0 with a 79mm turbine and its done around 5300ish rpm. I makes perfect sense its bp. You can check it by buying a $50 boost gauge on ebay that goes to like 60psi. Tap into your merge or any where before the turbo. And take a friend for a ride. Im at 2:1.

black-sinner

My turbo is a turbonetics t76 unit with 3" exhuast exit (down pipe) and 3" intake , guess that's the bottle neck...

black-sinner

Any ideas what a good replacement would be? as u know those front mount systems are a tight squeez

DrTurbo

iTrader: (3)

As for right now the PTE76 is the only thing available with the larger turbine wheel. The Tnetics units will not be out with the newer turbine wheels right now until Sept.

SPRAYED 01

iTrader: (22)

How big is the newer turbine wheel going to be on the tnetics?

DrTurbo

iTrader: (3)

82/75....same as the Garrett GTS turbine, which is used in the GTS PTE units. Great turbine wheel.

rotary1307cc

iTrader: (5)

about time, that will be nice

DrTurbo

iTrader: (3)

Definitely make a nice difference. The LS guys keep getting better flowing heads, big CI's...etc. The turbines are just becoming to small. Turbine wheel makes or breaks LS based motors.

SPRAYED 01

iTrader: (22)

Will the physical size be the same as a tc78 and use a 3 inch dp?

DrTurbo

iTrader: (3)

No change to size