SuperZ

iTrader: (2)

ok so when we converted from the T4 GT-42 76mm the bolting part was cut around and the T6 flange blended in leaving the merge size flowing up into the turbo the same.
Basically the perimeter flange is T6 but the flow hole is T4 still.

Is this my Low Boost problem> the t4 hole not flowing enough to spool the S91 enough to build more than 12psi?

topend

how is your exhaust back pressure pre turbo and after turbo????. is your wastegate working properly??? Any leaks in the intercooler/cold side plumbing??? vacuum leaks??

Alot of possibilities......start testing

SuperZ

iTrader: (2)

i have been testing this is my 4th post about this.No leaks blocked off WG and no change so that makes me think the problem is before the turbo?
Maybe the T4 sized hole duznt have enough volume to boost the S91 higher

SuperZ

iTrader: (2)

ttt for the sunday crew
ill get a pic up today

52172

iTrader: (2)

I would think the T4 hole is the problem. That is a large turbo that needs a larger hole.

TurboZ28408

iTrader: (18)

i think its more you have a leak somewhere

52172

iTrader: (2)

Have you checked for leaks?

Shawn @ VA Speed

iTrader: (3)

how about a run down on the entire system,header size,crossover size,intercooler,cold side piping sizes,etc.

Cmarsh

I don't think that much of a differance in size is going to cause huge problems, especially with spool. MAYBE topend power, but not much

Stupid Boost

iTrader: (1)

You've got another problem,I ran a t4,91 y2k and never had a problem makin 25 pounds,so hunt a leak or something else.

52172

iTrader: (2)

You might be right, but his turbo is a T-6 exhaust housing that is about twice the size of your t-4.

SuperZ

iTrader: (2)

Yeah I have a t6 turbo not a t4.
its a t4size hole feeding the S91 t6

its the standard 2.5s from the 6.0 manifolds to the flange.3 inter cooler and pipe.

if that is the prob I dont know if I should mess with new hot parts for the biggler true t6 flange or if i should just put a pte-88 t4 on there

Shawn @ VA Speed

iTrader: (3)

I would be curious to see the intake pressure at the turbo.also what a/r is the turbine housing?

SuperZ

iTrader: (2)

its the 1.1

Shawn @ VA Speed

iTrader: (3)

downpipe size?

SuperZ

iTrader: (2)

5inch transitions to 4 then to 4 oval pipe under the car with 4 oval spintech muffler

Shawn @ VA Speed

iTrader: (3)

hmmmm,i dont think it's a hot side problem,was the turbo the only thing you changed,or did you make other chages as well?what was the boost with the old turbo?

SuperZ

iTrader: (2)

I may need to check my inter cooler.
The reason i thought it would be before the turbo is because the Wg isnt opening at all and I thought if the leak was after the turbo then the WG would still be opening then leaking it off post turbo

SuperZ

iTrader: (2)

ttt
anyone have anything about the flange situation before i go through all the crap to change it?

black98ws6ta

iTrader: (77)

I am thinking the scroll of the turbine would be more of a restriction then the t4 flange. I have not read the full thread, have you measured backpressure?


If you have a 16 psi spring(example) and you are only making 12 psi then the wastegate will not be opening. It doesnt matter if it is an exhaust or intake leak causing your problems.....if you do not have enough boost the gate will not be opening.

I would pull the valve covers and loosen the rockers, add pressure and check for leaks on the hot and cold sides.