Koots

I've seen turbo Honda Civics making power from 3" exhaust post-turbo, so if a 250-300HP 1.6L engine can make power over a 2.5" setup, than a heavy truck with 250-300HP stock could definitely use 3.5" or 4" exhaust.

The 3" downpipe should be fine though.

quez82

iTrader: (1)

So, if someone has a 3.5" DP and you would recommend a 4" exhaust off of that? Not 4" DP, and 3.5" exhaust?

black00chev

iTrader: (2)

you never want to run smaller pipe than what the outlet of the turbine is. so if its a 3" outlet run a 3"+ DP. It always helps to have the most free flowing exhaust you can after the turbo.

LS1TRUCKGUY

iTrader: (7)

without the boost controller and the vac reference hooked up to the bottom port on the wastegate, it makes a 5psi in 1st and 6-7 through 3rd gear

TrickTurbo

iTrader: (12)

Is that in the dp or atmosphere?

LS1TRUCKGUY

iTrader: (7)

atmosphere. last time i tried it, it made about the same in the dp. i am only having issues over 10psi. anything under 10psi, and its perfect. im stumped.

TrickTurbo

iTrader: (12)

Did you try 12+ psi with no controller?
Just swapping the spring out?

LS1TRUCKGUY

iTrader: (7)

no i havent. i dont have any other springs for it. just whats in it now.

Choda

iTrader: (1)

I think something weird is going on here. Someone already said it but it should be more consistent w higher boost setting.

TrickTurbo

iTrader: (12)

Ok. How old is this kit?
My kits use precision gates. And they come with 5 springs.

After seeing what happening. I think you have a controller glitch here.