LS1TRUCKGUY

iTrader: (7)

truck currently has a 3" downpipe and full 3" exhaust with a 30" magnaflow that exits in front of the rear tire. . right now, the wastegate is open to atmosphere because boost could not be controlled very well at all with it routed back into the exhaust. it is annoyingly loud when the wastegate opens, and i want to route it back into the exhaust. would keeping the 3" downpipe and going to 4" exhaust be ideal?

smokeshow

iTrader: (16)

The lower the post-turbo back pressure is, the more boost it will make. What size is the wastegate, and how is it routed? And at what boost level does it overboost?

TrickTurbo

iTrader: (12)

What problem where you having with boost control.
Having full 3"exhaust will give more BP forcing the gate to open easier. Venting to atmosphere is freakishly loud. And should give you a slightly higher boost reading.

But as far as control the final number may change but the amount of swing change will be the same.
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I would do a min. of 3.5 for the final exhaust.

LS1TRUCKGUY

iTrader: (7)

Would boost creep 2-3 psi in 1st gear and another 2-3 in 2nd. With the waste gate open to atmosphere boost holds steady at 12psi and has a 2psi spike on the 2-3 shift and drops right back down to 12.
This is a stage 2 trick kit with a 70mm turbo and a 39mm wastegate

TrickTurbo

iTrader: (12)

Using a boost controller?

Choda

iTrader: (1)

I have the same kit and currently have full 3 inch but a 40 series flow master muffler. I also have the WG open dump. It holds what ever boost I set it to through the exhaust. I have never put the WG dump into the exhaust but I would think it would make more boost because its not as free flowing as an open WG would be.

I just bought all new 3 in pipes and a 30 in Magnaflow exhaust muffler that I will be putting on. I will leave the WG spring alone and see what it does. Im guessing the magnaflow muffler will flow more than the flowmaster so it will make more boost. Whenever I get around to getting the new exhaust on ill post up

Again I think the open dump helps control the boost more. Who cares if its loud, your in the throttle already if the gate is opening right?

kelsey_canard

iTrader: (5)

Seems like I see a lot of people sizing up the exhaust after the downpipe. Like go to 4" exhaust out the back after their 3" downpipe. Whats the logic of this?

TrickTurbo

iTrader: (12)

I would leave in the exhaust. I like it quiet.
And drop the gate spring down so you get the final boost you want.

LS1TRUCKGUY

iTrader: (7)

Manual boost controller

it gets into boost with very little throttle input. The waste gate starts to open just getting on the freeway sometimes, or if I have to jump on the throttle a little bit to pass a car. This turbo spools very quick

LS1TRUCKGUY

iTrader: (7)

my thinking is with th wastegate routed into the exhaust, im outflowing what this 3" exhaust can handle, causing more exhaust to run through the turbo then through the wastegate causing the boost creep issue.

the reason i say this is because there is no overboost issue when i was running 8-9psi boost. this issue started immediatley after turning up the boost to 12psi.