atomic seen a huge difference with his testing

https://www.performancetrucks.net/fo...ations-502074/

I have a stock 5.3 w a 70mm. Full 3 in exhaust into a flow master and out a tail pipe.It makes 8 psi and holds it steady. I installed a 3 in. Cutout last night right at the end of the down pipe and took it for a romp. I just started to lean on it and before I got to wot it was showing 11 psi. I got into it a little slower and it went up to 10. What didn't make all the sense to me is that I have an open dump on my WG so i thought the back pressure/flow of an exhaust wouldn't be much because I'm venting into the open air and only making baby power.

So I closed it and locked it shut lol. Trans, converter, and injectors are on the way (literally) once those are in then I'll play with the cut out. Maybe put the 5 lb spring in and when I wanna race, I'll open it and make 9-10???

Is every one w a turbo increasing boost w their cutout?

 

Yea last time at the track i saw 25psi before i let out...... i run 5-6psi with the cutout closed hahahaha

The back pressure isnt enough to help open the wastegate, need to go bigger.

Ill do something about it one day. But first gear i saw 5psi until right before it shifts into 2nd and it creeps up to 10psi, top of second its already at 15psi and in third it just keeps goin. I dont know what it was doin on the pass before that, but i when i looked up and saw the needle past 20 and i let out it was right at 25psi.

 

Aren't you running one of those tiny waste gates?

 

25!!! Hahaha when it went past 8 and 10 = FFFFFFFFFFFF

IT SOUNDS SO NASTY OPEN THOUGH

 

You've got to much backpressure, When your opening the cutout your improving the efficiency of the turbo allowing it to spool/boost higher. There's nothing wrong with the wastegate. What kinda setup you have?

 

Your saying that your running 25# boost? Is this on a turbo built motor? What kinda boost controller are you using?

Back pressure has nothing to do with the wastegate opening either.

 

I have trick stage 2. come with a percision wg

The 39mm Precision Turbo and Engine PW39 external wastegate features the following:
• High grade, high temperature stainless steel and billet aluminum components for the best in strength, style and functionality at an affordable price
• A 347 stainless investment cast valve body to provide consistent performance without fatigue or failure while also allowing for accurate boost control
• An internal Nickel Chromium Alloy valve
• 5 different 17-7 precipitation hardened springs for further adjustment of boost levels
• Standard bolt-style flange configuration for easy mounting
• A satin black anodized finish with 6061 aluminum billet cap
• Stainless steel inlet and outlet flanges as well as all clamps necessary for installation


I never would have thought that a straight 3" section from the DP to the rear end with a flow master 3in muffler was so much of a restrictor, but i seen it last night. Made a huge difference in spool time and over all boost

 

Yea no doubt its restricting it. Your best bet would be to run it with a flow-through muffler (one without baffles) or no muffler. The turbo will actually act as a muffler of sorts and keep the db down slightly. If you have to much drone w/o a muffler you can put a resonator to keep it in check, They wont create any back pressure either. If you have the money a custom 4" exhaust would be trick!

 

3" full exhaust plus a flow master will give you a good amount of bp.
Turbos really don't like chamber mufflers.

 

Its a Tial 38mm i just mounted it all wrong.



Its a stock LQ4, it over boosted and i let out at 25#. Im not running any type of BC, just opening the cutout.

Either its the backpressure helping to push open the wastegate or the turbo is just so choked down from the back pressure in the Downpipe-tailpipe. But either way Cutout open = Lots o boost.