Hmmmm

So what's everyone's ideas about me running two WGs? Set one to a street friendly 6psi and a second one w a 10psi spring as a fail safe for when I open the cut out and wanna make noise. Run both gates off the same vacuum hose because it's going to show 6 and open the first one, the cut out will produce more boost and open the 2nd gate HOPEFULLY keeping the total boost to the second WG setting

 

No no no no no lol! This is getting to complicated. First... (1)Have you had this setup professionally tuned? (2) If yes what boost level was it tuned at? (3) do you know at what level you start getting detonation? (4) is this a 5.3, 5.7, 6.0? Stock motor or built? (4) Is there any particular reason your stuck on running spring actuated waste gates!

 

It is not always possible to place a single large wastegate where it will be both effective, and aesthetically pleasing. Placement has just as much to do with how effective a wastegate is as its size. Sometimes it is a lot easier to use 2 small ones rather than one big one.

You not only need to match the gate to the turbo but also to the engine. I cant comment on his kit, but I will say most turbo setups are forgiving in terms of boost management. What do I mean by that? Well, how long are most people full throttle? Probably 10-15 seconds max depending on mods. Well as im sure you know turbos and engines are very dynamic, ie constantly changing. In that 15 seconds you have at least 2 gear shifts and sweep across the airflow range multiple times. Basically the entire time at WOT is a transient response. What is the turbo doing all of this? Speeding up and slowing down obviously. It is the wastegates job to "waste" enough exhaust to keep the turbo speed down, and it does this by opening a valve before the turbine and by-passing the turbine wheel.

So ideally the wastegate can get rid of enough gas, in all conditions, to keep the boost under control. But what happens when you are in it for a really long time? The transient response of the system (engine+turbo) has pretty much decayed and it is approaching a steady state condition. If your wastegate system is fine this wont be a problem, but what if the gate is ineffective for whatever reason? Lets say you start from a stop and give it full throttle. The turbo takes a second to spin up to build boost, then the gate starts to open and bleeds off pressure to control the exhaust. But the longer you stay in it, the more heat you are putting to the turbine, this is a cumulative effect (ever notice your pipes glowing after a long run?). The gate is constantly opening more and more to waste more exhaust. So by the time you get to the top of second gear lets say, the gate is fully open and cannot waste any more exhaust. The longer you stay in it after this, the more the boost is going to increase. Obviously at some point the turbine will reach its maximum temperature when it rejects the same amount of heat putting into it. The more ineffective the gate the more pronounced this condition, which is called boost creep. Nonnie's is a pretty extreme example. Most people will see a few pounds and thats it? Why? Because most people arent in it long enough to get that steady state condition, and their gates are "effective enough" to give them what they want.

I am sure you know most of this already, but most people dont, which is fine, because thats what forums are for, right?

I agree with you that electronic boost controllers are nice, but there is nothing wrong with springs. In fact, springs should be the primary method of controlling boost, and a controller to merely modify the springs behavior.
The comment you made earlier about bp not effecting the wastegate...this is incorrect. If you dont have reference lines hooked up to wastegate, how does it work at all? The pressure in the exhaust pushes the valve open. All EBC's do is either add pressure to the top, or to the bottom, to modify when the valve moves. Essentially adding or subtracting effective spring pressure.

This is where an electronic boost controller would come in handy, because most of them have a "gate pressure". Which is, when it should start helping open the gate. See gates using just springs have pressure at which they start to open, and a higher pressure at which they are fully open. Most springs are rated by their fully open pressure, but that doesnt tell you the whole story. A 10psi spring will be fully open at 10psi, but might start opening at 4psi. This is how boost controllers improve spool time...they keep all the gases going to the turbine until desired boost is reached then snap the gate open suddenly, whereas just a spring will slowly bleed off more and more gas until the pressure on the bottom of the valve (exhaust bp) equals the top (spring).

So to you situation, you can do 2 different gates with 2 different springs, but it will not work exactly like you described. The 6lb spring will be a little less than 6 and the second gate with the 10 will be slightly less. If you dont use a boost controller, you setup will be laggier. However, your bp ratio will be better, so your upper rpms power will improve. This essentially is the same thing as going to bigger turbine housing. Yes 2 gates will control the boost better, but it will take a lot of tweaking to get it where you want.

 

I got mixed up a bit with Choda and Nonneidelman builds.

Nonneidelman: I googled your kit to check it out... I can see why your having problems with the system. They must not have did much R&D with this before release. Doesn't look to be that hard of a fix considering how hard it can be to remove turbo kit components on other vehicles. You can drop the crossover pipe and have a larger wastegate flange installed. Highly recommended not to run on the cutout until you can keep that boost in check

Choda: Shot a few questions your way thinking you was having the 25psi spike. Your situation is common and expected. Opening the cutouts you get better turbo efficiency and ride a few lbs higher due to it being spring controlled. You've got plenty of wastegate capacity seeing it's not spiking like Nonneidelman

Atomic:

I was refering to back pressure as in the discharge side of the turbo, Not exhaust manifold pressure (BP). So yes I agree with what you posted earlier, I think we were looking at the different sides of it. Like it mentioned to Choda I'd got him crossed up, I had to go back and reread the entire thread lol.

 

I talked to my tuner today and he said to keep the 8 lb spring in there and after my supporting mods are installed and tuned ( trans, conv, injectors ) open the cut out and see how much boost increases. If it stays at 11 and is usable power then I'll keep it as is and will only have max power when i want it w the cutout open. I'll keep u guys updated

 

I built his kit. Trick Performance kits (the builder of the OP) have the WG in the crossover, just like mine. Together, be have HUNDREDS of these kit's out there, just like this. The WG works just fine there 95% of the time. There is the rare location, where flow dynamics of the pipe, turbo, and tail pipes work out just wrong and there is some difficultly controlling the boost. But you will have that, just as Atomic does with his setup and the WG right under his turbo.

I have one of my kits on my DD in my sig. With my combination, I actually have trouble getting the actual rated spring pressure out of the setup. I have to stack a 7 and 10 psi springs to get 13psi with the WG closed and 15 with it open. I now have just the 10 psi spring in it and only get 9 on the spring and use a manual controller to turn it up to 15 when I wanna play.