how much boost can wrx wastegates hold?

[Sin'sVr4]

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I know my stockers were good up to ateast 22psi. I was told they will collapse around 25psi. I just got some wrx becasue i was told tehy can handle more. I want to run 25-28psi. Will these be okay?

[Sin'sVr4]

anyone have a clue?

[JasonY]

I think they are 9lb springs, so they may have a little more overhead vs our stockers.

Jason

[RealMcCoy]

Too many variables to say without having personal experience.... If you find someone with a TD04 that's blown open a WRX spring wastegate, let me know...

If you have the stockers apart to change the spring, there's no reason not to throw a shim in there to preload it a bit. I used an appropriate size fender washer, My wastegate boost is now 11.5 psi.

That's almost double the spring pressure on the gate, so it would take almost double the exhaust housing pressure to open it.

[GTOJOE]

Just buy the Forge Billet ones and be done with it

[J. Fast]

Too many variables to say without having personal experience.... If you find someone with a TD04 that's blown open a WRX spring wastegate, let me know...

If you have the stockers apart to change the spring, there's no reason not to throw a shim in there to preload it a bit. I used an appropriate size fender washer, My wastegate boost is now 11.5 psi.

That's almost double the spring pressure on the gate, so it would take almost double the exhaust housing pressure to open it.

Do you have any problems with spiking with the modifications? When I ran into the stock collapse issue/limit... I tried a helper spring first and then a shim modification. The shim resulted in some really scary boost spiking. It was really stable in cruise and midrage but when you opened it up it would spike 4-5psi over my setting. That was very problematic. On several occasions I was expecting to see 24psi and ended up getting 28-29psi. I was very lucky to have my AEM knock control engaged because the spike literally killed the engine. On several occasions I had to pull over and kill the car and restart it since my recovery settings weren't cooperating at highways speeds.

I would have to say shimming is something you should proceed with caution on. The end result can be unpredictable depending on the VE and exhaust design. The effects of spike will vary based on wether you're running cats, pre-cats, no cats, 3", 3 1/2", or 4" exhaust as well.

A crapload of Subie guys (awdpirates) here in Colorado are notorious for shiming wastegates. From what I've read and discussed in person with others, tradeoffs exist. The subie guys I've personally discussed the issue with mentioned they also have encountered boost spikes once they jack with the spring. When they preload the spring to up the boost they lose some control and there turbos also spike their wastegates also start to flutter in the lowrange with the preload mod.

[RealMcCoy]

I'm trying to wrap my brain around what possible difference there would be in preloading a 9lb spring to add 2 lbs, or a dedicated 11 lb spring... I can't see it. Obviously there's variations in spring rates that could come in to play, but that could be said for any set of springs. you could easily have two very different spring rates and lengths start to open at the same pressure, but need different pressure to be fully open.

I wonder if a lot of people that have issues with shimming aren't limiting the travel of the gate when they do it..? I basically removed the stock spring, installed the WRX spring, and added a shim under it to increase the preload a couple lbs. I then installed and adjusted the actuators just like the stock ones.

I haven't had any spiking issues, but I'm only running 16 psi at the moment and a manual boost controller. We'll see what happens soon when I get the water/meth hooked up and the electronic controller installed.

I guess the real test would be to drive the car on wastgate boost and see if it stays there... If it spikes above wastgate boost, then I would say there's a problem, If it's able to keep it at wastegate boost at all times, then any problems above that are simply boost controller issues.

[Sin'sVr4]

Mcoy, im not talking about running that little of boost. Im talking in the 25+ range. I was ok at 22psi, but i want to raise my psi thats why i went with the wrx. I was just wondering who has run these over 25+ psi. thats all. J i should be fine right?

[RealMcCoy]

Mcoy, im not talking about running that little of boost. Im talking in the 25+ range. I was ok at 22psi, but i want to raise my psi thats why i went with the wrx. I was just wondering who has run these over 25+ psi. thats all. J i should be fine right?

I'm fully aware of what you intend to do. You have no call to discredit what I'm saying because my car has the boost turned down... I only mentioned it to respond to J's question about my personal experiences. I usually get ignored when I tell people things they don't want to hear, not used to getting it for telling someone what they do want to hear....


The point I was trying to make, is that you won't find anyone with a TD04 that's blown open a 9lb spring. It's not about how much boost you're running, it's about the back pressure in the exhaust housing. That's going to vary with setup, but eventually come down to the TD04 housing being the choke point. If it takes 35 psi exhaust backpressure to blow open a 6 lb spring (no claim of accuracy on the numbers, I just pulled 35 psi out of my ass to make a point) sixth grade math tells us that it would take 52.5 psi to blow open a 9 lb spring, and 64 psi to blow open an 11 lb spring...

If you assume a linear correlation between boost and exhaust pressure (not true or accurate, but we'll do it for easy math) your 22 lb limit with a 6 lb spring would be upped to 33 lbs with a 9 lb spring, and 40 psi with an 11 lb spring.

[Sin'sVr4]

right on. sounds like a plan. J told me his stock collapsed around 23-25psi. so i wanted to be safe and just go with wrx for that extra 5-7 psi boost.