Critical Thinking Question (for some)

[Gst18]

So i'm currently done building my custom divided t4 exhaust manifold. I bought 2 used tial 38 mm wastegates. 1 tial has a 8 lb spring and the other tial has a 9 lb spring. If I were to run my car with those two wastegates and those 2 different rated springs what kind of problems will I be looking at? I know its just a 1 lb difference but from what Ive heard it might put stress on the turbine wheel and shaft.

As much as i dont want to do this i might have too just for a couple of days.
Any inputs welcome

 

[BrokenTsi]

I cant think of a reason it wouldn't work. One wastegate will open a fraction of a second faster then the other, but I dont see why it would hurt.

Why not buy a matching spring and then you'll know it will work?

 

[Gst18]

I'd have to wait for shipping either way and i need to have the car running this week.

 

[Gst18]

maybe someone has a 8 or 9 psi spring they might want to trade me?

 

[drivemusicnow]

Are you using a manual boost controller?

Then it doesn't matter. Not that it really would matter at all anyway, but just a more obvious solution.

 

[RayPeters]

You'll have no issues, boost will be 8 psi unless you exceed the flow capacity of the lower pressure valve. Then pressure will be 9psi until you exceed the flow of your second valve. If you reach that point, YDM.

Good luck on your build.

 

[Gst18]

YDM? Not familiar with that.

I always thought the same as what BrokenTsi said, which is that one wg would open a fraction earlier.

When i really think about it one side of the shaft will be recieving 8 psi and the other would recieve 9 psi since im running a divided manifold and turbo( turbine inlet is also divided). So wouldnt one wastegate keep a constant 8 psi on one side of the shaft and 9 psi on the other side of the shaft?

 

[drivemusicnow]

Think about it this way, if you're using an MBC set for over 9 PSI, it will only show the wastegates pressure until after the spring is already "defeated" thus, both will open the same.

Now, if you're not running an MBC, then the one wastegate will open at 8 PSI, and only if you manage to out flow that 1 wastegate and start to run more than 8psi, ie 9 psi, then the other wastegate will open.

Either way, you're fine, and you won't have a problem.

 

[Gst18]

so then i will be dumping out of 1 wg until excess pressure will cause the other wg to open. (somewhat like a reserve wg) to protect against spikes.
This makes me wonder about performance. If it will only be dumping off of one side of the manifold (ie #2 and 3 runner) then wouldnt there be some kind of performance loss or not?
Now that i think about it probably not because its excess exhaust flow thats not needed anyway.

 

[aero_sallee]

It won't hurt anything as others have said. There are people who have blocked off or installed flappers to block one side of a divided flange TH to help spool. I haven't heard of any issues with turbo wear from them. Your 1lb difference wouldn't be anything near what they are doing. It doesn't seem uncommon for people to run a WG off one side of a divided flange. Also the internal gates on divided flange turbos vent from one side only.

 

[Gst18]

thanks for the replies. Makes better sense now.

 

[GVR4592]

You'll have no issues, boost will be 8 psi unless you exceed the flow capacity of the lower pressure valve. Then pressure will be 9psi until you exceed the flow of your second valve. If you reach that point, YDM.

Good luck on your build.

That's not the case with a divided manifold.