Too big BOV?

[rolltidero]

On my car I have the stock t25 turbo and a turbo xs BOV. When I took it in the guy at the garage tried to tell me the BOV was too big for the turbo and could possibly blow my turbo because pressure wouldn't be relieved from the turbo. I thought that the wastegate would do that not the BOV. Is it possible for a BOV to be too big and if so is this one too big?

 

[bryanwheat]

He is full of it. First off it is really impossible to have too big of a valve. All it does is release pressure from the system when you remove your foot from the throttle. It in no way could hurt the turbo. Another thing to consider is even though it is physically larger than the stock bov, the size of the piston and exit tube are relatively close in size so the valve itself is very similar. It is also going to be be better for the turbo to have a bov that actually seals under boost. The stock 2g bovs leak after 10 psi on most setups which means that the turbo is working harder to keep the pressure up.

 

[Archer Fabrications]

Are you recirculating it? If it was too BIG, how could it not releave enough pressure? Lol

Yes the wastegate is what controls boost and not the bov.

I dont think theres such a thing as too big per say. But if your stock you need to have it recirculated into the intake, and if yours doesnt do that you need to buy one that does. The blow off valve only releaves pipe pressure when the throttle plate is closed so the turbo doesnt try and surge.(not boost related)

 

[codym]

Basically, the BOV opens when the throttle plate is closing to prevent the turbo from surging, so long as the spring in the bov is correct and the bov is functional, that will be operational.

Tial does not offer a 7psi spring with the Q BOV, only the old style 50mm. You want to run the lightest spring possible thats in your vacuum range.

-8 to -11 in/HG use 6 PSI Spring (Black)
-12 to -15 in/HG use 8 PSI Spring (White)
-16 to -19 in/HG use 10 PSI Spring (Silver)
-20 to -21 in/HG use 11 PSI Spring (Purple)

The wastegate opens to channel air away from the turbo and back into the exhaust, when the wastegate opens is what controls how much pressure get's introduced into the intake system.

 

[rolltidero]

He is full of it. First off it is really impossible to have too big of a valve. All it does is release pressure from the system when you remove your foot from the throttle. It in no way could hurt the turbo. Another thing to consider is even though it is physically larger than the stock bov, the size of the piston and exit tube are relatively close in size so the valve itself is very similar. It is also going to be be better for the turbo to have a bov that actually seals under boost. The stock 2g bovs leak after 10 psi on most setups which means that the turbo is working harder to keep the pressure up.

I tried to explain that. I thought only a wastegate being too big could really damage the turbo because it wouldn't open and divert the exhaust gases around the turbo and in turn over spool and blow it.

 

[bryanwheat]

I tried to explain that. I thought only a wastegate being too big could really damage the turbo because it wouldn't open and divert the exhaust gases around the turbo and in turn over spool and blow it.

That isn't really even true. The bigger the wastegate, the more gasses it will be able to divert around the turbine. The wastegate is opened with pressure from the compressor side of the turbo, so it will still open when a certain amount of pressure is present in the source line.

 

[rolltidero]

That isn't really even true. The bigger the wastegate, the more gasses it will be able to divert around the turbine. The wastegate is opened with pressure from the compressor side of the turbo, so it will still open when a certain amount of pressure is present in the source line.

Ok thank you for clearing that up for me. Now I just have to call the guy and tell him not to replace it. He was saying he'd find a stock one for me and put it on and wouldn't listen when I told him it was fine.

 

[Steve93Talon]

A recurring theme here is that people need to stop taking their cars to regular mechanics, they typically don't seem to know anything about modern performance cars, especially with forced induction. Hopefully threads like this will encourage more people to learn to do their own work.