Boost Controller Gate Pressure

[GNDriven]

Guys, How much gate pressure does it take to make 32 psi?
I think I have a 8psi spring. Engine is stage II 274".
Thanks

 

[TurboBob]

at least 24. it depends on how high your backpressure is, the kind of wastegate, and the plumbing details.

Bob

 

[NY Twin Turbo]

To have a 'no move' condition on the wastegate, theoretically there will be the same pressure on both sides or more pressure under the diaphragm. But on one side is the spring holding it closed. This is a certain amount of preloaded pressure that needs to be added to (usually with intake boost pressure) in order for it to equalize. But still it wont open. Because then of course, it will need a even more to overcome the exhaust pressure pushing up against the tulip valve in the wastegate. Pressure allowed to escape under the diaphragm will help the pressure above it push through the spring pressure and allow it to open.

I'm not even sure I get it sometimes
If I'm off, someone will let me know.

 

[TurboBuRick]

But still it wont open. Because then of course, it will need a even more to overcome the exhaust pressure pushing up against the tulip valve in the wastegate.

My understanding is the exhaust back pressure against the gate valve works to push the gate open.

I would agree with Bob. If one has a 8lb spring and and wants 32lbs of boost, simply add the difference to the opposing side of the gate. But like mentioned there are a few other things to factor in. Ultimately a few more pounds of pressure will prolly be required to hit the target.

 

[turbobitt]

There are too many factors to get to a specific number. Backpressure being one of them and also the surface area of the gate. I have what I would consider low backpressure and I still need 30 psi to the gate to make 30 psi boost with a 15lb spring.
AG.

 

[GNDriven]

OK just making sure there wasn't any fuzzy math or sideways thinking I needed to do here. Reason I am asking is I am looking hard at the MSD boost controller 7763. I have the MSD power grid setup. They have two models out. 1 uses two 45psi (4-bar) internal map sensors to measure gate pressure and manifold pressure. Price = $450. Another unit MSD 77631 uses two external 75psi pressure sensors to measure and log gate pressure vs manifold pressure. Price = $800. So .. Just trying to make the best decision here. It is def time for a boost controller. Like I said I have the power grid setup, and both of the units will use the graphs and control interface that the power grid employs.

 

[NY Twin Turbo]

My understanding is the exhaust back pressure against the gate valve works to push the gate open.

I would agree with Bob. If one has a 8lb spring and and wants 32lbs of boost, simply add the difference to the opposing side of the gate. But like mentioned there are a few other things to factor in. Ultimately a few more pounds of pressure will prolly be required to hit the target.

Yes. You are correct. I forgot the valve lifts not drops. That reverses what I said earlier.

 

[GNDriven]

Does anyone have any experience with the MSD boost controllers. I find very little forum activity about the MSD stuff on the general web searches. I know Boost Leash and AMS have the captive audience (prob for good reason), but the power grid makes everything inclusive.

 

[turbobitt]

I always for stretching the dollar so in my opinion if your in the market for, or already have an XFI than should try that first.
AG


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[GNDriven]

I have the classic FAST. So I don't have that as an option. Although, it might makes since to upgrade.

 

[turbo nasty]

See what your back psi is first

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[GNDriven]

See what your back psi is first

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I think you are right TurboNasty.

Regarding back pressure, Turbobitt, can you provide a back pressure psi with that 30psi on the gate to make 30psi in the intake manifold?

 

[turbobitt]

I think you are right TurboNasty.

Regarding back pressure, Turbobitt, can you provide a back pressure psi with that 30psi on the gate to make 30psi in the intake manifold?

About 45 psi but I also use a heavy spring and get 15 psi boost without adding pressure.
AG

 

[forcefed3.8's]

With my 7675, it took 36psi to make 31psi. This is with a 4lbs spring. I will find out what a 6870 and 7168 3 bolt take in a few weeks.