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Discussion Starter #1
Is there any rule of thumb when using a manual boost controller with an external wastegate? (eg. You souldn't exceed 2x the psi rating of the spring.)
 

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Ive always used a manual.

Im using one. Its a Joe P. MBC ball and spring type. I have a tial 38mm wastegate with an 8 or 9 psi spring, and yes the turbo does spool faster with a boostcontroller. With the boost controller set as low as I can go its like 10 or 11psi. I never tried to run it off the wastegate only. I run 15-17psi. Everyone I know says the same thing with the spool up.

Im not sure if I have an answer for you though. all I can say is get the lowest spring if you want to run the lowest boost without a boost controller. I dont see why you couldnt get a 5 psi spring and run 10 or 20 psi with a boost controller though.
 

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Discussion Starter #5
Currently I have a .7bar (10psi) spring in my Tial 44mm ext.gate. (also have a .9bar (13psi) spring laying around). The car is going to be running approx 1.4bar (20psi) may be a bit more). Now if I only have a .7bar spring and 1.4 bar is being pushed against the valve causing it to open too soon slowing spool, or not even be able to make the higher target boost. In theory anyways.

With the electronic controllers a press. signal is supplied to the top port on an ext. gate. But with a manual controller this is not the case. So there is no
other force keeping the gate closed other than the spring.

This is why I looking for info from those that have experience with using a manual controller on a external wastgate.
 

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I use a manual on an external gate but do not have the answer for you. I don't recall ever seeing a thread that addressed whether the amount of boost run would have an impact positive or negative dependent on the spring used in the wastegate. Sounds like a good question for Tial.
 

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I have read the same thing: 2X the wastegate static pressure. The logic for this does make sense to me. However, I haven't had the chance to verify this yet, as all EWG cars I see have EBCs.
 

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I've noticed with my TwosRus Manual controller, the wastegate starts to crack open at ~10 psi, even though I have it set to 14.5. Is there any reason for that?
 

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Discussion Starter #9
pentaxis

This is exactly what I'm trying to avoid.
It would make sense to me if your wastgate spring is not strong enough to
resist the pressure then it would start to open.
Are you actually hitting your boost target?
 

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pentaxis said:
I've noticed with my TwosRus Manual controller, the wastegate starts to crack open at ~10 psi, even though I have it set to 14.5. Is there any reason for that?
That is one of the disadvantages MBCs present. The wastegate usually starts to crack open at ~1/2 the boost setpoint. This is a normal behavior, and it's why EBCs produce faster spool on many occasions.
 

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Discussion Starter #14
Also contacted Hallman boost controllers and boostcontroller.com and
got no response also.

Seems to be a mystery.
 

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flyboy said:
That is one of the disadvantages MBCs present. The wastegate usually starts to crack open at ~1/2 the boost setpoint. This is a normal behavior, and it's why EBCs produce faster spool on many occasions.
I ran 16psi and boosted 10 psi and didnt hear my wastegate opening. Now running 17psi btw. I guess I wont be a believer in EBC's until I magically get one for free.

I can also hit 16 or 17psi in 1st gear with my mbc and my bigger than stock turbo.
 

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You must have an open downpipe. I have never heard the exact point the wastegate cracks open unless I'm on the dyno standing right over it.

I'm not trying to sell you on anything. If you want to stick with your MBC, then mazel tov. It's all EBCs for me, however. (I have a Nemesis with the built-in EBC.)
 

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Discussion Starter #17
I have a open external gate, you can definatly hear when it's open. :(

There smees to be no definitive answer to my question.
I guess there is only one way to find out.
 

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Discussion Starter #19
Will do but won't be for some time.
I'll be waiting to get a RMR intake manifold in first, retune then 20psi here I come.
 

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You can only get 2X the boost pressure produced by the spring alone, by adding a boost controller. I've seen it in practice, and it's a generally known rule of thumb.

Supra owners with large single turbos typically run an 18PSI spring in their EWG, in order to be able to hit over 30PSI on their race gas setting.

The reason that the wastegate starts opening before the preset boost level with an MBC is inherent to the way an MBC works. You are using a spring to hold the gate shut on one side, and restricting the air that is pushing against the other side of the spring in order to hold boost higher than the spring rating. It takes a certain amount of force to push open the gate against the spring pressure, and in order to exert this force, the MBC gradually allows more and more of the air signal through, in order to have the gate open at the prescribed boost level.

An EBC works in a completely different manner, by adding air to the same side of the wastegate that the spring is on, to help hold the wastegate shut against the air coming in through the side port, that is pushing against the spring. This means that once you are running more boost than the spring alone supports, the valve is operating on a pressure differential (like the stock and HKS BOV's do). With the pressure differential, the wastegate stays closed until almost the preset amount of boost is reached, because it only takes a small amount of extra pressure on the bottom to pop the valve wide open, and that can happen very quickly, compared to pushing it open against spring pressure.

Ken
 
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