Wastegate control pro's and con's

[jeff1234]

What is the downside of controlling the wastegate by running the vac/press line directly from the turbo to the wastegate instead of controlling it through the wastegate solenoid.

[contraption22]

The downside is lowered boost, unless you increase the spring tension on the wastegate.

[Vigo]

You'll be stuck with minimum boost unless you interrupt that pressure signal with something else like a manual boost controller. Depending on how worn out your wastegate spring is, you'll typically get 5-7psi max, but i've seen as low as 3.

[going4speed]

The question would also be why do you want to do this?

I do this because the car cant control its own boost so I grainger it to get the desired boost.

[jeff1234]

Some who should know told me this is the way he does it so I am checking because to me it seemed that if you take the computer control out it would cause excessive pressure at the wrong time. My wastegate will hold 22 psi.
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My goal is to go to 15 psi max boost with stock CSX chip, without detonation problems. What is the best way to do this.

[contraption22]

My goal is to go to 15 psi max boost with stock CSX chip, without detonation problems. What is the best way to do this.

The best way to do it is with a custom chip.

[ShelGame]

If your wastegate doesn't open until 22psi, then you will never be able to control the boost to 15psi.

[jeff1234]

It controls it at 12 psi right now, why not 15 psi.

[ShelGame]

It controls it at 12 psi right now, why not 15 psi.

If your wastegate doesn't open until 22psi; How can it control the boost to 12psi? Computer controlled boost can't amplify the boost signal. If your wastegate can is set to open at 22psi boost, then your minimum boost will be 22psi. That's why the factory cans are set so low (~7psi). Your WG Can pressure will also be your fail safe boost level (IE, when the solenoid fails).

Using computer controlled boost for higher boost needs a lot of consideration. It's not just a matter of raising the targets. Often, you will have to adjust the WG open pressure, and possibly the plumbing or even the solenoid itself. Changing any of those parts means you will have to re-tune the WG Duty Cycle vs. boost table.

[Vigo]

The wastegate actuator has a spring inside that holds the wastegate puck closed. There is also an air chamber which, when filled to a high enough pressure, overcomes the strength of the spring and causes the wastegate puck to open.

The 'default' arrangement, such as just hooking intake manifold pressure straight to the wastegate actuator, means the wastegate will see whatever boost pressure you are making. On a stock wastegate actuator, 5-7psi is the point where the 'air spring' becomes stronger than the the metal spring and causes the wastegate puck to open.

To achieve boost higher than that 5-7, you have to PREVENT air pressure from reaching the wastegate actuator. The boost control solenoid does this by closing the path until the target boost is reached, at which point it begins to open. Now, if it were to just stay open, your boost would then fall to 5-7. If your boost target is something higher, like ~12psi, you have to feed SOME pressure to the actuator to prevent over boost, but you cannot feed it a sustained pressure over 5-7PSI without just falling to your minimum boost.

To do that, the solenoid clicks open and closed rapidly so that it 'averages' a certain pressure sent to the wastegate can. Why doesn't the pressure just build up over time and end up holding the wastegate open? Because there is a calibrated leak included in the system. Otherwise, the first time your wastegate pressured up and opened, it would stay open forever more until you relieved that pressure. Manual boost controllers include this calibrated leak as well.

[jeff1234]

I really misunderstood what you were asking me. I meant that I was able to hold at 22 psi. Never the less, you have all verified that I was justified in being suspicious of the information I was given. That is the reason that I brought my question to the forum. I had trouble even formulating a question because I couldn't understand how a system that rapidly controlled the waste gate could possibly operate hooked directly to the turbo. I wondered how that would affect how the engine ran and truthfully I didn't realize I wouldn't even be able to get much boost. I didn't know the exact question to ask, however I knew enough to check it out with you guys to find out. This has resulted in better understanding for me and to not trust the info I get from some individuals.
As usual, thanks for the kind assistance you have extended to me, it is appreciated.

One more question, where is the calibrated leak that VIGO spoke of, in the waste gate can? The W/G solenoid vent to atmosphere port?

[cordes]

I really misunderstood what you were asking me. I meant that I was able to hold at 22 psi. Never the less, you have all verified that I was justified in being suspicious of the information I was given. That is the reason that I brought my question to the forum. I had trouble even formulating a question because I couldn't understand how a system that rapidly controlled the waste gate could possibly operate hooked directly to the turbo. I wondered how that would affect how the engine ran and truthfully I didn't realize I wouldn't even be able to get much boost. I didn't know the exact question to ask, however I knew enough to check it out with you guys to find out. This has resulted in better understanding for me and to not trust the info I get from some individuals.
As usual, thanks for the kind assistance you have extended to me, it is appreciated.

One more question, where is the calibrated leak that VIGO spoke of, in the waste gate can? The W/G solenoid vent to atmosphere port?

It's at the solenoid.

[chromguy]

A manual boost controller is easy, but you need to be sure you have enough fuel with a good fuel pump and good quality fuel. Read gus' web info on the use of a manual controller.
http://www.gusmahon.org/html/boostcontrol.htm
I purchased the following from ebay and it is much better than the granger ones I built with very little to no overshoot. I am using 12psi on my 87 TI as my DD for 4 years now
http://www.ebay.com/itm/MANUAL-BOOST...HyY_XA&vxp=mtr

[GLHNSLHT2]

Controlling boost off the outlet of the turbo will also send boost pressure to the solenoid/actuator/manual controller sooner than if it's controlled off the intake. This is good if you have a small turbo you need to keep from overspinning. It's bad though as boost spikes when shifting can cause the boost to fall off more than if it's controlled off the intake.

[jeff1234]

Interesting to see Gus's site back up. In the past many links didn't work so I stopped checking them.

[wheming]

I would add the following thoughts.
I like to use the port on the turbo discharge because the boost signal is the highest pressure. Everywhere further downstream there is some pressure loss (which depends on how good the rest of your system is : turbo plumbing and number of bends, every joint or connector in the system, your pressure drop across your intercooler, and the drop across the trottle). Because for me, i want to make minimum boost at times. If you have a stiff wastegate actuator spring, your minimum might be 10-12psi. I can make my turbo create whatever pressure i want ABOVE the minimum, but i can't make it provide less (without changing the actuator).

The MBC that was posted looks decent, but i would caution using an aluminum housing product, because as the aluminum corrodes, the ball will no longer seal. This is why we started using the brass body grainger valves.
Use Gus' site as a good resource for how to set up switchable boost. I've been using that setup Gus introduced me to for the last 20 years, and still works perfectly. You can have as many as 4 settings with 2 simple solenoids, you can use 2 g-valves and have 3 settings both with quick spooling. Lots of possiblities.

Please note, i am just speaking of the boost control system, you need to be sure your cal and fuel system are properly set up for whatever boost pressure you intend to run with your manual boost control setup.

[jeff1234]

Thank you!