GM wastegate operation

**Superbee** · 03-26-2017

Hello guys, I have issues with my boost control. Here is a quick rundown of what i have and what my issue is,

I have 2.0 turbo sunbird. It has an external wastegate on it now with rock solid boost at whatever wastegate spring i choose.

Right now I put a 5 psi spring in it.

Hook the boost solenoid up with METAL port to a vac Y that goes to turbo compressor housing and wastegate BOTTOM port..

Vent port of solenoid has the factory foam on it. Other port goes to TOP wastegate port.

Electrical connector has 12V going to side of wastegate solenoid that has the ( + ) inscribed in it. Other a ground. (factory connector)

ISSUE: 99% duty cycle allows spring pressure boost.

0% duty cycle allows for ALL the boost until I let off.. This is exact opposite as it should be. which is why Ive got crazy boost issues when trying to use a factory electronic setup.

WHY WOULD IT BE DOING THIS???? I cant explain it. Obviously if i set it to say 50% DC, the car will hit my desired boost and then it may drop off a little so the ecm will add more DC, which causes the boost to drop off more, which causes the ecm to go to 99 soon, and im riding on spring pressure 5 psi....

Car off, i can blow through solenoid through the turbo side vac hose....start the car and its blocked..

I dont get this.

Dont think it matters but Im running $59 code59.

**1project2many** · 03-27-2017

The boost solenoid plus ecm control is a sophisticated way to trick the wastegate into operating differently than built. When the solenoid is "on," boost signal from the engine or compressor is vented through the solenoid at the metal port to atmosphere through the foam keeping the pressure at the wastegate low and allowing boost to build. The wastegate is isolated from the signal and atmosphere. When the solenoid is "off" the wastegate is exposed to signal pressure. This allows wastegate opening to be delayed until desired pressure is built. It also allows for boost to be controlled if the ecm is unable to control the solenoid. Boost is always directed to the wastegate with no venting.

In your system the compresor signal is connected to the wastegate pressure signal sense port. The signal is also Teed to the boost solenoid which can either vent it to atmosphere or connect it to the spring side of the wastegate to delay opening. When the solenoid is not connecting boost signal to spring side, any pressure in the spring side of the wastegate is sealed off from atmosphere and from wastegate signal. The effect of this is you have spring pressure plus any boost pressure trapped in the spring side and no way to vent it.

You have a couple of options. The first is to use your wastegate like the single port version and leave the top port vented to atmosphere. The system will work like an OE Sunbird system with the ecm venting boost signal to trick the wastegate. The other is to try turning the solenoid around. This will permanently connect the boost signal to the pressure sense port on the wastegate and will allow the top port to switch between atmosphere when the solenoid is off and the pressure signal when the wastegate is on. This will limit max pressure to spring pressure if the solenoid isn't working and will allow you to use ecm control to increase boost as needed. You will probably need to experiment to determine the best control settings for this method. One advantage is that if you get it worked out, this approach may result in no boost flare or creep, a problem common with the stock Sunbird and with the SyTy.

**Superbee** · 03-27-2017

In the car now... Just switched the two lines going to the solenoid.. I.e. the steel port and port that doesnt have the filter.... Now the car has no boost control wither the dc is set to 0 or 100... Just goes higher and higher.

**1project2many** · 03-27-2017

What is controlling solenoid? Ecm? Is steel port connected to wastegate top port?

**Superbee** · 03-27-2017

Tried steel port to top of wastegate. Plastic port to source "T"

Just now i tried source T to steel port only of solenoid and left top WG port open. That didnt work.

Then i went turbine housing to steel port of solenoid. Plastic port on solenoid to bottom of wastegate... With that setup, 0 duty cycle makes boost hang around 10 or a little more with target set at 7.. 99%dc makes it climb to whatever