not sure how much boost it takes to set a code but i was letting off when it hit around 40psi. so does anyone understand how the electrical solenoid works to control the wastegate. from looking at it the pin shaped part with the holes in it looks like it rotates to open/close off the vacuum line to the wastegate. so should the wastegate duty cycle as shown on the drbIII increase as boost increases if its working properly and read zero or very low when at idle?

 

The electronic solenoid keeps air from leaving the turbo and going to the wastegate. The ECM applies power to the solenoid to close it under 99% of driving. When your boost hits ~32psi (about 46.7 absolute at sea level, as the DRB would read) it removes the power from the solenoid and it allows air to reach the wastegate. The wastegate itself only needs about 22-24 psi of boost to open, so as soon as the solenoid opens the wastegate opens, which regulates boost. The ECM will cycle the solenoid to allow boost ot stay about 28-30 under WOT no load, and 28-32 under full load.

I am not sure if the valve is a open/closed valve or if it can open partially.

I thought an overboost code hit at about 35 psi, but I am not sure.

By pinching the line (pressure, not vacuum) it doesn't let the WG open and thus you still build boost.

Below about 28psi the solenoid should be fully closed.

 

thanks AH64ID this is starting to make more sense. when driving around with the drbIII plugged in it showed that the ECM was sending more power to the solenoid (increasing the duty cycle) as the boost comes on but for some reason the solenoid must not be keeping the air from going to the wastegate. Boost won't go past 22psi so it seems that the wastegate is opening as soon as is can. Under load and WOT i can get it to 25-27 psi but the wastegate is definetly opening at 20-22psi. And before it was like clockwork spool up to 32psi, wastegate opens and it settles out at 28-30psi.

So if it looks like the ECM is applying power to solenoid and increasing the duty cycle correctly, the solenoid is new, and with the pressure line pinched off the wastegate stays closed, what else should i check? Could there be some build up or a crack in the housing that physically keeps the solenoid from working? Or could the ECM still not be sending the right amount of power to the solenoid?

 

That is not exactly true either. The solenoid just routes boost to the WG actuator based on how far it is opened by the ECU. Its a PWM signal so it does not allow all the boost thru just by opening.

On my truck when the solenoid goes bad the WG acutator opens at 26 psi as read by a manual boost gauge. The WG actuator is what controls how much boost actually opens the WG via a spring and I believe an adjustable rod. More tension and the boost goes higher before it opens, less tension or the spring gets weak and it opens sooner.

From what is posted it sounds like the WG actuator has possibly failed and is opening too soon. Might be worth putting a boost elbow in the reference line and seeing if you can get the boost back that way.

 

When you pinch the WG do you see the DRB drop the voltage when the boost gets to about 32?

 

In a broken system, no its not 100% true. But in a stock system the solenoid (command valve) doesn't open until the boost is above the threashold needed to open the actual WG. Even if it opens slowly there is no escape for the air (like in a adj elbow) so it may be a little slower but it will still give enough pressure to actuate the WG, even if its only 1% open.

Based on watching a DP gauge the command valve doesn't appear to open until 30 psi of boost is obtained, then it opens and the WG opens quite quick.

 

There is a place for air to bleed back to the intake side of the compressor. The ECU sets the position of the controller based on its boost readings and that partially covers the bleed off circuit. As the boost rises the bleed circuit is closed until boost overcomes the actuator spring.

If it did not work like that the boost would be bouncing all over the place as the actuator full opened and closed. Coupled with the actuator only partially opening as boost increases it gives a smoother operation.

Couple of things indicate this is the way it operates. When the controller dies you have a flat cutoff in boost, gauge rises to 26 psi and just stops with no bounce. This is oppsed to stock operation where it would spike to 32 psi then drop to 28 psi then rise back to about 30 psi.

Pretty sure thats why when you add extra fuel with something like the Smarty it will spike to 35 psi then drop back to normal. The ECU does not take into account the extra flow so everything is upped a couple lbs of boost but it is still functioning as the ECU simply sets the solenoid based on a predetermined calculation.

Leastwise, thats the way it works on my truck and what I could tell from playing with settings.

 

Makes sence...

The only way I have to look at it is DP/Boost, and 99% of the time I run the SJR and the WG doesn't work anyhow.. one of the main reasons a new turbo is in the works.

 

is the electric solenoid and the wg actuator the same thing? I already replaced it and no change. am i correct in thinking that since it makes plenty of boost w/ the reference line pinched off that the wastegate and linkage are fine?

 

They are two differnent parts. The solenoid is the one with the electrical connection, the WG actuator is the one that the air line goes into.

 

so is there a way to test the actuator? maybe its time to see if the dealer will replace the turbo under warranty...

 

You can test it with an air compressor. Put air to the feed line and see when it opens.

If your under warranty they should be doing the work for you!

 

Yes they are two parts as AH said, WG controller and WG actuator.

If you can get a gauge and a control on the air line to see where the actuator opens that should tell you what is happening. The boost elbow is just easier to put in and set for your max boost.

 

thanks again guys this turned into a very informative thread! I already had the truck at the dealer for an entire day and all they said was DRBIII showed the WG solenoid was working and that the MAP and IAT sensors appeared to be working and with no codes they didn't have a clue. In fact the tech didn't even know the wastegate should open at 32psi and they told me my boost gauge was off end of story (even though it reads exactly the same as the map sensor).

So am i wrong in thinking that since it makes plenty of boost with the pressure line pinched off that this means the actuator is working ok? and the adjustable boost elbow would allow me to dial in the max boost so it spools over 20psi? kind of seems like band aid fix but if it works i don't care.

 

So the DRB is showing a max of about 34.7?

I would guess its the WG actuator, and would replace it. A boost elbow is much harder to make work on the HE351 due to the command valve.. I would just get a new actuator, even thou it is a little more money.

Amazing the dealership is sluffing you off.