I really don't think its any harder or easier than any other turbo with a WG actuator. Tap the elbow in the boost reference line and adjust the screw until your boost maxes where you want it. Not much more to it than that.

Since the controller is working and there are no codes, pinching the boost reference hose increase the boost, it HAS to be the actuator. The actuator are a LOT harder to remove\replace than a boost elbow, thats my view.

Then when he gets tired of the electronics getting in his way its already fixed.

 

Its just harder (ive looked and haven't found one, well a small one) to find a adjustable elbow that has hose barb on both side, you can't screw one into the HE351 without drilling and tapping.

 

Ummm, get a barb that fits the threaded end and problem solved. No drilling needed.

 

Well yeah... there is that option :-)

If the actuator is failed enough thou a adj elbow won't fix the issue without blocking the line of compleatly, and then boost will still get to high and possibly cause an overboost code..

I guess I prefer to fix a broken part than to bandaid it.

 

Ah but it isn't totally broke becuase he can still make 20 psi of boost when the boost line is open. The actuator is out of adjustment, the spring is getting weak, or ??? The actuator is a simple diaphram with a spring behind it to hold the WG closed. When boost overcomes spring pressure the rod moves and opens the WG.

Would'nt you think if the thing was completely broke it would only see minimal boost?

You are right, replacing the actuator is the correct way to go about it. That just looks like a PITA to accomplish though.

 

But is the command valve open at all below 20 psi?

22-24 psi is about what a boost fooler shows the ECM, which shouldn't have any air going thru the command valve. So my thought is that as soon as the command valve is being signaled to provide some air the WG actuator can't hold back any more and opens, thus limiting boost.

What I don't get is that if the WG spring is weak why doesn't drive pressure force it open at low pressues also? It doesn't make complete sence that the actuator is failed, but will still hold back against 50+ psi of drive pressure and make 40 psi of boost.

So I guess I am still at a loss. But personally I'd still go thru the pain of an acutator replacement. If that doesn't do it, then no friggin clue.. Its something in the ECM or command valve (new part).

 

Yup, I don't get that either unless its a mechanical advantage via a lever on the actuator.

 

Wish I had read this post before! Mine read right about 12 psi with engine off or at idle (I live @ 4600 ft elevation). Thinking it bad I replaced it, about $83 from Cummins, the new one reads the exact same numbers. Boost guage shows 12 psi less than scan tool accross the entire RPM range.

Great info guys! Thanks for some of the most comprehensive tech posts I have ever seen on these forums.

 

Sounds like a perfectly normal reading for 4600 feet ....doh!

 

I've read this thread and I'm a bit confused. I'm also curious to know how this sucker works, so bear with me here.



I'm used to a traditional 'boost controller' which bleeds part of the boost signal to the wastegate, thus lowering the boost the wastegate actuator sees. Boost output increases as the bleed is opened up more. It can be a manual device (boost fooler) or an active device like a digital boost controller.

The wastegate actuator has a spring which holds the wastegate closed and a diaphram which opposes it, so that when the pressure reaches a certain level, the wastegate opens to regulate the turbine speed, and therefore the boost level.

So, is the electrical solenoid a bleed, or is it inline with the pressure signal to the actuator? This is critical to figure this one out.

If its a bleed, one would expect it to be open until the the correct boost is reached, then close to apply pressure to the wastegate actuator which will open the wastegate when the max boost is reached. The solenoid is a pwm (ie: variable) valve to avoid an on/off situation.

OR

If it's inline it would be closed until max boost is reached, then start to open to allow pressure to the wastegate actuator



In the underboost condition with a bleed, I'd look for a wastegate actuator with the spring worn out...allowing the wastegate to open with less than mx boost

With the inline situation I'd look for a stuck open solenoid valve, or perhaps a busted ecm (if energized keeps it closed as previoulsy written), or a busted diaphram in the actuator.

If it's the inline situation and you want to determine what the ecm is doing, you can connect a DC voltmeter to the solenoid input. 100% duty cycle = 13.x volts, and 0 duty cycle = 0 volts.

Because you pinched off the boost source to the actuator and it made good boost, I don't think you have a bad actuator spring. Because you let it go and you had low boost I suspect your actuator diaphram is fine along with your tubing etc.. That only leaves the solenoid and ecm.

Chay

 

The OEM solenoid does both, bleeds back to the intake of the compressor and feeds pressure direct to the traditional wastegate.

The solenoid will modulate between closed and open to provide the desired boost level and is commanded by the ECM.

 

That makes sense; otherwise the pressure would be 'trapped' between the solenoid and actuator.

This would lead me to believe that it's very likely the solenoid sticking in the 'overboost' position, or ecm not driving the valve properly. My experience is that ECMs rarely go bad. Mechanical devices go bad all the time.

Probably the bleed is a fixed value and the feed changes....could be vice versa I guess. Maybe even both if it's fancy eh?

Chay

 

The solenoid contains a moveable valve that opens and closes the feed port to the actuator based on a PWM signal. When its in the centered postion the actuator is open to compressor side. As the boost increase that is blocked and boost is applied to the actuator. Depending on what the spring pressure is and the rod set at, 20 to 26 lbs of boost to overcome the spring.

When the contoller goes bad or its unplugged it defaults to full boost to the actuator. It has to energize and center to close off the actuator port. The ECU calculates boost based on values from the baro sensor and MAP sensor and constantly sets the controller solenoid based on those readings.

 

mine is doing the same I cant make boost over 25psi unless i pinch the line. Will it hurt to leave the line pinched off.

 

Depends on how much restraint your right foot has. Mine is going on 2 years crimped closed and it still makes 40 psi with ease.