What kind of values should someone typically see for the Wastegate Control duty cycle percentage?

The reason that I ask is that I've been monitoring it with AutoEnginuity and on my 2000 F450 it's almost always either at 100% or close to zero %. Is that normal?

How is the Wastegate Control duty cycle related to such things as engine RPM, Turbo boost pressure and so on? In other words... when should the duty cycle increase towards 100% and when should it be close to zero %?

 

One would think that there would be some middle ground. I'm interested in hearing about this too.

 

Not really.. at idle it should read 0.00% if you give it a little throttle it should go to around 99.17% (Closed).

Now look at boost (Gauge pressure) as it rises above 5psi the duty cycle should start to go down (Wastegate Opening) a 65% duty cycle indicates wastegate is 35% open.

 

OK, I'm lost. I thought the wastegate was pneumatically controlled off the boost line? Are you guys talking about the EBPV?

Please educate me......

 

Ditto for me. Is there an electronic reading via a sensor somewhere I don't know about?

 

It is pneumatically controlled but its position PID is monitored by the PCM

 

By what means?

 

here is the diagram

 

Crap Alan, you are quick with a diagram. I see there is a wastegate solenoid. Those are usually on or off. It will not activate the wastegate so WTH? Simply a sensor? Then why the name solenoid? Curiously, this solenoid is actually pneumatically activated and therefore a diaphram. I say it's on or it is off.

 

MAP sensor. At ~5 psi the PCM commands the wastegate control solenoind to start to open, it's full open by 8 psi....so it's easy to see how at anything other than that 3psi window the wastegate will either be full open or full close.

 

I'll need to dig to be sure but I believe that the resistance is varied based on boost and interpreted by the pcm. I dont think it is the actuall position of the wastegate

 

Of course not. The wastegate itself is purely mechanical. The PCM only reads the MAP input and WGC solenoid output. It has no idea where the wastegate actually is.....until the MAP goes over 4.7 volts. That the PCM reads as an overboost and defuels.

 

From Dennis at ITP
The Wastegate Control Solenoid (WGCS) is NORMALLY CLOSED...as is the Wastegate Control Valve (WGCV). The WGCS is what we commonly call the actuator.

The RED tube from the intake manifold is connected to BOTH the solenoid and the valve. When there is no current being supplied to the solenoid, all boost from the manifold is allowed to act on the valve to open the wastegate.

The PCM provides a pulse width modulated signal to the solenoid. This signal opens the solenoid (how much depends on the duty cycle) and allows boost pressure in the red line to be bled off into the green line that connects to the inlet of the turbocharger. The higher the duty cycle, the less boost is acting on the valve to open the wastegate.

When you stab the throttle, the solenoid goes to 100% (practically) to hold the WG shut and allow the truck to build boost. As the boost comes up, the duty cycle will drop and begin opening the WG. 65% Duty Cycle would mean that the WG is opening 35% (roughly, I'm not sure that the actual movement of the WG is linear in relation to the % DC)...you get the picture.

 

So it is electromechanical then eh? I will have to inspect that rascal closer sometime. Specifically looking for any wire leads. I don't recall any.

 

That was kind of my point. It is impossible for the WGC duty cycle to be linear wth the WG position. The PCM is not aware of the actual position.

The entire WGC duty cycle happens within that 3 psi window.