Cam overlap through the midrange question

[hjtrbo]

Question though for someone willing to give up some info, please look at my screenshot where I have circled and drawn a flat yellow line. Notice a reduction in my rate of acceleration. It also coincides with a dip in the cam overlap. This area of both cam tables is bone stock. Would you normally adjust the overlap to get a straight line through that area like I have drawn? Obvious answer is test but I've only got the road dyno and the weather is atrocious here at the moment so wont get to test for a few days.
Comments much appreciated. (Cross posted on PCMTEC forum also)

[smokeshow]

Also looks to be a little wiggle in the boost there. Although, this is the non-ecoboost forum. What vehicle is it?

[hjtrbo]

Hey smoke!

It's an Aussie Ford FG XR6 Turbo ute. Inline 6 4.0L. Running open loop boost. Very new to Fords, turbo charging and variable cams so I have lots to take in. If you care to enlighten me about the flutter, what should I be looking for as possible 'typical' causes?

On another note, the boost control setup makes no sense to me. I'll try to explain my head space.

On spool up we hold the boost solenoid shut to build boost. Then when desired boost is approaching we vary the duty cycle of the solenoid which sends a pressure signal to manipulate the wastegate opening thereby controlling the system to some desired level of boost. Everything is fine so far...

At this point we have 'some' level of pressure in the signal line between the solenoid and the wastegate actuator and the system is in steady state.

Now at a later point in the pull, I want to increase the boost pressure (for whatever reason). To do this I ask the boost solenoid to open less. I expect the result to be less pressure in the signal line so the wastegate can open less but there is already the higher signal pressure to the wastegate actuator present from the previous control state. It is effectively trapped and will always be acting on the wastegate. I.e I can never bleed off the signal pressure I used earlier in the pull. Am I on track?

Currently plumbed as per the 2 port image as per OEM.

And looking to try as per attached with a 3 port.

[smokeshow]

Looks like you're right about the solenoid. If that's OEM configuration, then yeah you couldn't let pressure out to raise boost. Though there being an actual wastegate duty cycle in that data suggests something else is going on.

I'd say the dip there in acceleration is in the noise. Likely the little boost spike and gate opening causing a torque bump.

[hjtrbo]

This is the duty cycle commanded for the same run as posted above. Had it scaled in the csv wrong that I imported the log from. I was playing around just seeing cause and effect and that's when I started wondering about the way the factory has it set up.

What are you like with variable cams? And I think you've got a large crowd waiting for you in the Gen 4 section lol.

Cheers, HJ