Exhaust VCT ON/OFF Cycling Normal? (Data Inside )

[Weyland-Yutani]

I’ve got an issue where there’s a distinct vct timing on-off cycle under a light load. It occurs when the cylinder head is >190° and when under a light load. The conditions for the graph attached is cruise control set at 45 MPH, about 2750 RPM, in 3rd, and shallow rolling hills. The on/off cycling happens just as you begin up a gradual hill. (2018 GT w MT)

There are no codes and it may be perfectly normal, but you can definitely feel/hear it. It doesn’t seem right and it also creates very light knock. I logged the VCTs expecting to see jacking around because of a big following error, but the opposite seems to be true. The cams actually follow pretty good. The exhaust vct solenoids are being commanded on/off every second or so under light load.

So….that seem normal?
What else should I log?

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[engineermike]

On the exhaust side, 0 duty cycle sends the cams to the fully advanced “home” position. I didn’t open the log to see, but did you log “vct schedule”?

Is the car tuned?

 

[Weyland-Yutani]

On the exhaust side, 0 duty cycle sends the cams to the fully advanced “home” position. I didn’t open the log to see, but did you log “vct schedule”?

Is the car tuned?

I don’t see that in the list. Everything else vct related is like delta values, duty cycle %, and “status” (which I assume is like good/not good). I’ll look for it though and run another log.

The car is factory tune. The only “mod” is a cat-back.

 

[Pistol_91]

Can't really determine anything without logging actual load and vct schedule to see which tables its using. But you can assume normal operation, looks to me like it is going from light load (coasting or going downhill a bit) to moderate load (going up a hill). The stock tune has the cams changing quite a bit between RPM and Loads.

A good test would be on a completely flat road and see what it does then. Any time loads are going from .2 - .6~ there is going to be a bit of changes happening.

Here is a screenshot from a 2019 GT. These are the 2 tables it uses while cruising. You can see it blends between possibly 5 or so mapped points in that small range you're in.

Looks totally normal.

 

[Weyland-Yutani]

I’ll add load on the next logging too.

What do the values in the chart represent? Like, in “Best Drivability Distance” 2500 RPM at .75 Load is 8.97. What is that 8.97?

 

[Pistol_91]

I’ll add load on the next logging too.

What do the values in the chart represent? Like, in “Best Drivability Distance” 2500 RPM at .75 Load is 8.97. What is that 8.97?

It refers directly to the table to the left. Which then point to whatever number is inputted there. That number is the "mapped point" it's using.
So 8.97 would be blending mapped points 8 and 9. The value being 8.97 is close to 9.00 so it is almost using 100% of mapped point 9.
Each mapped point has different cam angles. They're basically cam angle maps. So you can see they're blending quite a bit along the entire table.

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