WGDC=0% at cruise, but only some of the time

[ferocity02]

I've noticed that my WGDC will drop to 0% while cruising on the highway (noticeable increase in exhaust sound). But then it will pick back up at random times. There does not appear to be any consistency between when it drops to 0% and when it spikes back up.

What parameters exist in the tune that control this?

Here is a 2.5 minute log cruising on the highway around 70mph: http://datazap.me/u/ferocity02/wgdc-...&data=23-26-28

I don't mind that the WGDC drops to 0%, it's just annoying for the exhaust note to fluctuate so much. In fact, open wastegates seem to boost the highway MPG noticeably. I'd prefer them to stay open unless there is a high-ish load demand. Or at least drop back to 0% right away when load demand is low.

I am running MHD Stage 2 91 octane map.

[jyamona]

Currently you cannot manually set the WGDC to 0% in the tables, as there is an undefined table capping the lower limit. This table will be in the next XDF release though.

In the mean time, you are experiencing a cylinder individual lambda control (CILC) adaptation It happens in exactly the scenario you are describing: low rpm / low load, steady pedal. The DME commands the wastegates fully open, and uses the precise exhaust pulse timing tables while adding / subtracting fuel one cylinder at a time, in order to keep the cyls balanced. You are seeing it happen, and I've seen the tables and code. However, many people still claim it does not exist, @Terry@BMS.

[NniftyFour]

OK so I have a question then. On Cobb AP V3 stg2 aggressive maps I would get zero percent WGDC off throttle. If I remember correctly the difference was between the intended catless vs non catless maps. The catless maps always had zero percent WGDC off throttle for me.

If no one else remembers this I might have to plug in my old laptop hardrive to make sure I'm not crazy. (It might of only been the first few minutes because I vividly remember the 0% as I would pull out of my driveway.)

[jyamona]

OK so I have a question then. On Cobb AP V3 stg2 aggressive maps I would get zero percent WGDC off throttle. If I remember correctly the difference was between the intended catless vs non catless maps. The catless maps always had zero percent WGDC off throttle for me.

If no one else remembers this I might have to plug in my old laptop hardrive to make sure I'm not crazy. (It might of only been the first few minutes because I vividly remember the 0% as I would pull out of my driveway.)

You may have seen WGDC Base read as 0. But WGDC Bank 1 / 2 should have been in the 12.X - 14.X range or so. Currently, even if you 0 out every WGDC table you will see this.

[Terry@BMS]

Claim what doesn't exist? Primary o2 sensor calibration based on rear o2 sensor feedback? Of course that exists. If you are talking about fuel trims per cylinder, I've never seen any evidence of it existing. If you have some post it up. Would be sweet to have the JB4 log AFR per cylinder if the data is in there and reasonably accurate.

[jyamona]

Claim what doesn't exist? Primary o2 sensor calibration based on rear o2 sensor feedback? Of course that exists. If you are talking about fuel trims per cylinder, I've never seen any evidence of it existing. If you have some post it up. Would be sweet to have the JB4 log AFR per cylinder if the data is in there and reasonably accurate.

Cylinder individual lambda control, as detailed in my post above. It is not the same thing as AFR per cylinder, and also different than STFT / LTFT which are per bank. This is simply an adaptation applied on top of the "flow data" that is stored in the DME when you code injectors.

Evidence of it in action is described by the OP, following the DME process exactly. INPA has a ton of params related to it you can log. I do it through custom RAM addr.

[idratherbesurfing]

Do you notice a loss of power when this happens?

[mastawyrm]

Do you notice a loss of power when this happens?

I've seen it do this plenty of times too. You only have to request like 50-60 load to make it quit immediately so no, it really is only noticeable in sound.

[bradsm87]

Currently you cannot manually set the WGDC to 0% in the tables, as there is an undefined table capping the lower limit. This table will be in the next XDF release though.

In the mean time, you are experiencing a cylinder individual lambda control (CILC) adaptation It happens in exactly the scenario you are describing: low rpm / low load, steady pedal. The DME commands the wastegates fully open, and uses the precise exhaust pulse timing tables while adding / subtracting fuel one cylinder at a time, in order to keep the cyls balanced. You are seeing it happen, and I've seen the tables and code. However, many people still claim it does not exist, @Terry@BMS.

That is awesome!

[GermanBoy]

are there now any solutions to prevent the wgdc to go 0% on cruise?

[ferocity02]

are there now any solutions to prevent the wgdc to go 0% on cruise?

According to jyamona, it's normal. It is a bit annoying though. I replaced my front lambda sensors and it still does it. It mostly happens while crusing on the highway, which isn't a big deal.

But very rarely it will happen in stop and go traffic, even while stopped and a light. This is the worst because there is a very significant drop in throttle response and the exhaust gets quite loud.

[Optigrab]

Cylinder individual lambda control

What purpose does Cylinder individual lambda control serve? Fuel economy?

[RSL]

No, voltage/flow of the injectors AFAIK. Coding sets the flow/voltage as a set point, but that measured starting point can and will change through use. Pretty sure that's the point of all adaptation tests.

The DME opens the wastegates to avoid exhaust swirling during injector adaptation tests, which are routine. There are conditions for the test to operate, just like any others though. Light throttle cruise is definitely one. Idle while driving (stopped at a light) seems unlikely, but possible. Like has been said a lot, it's normal and necessary to get proper readings.

[Optigrab]

No, voltage/flow of the injectors AFAIK. Coding sets the flow/voltage as a set point, but that measured starting point can and will change through use. Pretty sure that's the point of all adaptation tests.

The DME opens the wastegates to avoid exhaust swirling during injector adaptation tests, which are routine. There are conditions for the test to operate, just like any others though. Light throttle cruise is definitely one. Idle while driving (stopped at a light) seems unlikely, but possible. Like has been said a lot, it's normal and necessary to get proper readings.

Interesting....If the car does auto adaptations why does the injector flow data have to be programed in the ECU?

[RSL]

It needs a starting point for each and there are limits to how much it will adapt. The injectors use crystals, which won't all have the same properties from one to the next. They are each measured and tested when built, that's where the stamped numbers on then come from. As they are used, they will wear and change, just like anything else. AFAIK, the adaptations monitor injectors compared to AFR (needs to open the WG for) and makes adjustments (adaptations) to the injectors as needed.