Boost control questions

[hardline]

Not sure if it is just me, but I have now worked on two separate vehicles running MS3 pre1.4 codes that boost control just plain old doesnt work. it just hunts back and forth between the extremes of the limits set in the boost control window with nothing inbetween. One of the vehicles is my own, and the other is a friend's which I flew out to retune. I rolled his back to MS3 1.3.4, and viola, it magically began to work the way it was intended. it seeks boost targets and varies the duty cycle accordingly to hold that pressure. What could I be missing, or is it a problem with the coding. No settings changes were made from the reflash from MS3 Pre1.4 Beta 10 to MS3 1.3.4, which makes me believe it may lie in the coding itself.

[muythaibxr]

msq? log?

[hardline]

Attached the tune files. The datalogs are too big to attach. I can email them to whomever needs them.

[muythaibxr]

You can cut down the logs easily enough to just show the problem.

[hardline]

I'll attach trimmed logs when I get home, probably about 6 PM MST

[hardline]

Sorry, just getting back to this. All hell broke loose at work and I just haven't had time till now to revisit this.

[hardline]

Anyone have any ideas? Only thing I noticed is that the control interval is adjustable on 1.3 and it is not (completely missing) on 1.4

[muythaibxr]

I will look today

[muythaibxr]

OK, what you're seeing is expected given what changed in 1.4 compared to 1.3.

Just a short set of notes about the changes:

1) In 1.3.4, the initial values table could be turned off and you could avoid using the lower limit delta as well by just setting it to a large number. This is no longer the case in 1.4. In 1.4 the type of PID loop was changed, which *requires* you to go into setup mode and configure the bias table appropriately. This means setting up the rpms on the x axis, the expected targets on the y axis, and the duty required to reach your target (or close to it) on the Z-axis. You should also set the lower-limit delta to ~20-30 kPa. This means PID won't engage until you're 20-30 kPa from the target, and you'll get a faster, more controllable spool. Once you get the "open loop" stuff working correctly, you can switch from setup to basic mode, and try to tune using the slider. IF you can't get it to act right after that, we can look at the specific problem you're having, and potentially work on going to advanced mode and tuning the individual PID gains.
2) People tended to set the control interval wrong for their setups in 1.3.x and earlier. You were a good example of this. You had a control interval of 10 ms but a valve frequency of 19.5 Hz. This means that your control loop was making ~5 changes for every possible actual change in the valve position. The fastest you can actually make a change to the valve position with a frequency of 19.5 Hz is every 51.3 ms. Setting the loop any faster than this doesn't make sense. In 1.4 we removed that setting since it caused a lot of tuning issues, and fixed the control interval to be correct for the valve frequency.

These changes result in a better ability to control boost, especially on systems that spool really fast, but require a bit more tuning to set up.

Ken

[hardline]

Is there any documentation on that setup process? I could not find it when I went looking.

[muythaibxr]

It is a new feature in a beta firmware. No docs yet aside from what I said in the above post.

[nathaninwa]

Here is the thread that got this started. The only big change is now there is a setup mode that keeps the valve 100% till your delta then you tune from there. It takes a little longer as you need to tune each boost value your wanting, I started at 200kpa and worked in 20kpa increments. Once the initial values are setup the pid seems to fall right into place. I like the new tuning method as it allows me to target peak tq at 5600rpm then add boost in to flatline tq, and the values needed are already there

http://www.msextra.com/forums/viewtopic ... 34&t=53051

[hardline]

OK. Still in the repair process on my car after tearing apart sintered iron connecting rods. Hopefully 1.4 will be at least release candidate by the time I have the replacement engine built and dropped in. Should be early April. Waiting on Winter to end.... d*** Colorado weather, it's in the 70s when I have to work, and it snows when I am off...