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For the past year I have been running my car with open loop boost control and have been dealing with different boost pressures based on ambient temps etc. Essentially in the mornings when its colder it will go higher than I'd like and lower in the afternoons. I mainly dealt with this as I was getting the car dialed in and any other issues worked out. This morning I decided to try and get CLBC working and have been having some issues with surging boost pressures. I did read the setup post but maybe I am missing something. My PID right now is 200.150.50 If I stay partial throttle it works pretty good and maintains around 6 psi steadily, but if I punch it then it overshoots hard and kicks overboost protection on. If I roll the throttle in lets say 4th gear after maintaining 6 psi slowly to WOT then it will boost up to 16, then creep back to around 11/12 but surge up and down. Im currently running MS3PNP for a 1.6 Here are the logs from this morning and my current tune.
My firmware is 1.5.1 and I also did not copy over open loop tables, I must have missed that step. My laptop died yesterday while trying to respond to the post so I wasn't able to try that. Here is a shot of my settings and tables. In open loop I am hitting around 12-14 psi fairly steady but it varies a lot based on outside conditions. I really would like to get it stable and more predictable.
It doesn't look like you did the stuff in the setup post yet. Start there and then we can help with the fine details.
Set your solenoid frequency to 39Hz
You are not ready to tune the PID yet. Start with "Basic Mode" after you have populated the bias table, adjust the slider until it is stable. Then you can go after response with the PID in advanced.
It’s been a while since I’ve read the setup post, but as far as I know the bias table should look like your open loop table. But that’ll all go out the window if you change your freq.
You're never going to get anything other than instant over boost with a Bias table that is 100% flat everywhere.
To word it better this is a base duty cycle, it's a starting point the the PID to work from. These should be the values that give you your desired boost level with no PID interaction
This should be a reasonable starting point for you
You're never going to get anything other than instant over boost with a Bias table that is 100% flat everywhere.
To word it better this is a base duty cycle, it's a starting point the the PID to work from. These should be the values that give you your desired boost level with no PID interaction
This should be a reasonable starting point for you
I totally forgot to do output I/O test and figure out my min/max PW. I did that today before driving home and my min is 25, max 48-50. I'm gonna punch in the numbers you suggest and go from there. I did notice it was a lot more stable after going to basic mode with the min/max correct and copying my OL table over.
I appreciate everyone's feedback. I will post some logs tonight with the updated values
On a side note: In MLV I can't find Boost Duty. It lists Duty 2 or 3 but nothing specific for Boost duty. Are the other Duty names just generic but are actually the Boost Duty I am looking for? Or is there something not being logged even though I am certain I have all logging values selected in TS
Last edited by L337TurboZ; 09-26-2019 at 10:03 AM.
What solenoid are you using? Seems like a very narrow BD range. Perhaps due to frequency? Perhaps due to valve selection. Perhaps due to Turbo / WG / WGA combination?
What solenoid are you using? Seems like a very narrow BD range. Perhaps due to frequency? Perhaps due to valve selection. Perhaps due to Turbo / WG / WGA combination?
I'm using the generic 3 port mac valve that's black/blue like what Cobb and everyone else sells. I have the valve setup as interrupt mode
Last edited by L337TurboZ; 09-24-2019 at 12:51 PM.
I have characterized several valves, at 79Hz, none of them have more than 40% or so of usable range.
I went and changed my frequency settings from 79 to 39 and rechecked its min/max. Min is now 15, max 70. Had it in setup mode and made a drive home. Boost was more stable and I did not have any surging. I'm going to set it to basic mode in the morning and do some logs. I'll post my results tomorrow.
I totally forgot to do CAN I/O test and figure out my min/max PW. I did that today before driving home and my min is 25, max 48-50. I'm gonna punch in the numbers you suggest and go from there. I did notice it was a lot more stable after going to basic mode with the min/max correct and copying my OL table over.
I appreciate everyone's feedback. I will post some logs tonight with the updated values
On a side note: In MLV I can't find Boost Duty. It lists Duty 2 or 3 but nothing specific for Boost duty. Are the other Duty names just generic but are actually the Boost Duty I am looking for? Or is there something not being logged even though I am certain I have all logging values selected in TS
Please explain the procedure for using CAN I/O test to determine min/max PW.
Please explain the procedure for using CAN I/O test to determine min/max PW.
I used the input/output test function to command the EBC to pulse. I set it to 39hz and went from 0 up till it began to click and then backed off 1 or 2. Then I went to 100 and decreased numbers till it began to pulse again. That's how I got my min/max numbers. It wasn't CAN I/O but output test mode I/O. I rephrased my original post so my bad for the name confusion.
That is quite the sensible procedure. To the basics. Thanks.
EDIT: @Ted75zcar , is there a basic reason to prefer 39Hz over 19Hz? For instance, is there a trade-off between range and linearity? Is there a wear issue in the solenoid, etc?
Data points we have:
79 Hz gives Min-Max 25-50
39 Hz gives Min-Max 15-70
19 Hz gives Min-Max 8-100
DNM
Last edited by DNMakinson; 09-26-2019 at 11:37 AM.
That is quite the sensible procedure. To the basics. Thanks.
EDIT: @Ted75zcar , is there a basic reason to prefer 39Hz over 19Hz? For instance, is there a trade-off between range and linearity? Is there a wear issue in the solenoid, etc?
Data points we have:
79 Hz gives Min-Max 25-50
39 Hz gives Min-Max 15-70
19 Hz gives Min-Max 8-100
DNM
I posted quite a bit of detail on this topic in my build thread, but the short answer is that the solenoid has a significant amount of dead-time in both the turn-on and turn-off portions of the cycle. At higher frequencies the dead-time consumes more of the available cycle period. The MS3 hardware that is typically used these days incorporates a flyback diode, so most of the turn-off time impact is minimized, but turn-on is always there. So the turn-on consumes the lower end of the available range, typically the first 30% or so. The turn-off prevents use of the high end of the control range, typically above about 80% DC.
The method described to determine min/max is effective to first order, and should in most cases minimize integrator wind-up to a tolerable level. The actual available duty-cycle (especially on the min side of things) is going to be higher. The solenoid will "click" before it actually opens, and then again, the non-linear effects during turn-on make the first few percent of the opening cycle kinda unusable (similar to small signal pulse widths with injectors). This is where you see people using the described method to get 15% instead of closer to 30%. My experiments monitored both flow (via pressurization of a known volume) and valve position using a linear position sensor.
It would seem practical now to select a lower frequency to optimize the control parameter dynamic range and resolution, but we have a secondary consideration. Typical wastegates/solenoid combos have a mechanical bandwidth of something right around 20Hz. This means that the wastegate valve itself can respond to the turn-on and turn-off transitions at lower frequencies. This is observed (and heard) by the valve ~vibrating~ at duty-cycles in the middle of the scale. Precision measurement of both the exhust pressure and the intake pressure actually show that this vibration results in pressure pulses in the combustion air. I have elected to move as far beyond the mechanical response of the valves as possible while retaining the widest reliable duty-cycle as possible, thus 39Hz (with the available frequencies on the MS3). I do have a home-brew controller that actually dynamically adjusts the solenoid frequency at the high and low end of the duty-cycle, effectivly extending the control range to 10-90%, but the added complexity ended up not being worth it for my application.
Interestingly, I fabbed several different baffles that would filter out the pressure pulses to the can and allow a lower frequency/higher control range and resolution.
Thanks. My 8% was based on when I actually got more boost than waste gate only. So that number is real. I look forward to trying the 39 to determine if I get better / more control at the top end. The older DIY would operate over a greater range of actual boost with a lower range of PWM, even at 19 Hz. The MAC valve seems to need the different frequency. (I am ignoring the mechanical part of potential issues with pulsations).
09-22-2019, 09:33 AM
CLBC Issues/Initial Setup
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