Boost PID=200,0,0 - still hits boost limit
 

Here is my problem. I have been running in closed loop for the past several weeks but since my boost was not tailored to this car, I decided to tune my PID settings. The boost hadn't been steady to my satisfaction and I figured it was time to start fine tuning.

To start with, I switched over to open-loop and set the entire table to 100 and did a pull. I immediately hit boost limit. I then switched the polarity to inverse and tried again. Now I was essentially on wastegate.

I then set my P to 100, I to zero, and D to zero.

I did a pull. almost immediately I hit my boost limit of 175kpa. I upped my P to 150. Same thing. Finally to 200, and same result.

What could be causing me to immediately hit boost limit in closed loop so quickly?

However, when I originally had my PID set to 22,20,70 and normal polarity I was fine, if sub-par.

I am using a new style DIYautotune boost solenoid.

Any thoughts? I'd really like to start turning the boost up slowly and maybe doing some gear based boost stuff but until I get the closed loop stuff working perfectly I don't think it's the right time.

Thanks!

Change the polarity back to normal.

Be careful using settings from ebc tuning threads esp for ms2. Older msextra firmwares were written such that less duty = more boost. The latest versions have been changed so that more duty = more boost. If the polarity and/or open and closed duties are backwards it will overboost regardless of the pid settings.

Will do, but why don't they say that on the ms3 documentation site? It still says 0% duty means closed wastegate and more boost.


Boost Control

The manual has not been updated to reflect the latest firmwares.

Well that's helpful... Thanks. I'll give it a try in a few minutes.

The manual reflects release firmwares, it's only the Alpha's/Beta's currently which have the boost control flipped (to the correct way IMO).

The latest Alpha/Beta firmwares also have tooltips within TunerStudio so you shouldn't need to use the manual anyway.

did that fix it?

Yes, but I am not happy with how it is holding boost. I spent about an hour on it yesterday and I am not any happier with MY numbers than the numbers I started out with.

I am not hitting and staying at my targets. My target is 162kpa.

Attached are logs at different PID settings. The numbers are in the file name.

P19,I20,D71 is what I started with yesterday and what I returned to today.

P18,I36,D55 is what I ended with yesterday and I didn't see/feel enough of an improvement and I was unsure if I actually made an improvement.

what boost does your wastegate only give you?

can you post screen captures of these boost pulls?

I am away from my tuning laptop for a bit and I will post screenshots when I get back.

My wastegate brings me to about 155-160kpa.

you should just add preload to your wastegate actuator if you're only targeting like 1 psi over...

The idea is to start by getting 10psi as soon as possible and ride it to redline. From there, add a pound or so at a time while working on my tune. My eventual goal is about 220lb/ft torque and whatever HP comes with it. You think I would be better served upping my boost target to 175kpa or so while tuning?

By "eventual" I mean the max I am comfortable with until I build an engine.

Upped the 100% throttle line target from 162kpa to 170kpa. Raised the overboost to 180kpa.

This is the result:
https://www.miataturbo.net/attachmen...1&d=1376958512

Is the "sawtooth" motion normal cycling of the valve? Would I need to raise I and lower P in order to reach my targets?

i dont think you have enough p. i feel like most people end up around 25-30 or so for p.


you should be tuning by:

starting with like 100p only, the rest at zero.

reduce p until you breach your tuning during spool up.

start doing pulls to redline, increase i to hold target to redline.

increase p as you increase i to maintain the spool-up target.

increase d to reduce the sin-wave pattern.

increase p and i to keep hitting spool-up target and maintain target to redline.

increase d to reduce the sin-wave pattern.

increase p and i to keep hitting spool-up target and maintain target to redline.

eventually get close enough where when you spool you should end up with a 1psi spike over target and hold it to redline with very minimal oscillation.

Actually that's exactly what I did.

I think that by having my target so close to wastegate I might have been making it difficult to really see what is going on. I am going to start over and set boost limit to 185kpa with a 170 target.

Part of the headache is doing this all myself with a sub-par location to do test runs.

What gear are you tuning your P in by the way? How about the other two?

Should I be switching my closed and open duty percentages as well since I a running "Normal"?

Tried working on it during an hour long drive home on country roads. Unfortunately, I hit the + button instead of the = button. I wanted to set my target boost to 62kpa, instead I set it to a target of 330ish kpa with my over boost set to 173. No wonder it wasn't acting predictably. Back to the drawing boards tomorrow.

I just checked and I am pretty sure I am using a release version 1.2.3

My tunerstudio file says I am running MS3.

Here are my pages as they stand this morning:
https://www.miataturbo.net/attachmen...1&d=1377263362

https://www.miataturbo.net/attachmen...1&d=1377263362

What gear are you starting your "P" Pull. What RPM?

I feel like I am starting with something wrong in my setup which is really making it worse than it needs to be. Also, I don't have tooltips as far as I can tell.

In which case it's as per the manual, and more duty = less boost.

closed duty cant be greater than open duty.

you need to make closed = 0% and open = 100% and then use inverted polarity.

I was right about stuff being fubar. I checked my project properties and it indicated I was running MSZ3 .262 or something like that. I did a "check for ECU" or whatever that button was and it came back with a firmware of 1.2.1.

So I have been running a mismatch of sorts between what tunerstudio thought I was running and what I actually was. This might have something to do with many of my random minor problems.

Brain: If I was using alpha code where I would be running normal as opposed to inverted, would I still be keeping closed = 0% and open = 100%?

If I were to start over with Alpha code, my settings should be to start:
Output Polarity: Normal
Closed Duty: 0
Open Duty: 100

Start P at 100 etc...

Correct?

Am I better off just going to 1.2.3 and running inverted for now to minimize having to make other adjustments?

correct; at least that's my understanding.

According to Megasquirt MS3 Loading Firmware:

So it appears that the change was made before the current version I am using. It appears I should stick with normal.

I'm on 1.2.1 and mines still inverted IIRC and it works. maybe i changed it? I dunno.

I used 3rd gear to tune the p term initial overshoot, and repeated pulls to the redline in 2nd, 3rd, and 4th gears to tune integral and differential gains. Good luck, cl boost takes patience to tune well.

By initial overshoot what rpm are you referring to? In order to get any overshoot I had to lower my P to something like 7, and then it was at about 4,200rpm.

To be honest, I am a bit lazy about it right now. I am at something near my original numbers at 20:22:100 right now and it feels a lot better than it has been while trying to find P, and frankly I have been just messing with it while driving to see what seems to be better by watching boost gauge on dash. Looking at a quick log, I am back to a situation where I am not hitting/overshooting target until higher RPMs and then in an oscillating fashion. But it feels good and seems safe so I am not too concerned at the moment.

Sunday I am off of work and I will start doing some tuning while watching my logs and we will see how it progresses.

EDIT TO ADD:

Reading some more it looks like some of what I was doing was wrong, some of the time. I thought for some reason that tuning P had to be done in a low gear rom 2,000rpm up. That doesn't really result in a super rapid increase in pressure compared to say, starting at 4,000 rpm in second. I THINK I will end up about where I am at with a starting P of 7, but I will re-test a bit tonight and tomorrow.

Here is where I am at as of about 5am today.

https://www.miataturbo.net/attachmen...1&d=1377513121

I overshoot almost to 185kpa and then settle near target. I am thinking that means I should up D some?

Overall, pretty good.

Virtual Dyno tells me it is about 189hp and climbing. I didn't even go to redline.

https://www.miataturbo.net/attachmen...1&d=1377513349

Still some tuning to do obviously but pretty happy with it at this moment.

EDIT:
Superimposing my old pull on this one tells me that I am actually making LESS power. Mind you that was a 5th gear pull and this was a 4th gear pull but still. Surprised. Either way it feels pretty good.

What PIDs on this last one? Looks like to little P - add P of 1 or 2 and try again...

Also - I would set the Boost lower limit delta more to something like 40 or 50 because that keeps the valve shut for a
longer time - so boost can rise faster...

This is true for ms2, but the ms3 tuning procedure does not reflect the changes since in ms3 release 1.2.x

Reading the end of this page: Megasquirt MS3 Loading Firmware clears up some confusion over the correct output polarity for the OP's valve compared to the correct output polarity with ms2 release or older ms3 1.1.x codes.

Here is where I am at today. I started over and ended up pretty much where I was before.

Back on 8/26 I was at 8:5:60

Today I am at 10:5:0 (not tuning D until I get a few things worked out). Target is 172kpa.

I am not terribly upset with how I am holding boost to redline as you will see in the following graphs, but it does seem that I am getting some oscillation as I go up in RPMs. Also, in lower gear pulls I barely ever touch my targets. Heavy oscillation. I don't have any logs of that though.

https://www.miataturbo.net/attachmen...1&d=1378480030

What I AM seeing however is heavy overboost when I do a full throttle pull in higher gears. For example, the log/graph below is a pull in 6th gear.

https://www.miataturbo.net/attachmen...1&d=1378480030

What should be my next step? What should I try?