MS EBC Duty Cycle question
 

I set up my EBC last night. I have heard "you don't want to make it so that MegaSquirt has to intervene in order for your wastegate to open" which makes perfect sense. If something goes wrong with that signal wire and your wastegate never opens...boom.

I hooked up my EBC (DIY Auto Tune one) according to the directions on DIY Auto Tune, put in slightly bigger brass barbs to match the WGA barb, and then tested by blowing into one end of the EBC. with no power hooked to the EBC, air flowed through correctly from one barb to the other, and the 3rd hole (with no barb) was blocked.

But the term "duty cycle" confuses me a bit. When I hooked everything up and opened up Tuner Studio my duty cycles were all set to 100--and yet, the WGA was working as if no solinoid was in the way.

Did something get switched, and my MS is now having to intervene 100% of the time in order make my WGA work as stock? Or is that just the phrasing, and with, say, 90% duty cycle the EBC is getting a ground 10% of the time?

I noticed it said my polarity was "inverted" which I assumed was because I go from 12v+ to solinoid to MS ground (Normal polarity would be MS providing 12v+?)

Basically, I just want to make sure that if one, or both, of those signal wires to the EBC gets sliced somehow that my EBC is still going to be OPEN (wg pressure) and not closed (engineboom pressure).

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Am I correct about "normal" polarity being 12v+ from MS to solinoid to fixed ground? If so, wouldn't it make more sense to set it up that way?

Seems like as-is, if my wire running through my firewall from EBC to MS accidentally shorts and grounds out, I'll be having a bad day.

Sorry.. got very wordy but I think you get what I mean.

Also, flamesuit on, but I've been searching and even dug through msextra/megamanual.

Is this a MS1 or MS2? Can you post a copy of your MSQ?

MS2E from Reverant.

I'll post up my MSQ when I'm done with work, but I'm running open loop, polarity is inverted, and my duy cycle table is all 70% right now (100% was wastegate pressure).

I haven't changed anything EBC related from the "base tune" that came with the MS2E except to lower my duty cycle table from 100% to 70% which has me hitting 10PSI pretty quickly and holding 10PSI to redline on a 6psi WGA.

great advice: learn.

Seriously?

I have the EBC set up and working correctly. I want to make sure that if something goes catastrophically wrong with wiring it wont go catastrophically wrong with my engine.

I checked the stickies, found this https://www.miataturbo.net/megasquir...pnp-ebc-62711/ Yeah, it's for MS1 but it seems to be applicable, but he says he just used the defaults.

I followed the directions from DIY auto tune and from reverant and stated above that I have followed them and left the defaults.

I checked the mega manual and MSExtra and even posted above the content from that manual which applies--and doesn't answer my question.

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I'm not sure what else you're expecting of me here. I didn't find my answer in any of the above resources that I searched and checked, so I came here to a group of very knowledgeable people and asked a question.

If you'd rather, I can spend an hour in my garage with my multimeter tonight and try to figure out what all these settings do. But I personally felt that I had done a good amount of research before asking this question.

I think that is what the overboost protection is for....

Yes, they put overboost protection in your megasquirt so that you can ignore actually setting up the EBC correctly.


Brain, I'm especially surprised at your post above seeing as how it was YOUR post that got me thinking about all of this in the first place.


Post 32 here: Overboosting/boost creep - Page 2 - Miata Turbo Forum - Turbo Kitten is watching you test compression.

I've been confused by this as well. The manual here

Boost Control

Says that for open loop more duty is = less boost/more signal to the wastegate. IE 100% means the solenoid is totally open and giving the wastegate full signal and 0% means the solenoid is totally closed and the wastegate is getting no signal.

Polarity in the open loop boost control just reverses how those values get read by the MS it seems. IE if when you set it to Normal it acts as above and 100% is full signal to the wastegatae then flipping polarity to Inverted would make 100% no signal.

I'm still unclear on how the duty table relates to the closed loop boost control if at all.

What version of firmware are you on? The duty cycle has been reversed in 3.3 so more duty = more boost. If you ever plan on switching to closed loop control you have to make sure polarity is set correctly so that more duty is more boost. As long as you have overboost protection enabled and set to a sane value an EBC control failure will not be an issue.

Megasquirt MS2/Extra Loading firmware and Upgrade Notes

Closed loop control is now done differently.
Megasquirt MSEXTRA / MS3EFI • Boost control change testing (MS2 and MS3) (View topic)

No wonder this is so confusing.

To be clear, I will still get my overboost protection set up correctly, I just don't feel that a failsafe like that should make it so that I spend less time setting up the EBC properly in the first place.

Thanks for the replies. I'll post up my firmware version as well as my .msq as soon as I get a chance to get my laptop out of my car and grab the information--sometime this afternoon.

Here's my MSQ. Appears to be 3.30. Do I just need to switch from "inverted" to "normal" ?

If you're using open loop then switching from inverted to normal just changes what the values in the table equate to IE does 100 = no boost or does 100 = all boost.

I'm not even sure what that means for the closed loop tuning or if it means anything at all. I would assume nothing since it is disabled under closed loop. Seems like people just use it for reference to see whether the solenoid is reacting or not. The closed loop mode uses a different table with kPa targets and the PID settings.

Don't take my word for it though since I just started into tuning closed loop as well and I'm around the same place.

From MSextra on MS3 boost control:

So what they're saying is that higher duty cycles should let MORE air through.. but y'all are telling me that that's the opposite of true?

Forget everything the documentation says about EBC tuning. It's wrong for 3.3 an up firmware.

With 3.3 the duty cycle behavior is reversed, more duty means less air to the wastegate and more boost. Read over the first post of the msextra thread I linked, it explains how to setup closed loop control. Hint - you have to enable and setup the "Initial Values" table with all 3 PID values set to 0. Tuning Initial Values is like tuning open loop control. Once that's dialed in you can use the slider and PID values to fine tune control.

This is the future of MS EBC control. At some point in the beta releases they renamed it to Bias Table and made it required.

I don't understand how requiring the tuner to setup boost control with open loop then adjusting PID values is somehow easier than just adjusting PID values but whatever. Maybe it will make more sense once I start tuning it.

Thank goodness you posted this. I was going by the documentation and just got back in from trying to set up closed loop.. Was about ready to choke a bitch.

I and D both set to 0, the document says to tune P first starting at 100 slowly decreasing.

Well, with polarity "inverted" (the default, and what seemed to be correct per documentation) I couldn't get above wastegate pressure (about 4.5psi after pressure loss from fmic). Didn't matter what my P was set to.

With polarity set to Normal, I hit boost cut of 12psi no matter what anything else was set to. Dropped by target boost down to 7psi and tried a P of 95, tried a P of 30.. Didn't matter. I would over boost by 5psi,hit my boost cut, and nearly throw my tuning laptop out my window.

Sorry, beating a dead horse here, but this isn't true for me. At least not with the default settings.

Am I supposed to have the polarity set to "Normal"? Because it defaults to Inverted.

Unless I have it hooked up wrong. But per the instructions Dimitris sent me:
Which is how I have it hooked up.

As of right now I'm still running open loop because closed loop causes me to either be at WG pressure or infinitiy pressure depending on my settings, and with Open Loop, Polarity set to Inverted, Duty Cycle - 100 I'm at WG pressure. I dropped Duty Cycles to 70 across the board (basically using my ebc as an mbc kindasorta) and i hit about 9-10psi pretty consistantly on a 6psi wg.

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EDIT: and yes, I'm on 3.3. In a MS2E built by rev if that changes anything significantly.

if you're getting overboost and seeing no difference between P100 I0 D0 and P20 I0 D0 then you've hooked something up wrong.

P100 I0 D0 should be wastegate, regardless of your targets.

Ok. Then having my polarity "Inverted" is the way it needs to be. Which makes it so that open loop 100 duty cycle is WG pressure.

If I set it to "normal" I get hella overboost (man that gt2554 spools quick) even with p100 i0 d0 with target boost of like 7ishpsi (150 kpa i believe).

I'll try again on my lunch break. So, if I set my target kpa to 150 and p0i0d0 I should at least hit 7psi and possibly overboost a bit, and then fall back to 7psi, correct?

you also should be hooked up in a way that 0% duty cycle = wastegate and only anything about that adds boost.

otherwise this suggests the MS has to be running in order to run wastegate and if the solenoid/ms fails you will overboost.

when the solenoid is depowered you should be able to bloe directly through it to the wastegate actuator. in turn, this will open the wastegate. So if the solenoid fails, which they do, it will default to wastegate pressure.

when the MS rapidly toggles ground, only then should you raise boost.

p0i0d0 should overboost intensely.

Duuuudeee.

dont ever assume I read.


can you even in OL mode, set your DC to say 50% and hear it cycling?

I have not personally put my ear on the solinoid, but based on the above information I assume it is cycling correctly.

Ok, so I switched back to open loop and then switched my polarity to "normal" and now 0 duty cycle is WG pressure. 35% duty cycle had me holding about 9psi after spool.

I read through the prior linked thread on the new CL PID EBC tuning and i'll give it a shot this evening after work.

So when you say switch polarity, are you swapping the +12V and ground wires or is there a simple setting to reverse?

EBC noob I is. Just got my DIYAutoTune unit too and will be setting it up soon. 'Scribin for your eventual success to mirror.

I mean the "polarity" setting under the boost control settings in tunerstudio/megasquirt.

I _believe_ all it actually does is change the way that MS reads the numbers.

For example, when my polarity was "inverted" and my duty cycle was 100 I was at WG pressure. When my polarity was "normal" and my duty cycle was 0 I was at WG pressure.

Looks like you are on the right track mlev. I switched to open loop because I couldn't get closed loop working to my satisfaction and I wanted a fall-back solution until I got it right.

OK sweet that's a simple enough fix. I'm really excited for the spooling goodness of the EBC but it sounds like everyone has teething issues setting it up just right, open loop delivers variable pressures, and closed loop transitions are tricky. I've read hornetball's threads but still.

My MS1 will undoubtedly make it even easier lol.

This is fucking stupid and i'm about ready to switch back to open loop.

In open loop 100% duty cycle is now infinity pressure (closed solinoid) and 0% duty cycle is now WG pressure (4-5psi on a 6psi WG after pressure loss). 35% duty cycle holds me pretty steady at about 9psi.

CLOSED LOOP: I have my polarity set to Normal, with P100,I0,D0. To the best of my knowledge that should be WG pressure, right? Wrong.

https://www.miataturbo.net/attachmen...ine=1399590098

I spool up to about 11 1/2 PSI before lifting. 180ish kpa. My target boost is 150kpa across the board btw.

In my log file it looks like my boost duty cycle goes from 0 to 100 right around 112 kpa.

What am I missing here?

https://www.miataturbo.net/attachmen...ine=1399590098

Do I need to flip-flop my closed duty % and open duty %? Would be stellar if there was some documentation on this.

I'm glad you're doing this closed loop stuff. I was just about to do it and only barely figured out how my wastegate was acting up when I went over certain boost levels, between that and the whole 0 = 100, 100 = 0 thing I spent two weeks doing open loop.

Based on what you are seeing it seems like you need to go with the instructions they have here where PID starts off at 0 across the board? Or is the firmware not new enough?

Megasquirt MSEXTRA / MS3EFI • Boost control change testing (MS2 and MS3) (View topic)

Where is this "initial value" table they keep talking about?

Initial values table must have been added after your firmware version.

https://www.miataturbo.net/attachmen...ine=1399603434


I still say you should be set to normal polarity. What happens if you set P to 0?

Show us your boost target and initial value tables...

I'll try updating my firmware this weekend, but I'm on 3.3.0 so idkwtf.

it's an MS3 thing. I forget people still even run ms2. (ms2 got the initial duties thing in one of the 3.3.2 betas)


You should be using the 35% freq. value for the DIY solenoid.

and try starting at P 200.


also...do you have overboost protection on? another ms3 thing, CL won't work without overboost turned on.

Boost target is 180kpa everywhere. Initial value is pretty much a guess based on a couple pulls with open loop enabled and 100% untested. I expect lots of tweaking will be needed. But I just noticed timing is stuck in fixed mode so that needs to be worked out first.

Thanks Brain, I'll give it a shot. I didn't even realize I could do 200%...?

I have a feeling I'll end up building an ms3x here pretty soon...

That's the other thing I was thinking last night, you might have to go to 200% for P. Makes little sense when they list it as a percent value.

Is it just because the 2554 spools so fast? it seems odd to me that when I look at my log it shows the duty cycle going to 100 right around the time I hit boost, and then not even attempting to drop off as boost climbs.

Post your datalog

Few Questions
 

I've read this through several times and I've a few questions I can't answer from the thread:

Why would MS or the EBC completely stopping working risk over boost? Doesn't it then just go back to mechanical wastgate?
I can understand the danger if the electronics aren't working correctly but that would be a problem whichever way things are set up wouldn't it ?

Having it set in closed loop, is that better? Does it allow you to say ok my max KPa is 190 and whatever boost that reaches it then holds it there?

I've been running open loop for a year now and with the 100% in my boost table it's running wastgate only. It's taken a while to work out the table slowly dropping the numbers but it's getting there. Biggest challenge I found was how each gear gives a diff PSI and therefore KPa at the same revs. I was aiming for 12psi in 2nd max 185 KPa on a WOT pull and it took a while to realise that those figures just hit over boost pretty quick in 3rd gear.
Seems there's a percentage climb from gear to gear to me.

Then you need to tune your P value. Read the thread.

Scott, when you say "depowered" do you mean the ign key is in the off position?
I wrote down notes saying you need to plum your waste gate to Normally Open (NO) and Common. Further saying if you can't blow through it, it's wrong. Thanks, I just needed some clarification on this basic step.

By the way, can closed loop bring boost on slowly or change it with throttle position like open loop can? Open loop is super super nice for getting the throttle pedal and torque output to feel just right.

Dann

it's tps/rpm based and then ms3x has gearing/vss options.

if you wanted you turbo to spool up like a centrifugal supercharger you could make that happen. Or like smart people do, you can limit the boost at part throttle.

I've had solenoids fail. two of them actually. The first was the GM solenoid that is notorious for failing. The second lasted YEARRRRRRRRRRRs but I bolted it into a position that sat way too close to the turbo and it failed; I moved the replacement behind my intake cold air box instead of outside it.

Now, let's assume I had the EBC plumbed in a way that it was normally closed.

That would mean that you'd need to ground the solenoid in order for it to open up and run wastegate (this should make sense to anyone that has the most basic understanding of wastegate plumb).

So what happens when the solenoid fails, and the MS can't open it because it's fried? You'll always be running full boost in this scenario.

Sure, you'll have overboost protection on, but that sucks. It's just not a safe way of doing things. Plumb it correctly, and if it fails then you'll fail to wategate and you can safely determine something is wrong.

It just doesn't seem smart to me to power an electronic device up and run it backwards. Cruising around it should typically be off, it's not until you need it will the MS fully clamp to ground to spool the turbo, then rapidly cycle the valve to maintain the boost target. Not rapidly cycling it to maintain 0 boost in cruise...seems silly.

yes.


yes, gearing and weather changes OL significantly. If you tune in 2nd, you'll overboost in 4th. Or if it's a cold morning and you tune, you won't be anywhere close to your desired boost level in the afternoon when it warms up.

CL for layman's:

You: Hey MS, I want to run 15psi.

MS: okay; here you go.

That suggests it's trying to work, but something's not working correctly for the PID algorithm. That's why I suggested MORE P.

The most basically understanding of PID will help you wrap your head around it.

But if I suggest that P0 would overboost to infinity and P200 would only run wastegate, that should give you a clue. If P-100-200 doesn't bring you to wastegate then you have a plumbing or setting issue.

P is the rate at which the code will reach the target. It's the first part of tuning PID.

Once you get it close, you tune I, which maintains the target over time.

Assume you have tuned P to hit 15psi--that will ONLY be during spool--like 3000-4000RPM, at 6000RPM it will drop down back to wastegate since you have no I.

Setting P should take 10-20 pulls quick pulls in 3rd to spool the turbo up and get it close, so you'd be hitting like 16-17psi.

Once you add I, you'll do full pulls to redline to hold the target over time. This will effect P and you might have to add some back in to acheive the target with added I.

This is a dance, and you will have to go back and forth adding a few to each.

Finally you'll add D; which is basically damping. It will help remove any oscillation, but it will effect both P and I and you'll have to maybe lower P again to speed the spool back up again and have P just peak past your target again.

Once tuned, you should spool quickly, breaching your target by 1-2psi, hold it to redline, smoothly/solid.

If you ever need to change your boost target, or what to hit certain levels at certain TPS values or gears or vehicle speed--you only have to input those parameters--you'll never have to tune PID again.

Yeah same as open loop is, I want it to both limit boost at part throttle and spool up like a rotrex to keep torque on the safe limit from as low as possible to redline.

Dann

yes. but OL is dumb as shit and is only useful as an initial duty table for PID to reference.


but basically you're saying you want a slow shitty car? just run wastegate.

or, just remove the turbo.

Now after this thread Ill go sort the CL.

No this setup has a stock bottom end, so ramp it onto 230wtq as fast as it can and hold it there until redline by adding boost only as fast as it can while holding 230wtq. If it holds it to redline it would make 300whp and be within the 'known limits' of stock rods.

However It will end up limited to 250 odd rwhp.

The other thing I wanted to make sure of is controlling torque in a really flat manner at all throttle positions.

Dann

rods break by tq, the force pushing them down. not hp, a math equation.

but yes you can make it do that if you want. I would add boost after 5K so the torque stayed flatter towards redline.

Ill just add boost till it hits the target torque then keeps adding it enough to keep it there.

Dann

pretty much what i did within reason. added rpms + cylinder pressure + tq = bent rods as well.

I'm going to CL as soon as I have the chance to get out and do a few pulls to tune PID, OL is for the birds, bleah.

Hell, I just checked my TS that is linked with my actual car's firmware and I've got this whole initial values thing, so I guess this article I've been reading about the boost control doesn't apply at all.

Boost Control

And this is the actual thing I should be reading instead.

Megasquirt MSEXTRA / MS3EFI • Boost control change testing (MS2 and MS3) (View topic)

Also, why did I tune Open Loop if the initial values table thing basically does the same damned thing? Well, I guess I can pretty much just transpose the open loop values into the initial values table.

I honestly felt like I knew what I was going to be doing with the old setup after Brain explained it, now I have to think through the thing again as the above article seems low on detail to me.

Edit: Now that I read through the thread everyone thinks the new method is way better than the old one and easier to manage, so there is that.

tuning the OL table is a great step forward if you're going to be using the reference table; not a waste at all.

Well, my CL seems to be working better now. I changed the "Closed Duty Cycle" to 100 (because that's the duty cycle when it's closed) and the "Open duty cycle" to 0 (because that's the duty cycle when it's open). They were flip-flopped by default..

I also set my P to 200.

Did a pull and I hit my boost target on the head and then held there (although it took me a bit to get there). So something worked. I dropped by P to 150 and did another pull, hit boost target again.

I'll tinker with the P a little more (lol) and see if its just massively high P values that 'fixed' it, or if switching the open and closed DC fixed it.

On to tuning the rest of the PID! woo!

i dont believe the code will work when you do the open/closed like that. unless they changed that as well. But it used to be that it would break if closed was less than open, but that was also when closed/open referenced the wastegate, not the solenoid, so that might have been updated as well.