I’m getting closer to getting boost control switched from the Eboost2 to the MSPro but I have a question.

For the Overboost setting I have it set to 240kPA (34psi).
Test runs had the car shutting down at exactly 20psi of boost.

DIY informed me that the first 100Kpa is atmospheric pressure which then equals 20psi thus shutting things down. If I just change the overboost setting to 340kPA is this all I need to do?

Also, for the hysterisis I have it set to 40kPA and if I understand correctly this is how far the boost will drop IF the overboost is triggered. Is this an acceptable value? My thinking is that I don’t want the boost to fall too far below my desired boost level of around 32-33psi..

KS

 

You are correct, 0-99kpa is vacuum. 100 is atmos, 101-up is pressure (non-scientifically speaking).

My understanding: The hysteresis is for entering and exiting the loop. If you have cut at 340kpa, and hit it, then the system will need to drop down to 300kpa before boost cut is turned off. Then the system is ready to go again.

 

ok... It sounded that simple but.....

ks

 

100KPa = 14.5038Psi

100KPa is atosmpheric pressure at sea level only and varies slightly throughout the day/year constantly
You can goto google and type "KPA to PSI" To get a calculator for all your values

Hysteresis is like a range for for a decision that may be used to account for system memory.
https://www.sciencedirect.com/topics/engineering/hysteretic-control

For our applications it usually only functions as a control setting to prevent unwanted rapid switching of an output.
For example if fan-on temp is 180*F and hysteresis is 5* the fan could start at 175*F-185*F
Or if boost enrichment (Hptuners) is activated at 105KPa with 5KPa of hysteresis it might activate at 100KPa-110KPa.

Imagine the temperature was rapidly fluctuating around the set temp, 179.8, 180.2, 180.1, 179.4, 181.2, etc...
Because of noise or whatever.
You wouldn't want the fan to start and stop rapidly, it could wear out the driver, or motor, or something. Depends what is being controlled and how. So they give it a 'window' where the output remains on even though there is noise or sensor variation.

 

I've been using the conversion tables just didn't know that 100kPA was the "Starting point".

Do I want the hysteresis to be a "re-activation" point to turn boost back on, say 29psi?
I need to look at the log from last night but it didn't seem that boost kicked back on at 14-15psi (hysteresis set to 40), it just shut the car down.

ks

 

It should not stop 'controlling' boost unless there is an accident or problem


Electronic boost control is a form of PID Control.
https://en.wikipedia.org/wiki/PID_controller

The underlying proportional, integral, derivative (PID) theory is useful and repetitive, seen alot in electronics (worth the time to learn)

Boost controllers can run open loop or closed loop. Your computer can do either way.
It seems like you are struggling with the closed loop and safety features. I would maybe recommend trying an open loop boost control first to see how it works and responds. Then attempt the full closed loop feature. Just a thought.

As to your question.
The question you are asking doesn't make sense to me. "re-activation point" I am not sure what you mean. It should not turn off the controller while in boost at all. Hysteresis set to 40-> 40 what? 40psi? 40KPa? I am not sure what you ask.

If you want help with the table you are adjusting simply post a screen shot of it I will guide you.
To take screen shot press "Print screen" Then open paint and paste the picture, then you can crop and upload.

 

There is absolute pressure, and gage pressure. The setting you refer to here is Absolute. 100KPA absolute = 0psi of boost pressure at sea level. So when they say 240KPa it is exactly as you understand, 20psi of boost + 14.5psi atmospheric = 34psi total absolute pressure

If the goal was to raise the boost cut point from 20psi to 34psi total then yes

I would need to see the table to know how they are using the word hysteresis. 40KPa is like 5psi range, if associated to overboost setting then perhaps it will re-enable the boost once it falls back down 5psi below target maximum. However like I said before it should never trigger the cut point. You don't want boost fluctuating up and down at all. Your goal as a tuner is to achieve the smooth boost control as desired (a smooth line for boost signal is usually desirable but it depends of course on target torque). e.g. Any attempts to lessen or increase boost on the top end should be done using control and not a overboost function.

 

I am in Open Loop.

Understand that I have only made one run with the MS controlling boost and it completely fell on it's face at 20psi and never came back up to boost. My initial "perception" was that the hysteresis value of 40kpa (14-15psi) wasn't correct or some other setting was causing the engine to not get back up to boost. Just now I looked at the log in more detail and realize that I didn't stay WOT long enough for the boost to drop that low so this is why I never saw boost after the boost protection was activated.

Hysteresis for the MSPro is how far the pressure drops. So boost will fall 40kpa (5psi) before reactivating normal boost control.

Moving on:
Lets just stay in psi for the sake of discussion:
I understand the Overboost is to kick in when boost gets too crazy.
Desired boost I want is 32-33psi. With my Eboost2 the boost never varied more than 0.3psi so I set the MSPro Overboost Protection to 34psi.

Q: If the OB protection kicks in I think I want the normal boost control to kick back in around 29psi..? Or should it be closer to 31psi or far less like 18psi? What's the general idea?

Last night when the OB kicked in it shut the power down fast and hard like activating the brakes and I didn't expected it to be so harsh. I expected it more like a rev limiter - but now I know what to expect. Realistically if the power shuts down that fast/hard like it did last night I will completely let off the throttle and abort the run.

ks

 

You should never hit overboost protection. The setting is for when an emergency or problem occurs and you should abort the run completely. You could set hysteresis to 20psi or 30psi so the engine completely cuts out and doesn't try to keep running while something is damaged.

On the other hand, maybe you have to win races and accidentally trigger the overboost due to traction issue (load during a shift causes boost to spike) or whatever.
In that case you don't want to abort the run, just save the engine and keep going.

This is a personal preference. To me, overboost is only for shut-down abort the run. To some, they don't mind tagging the rev limiters and boost limiters from time to time. I would never 'tag' the limiter because its hard on parts, can cause its own slew of reliability issues, especially "tight" limiters which allow repeated "banging" off some high RPM or boost point.

End of the day you need to decide what you want, then tune for that outcome. If losing a race is going to cost more money than losing an engine for example, you might not use such a tight 'leash' on the overboost setting and let it just barely hold things in check. If the engine is valuable then be more careful with the control setting and try to avoid hitting the limiter completely.

 

That's exactly what I need to know. I will simply use it as a safety feature and if it gets activated I'll just abort the run..

thnx!
ks

 

Sure thing. This type of control system is highly variable so there is never any clear cut setting.

Between the ECU decision and the solenoid there is a driver. The driver has an input and output frequency and there is something called a frequency response. The response to a decision from the ECU is based on so many variables it is difficult to discuss briefly.
There is also the issue of moving fluids through tubes (air is a fluid). The small hoses connecting solenoid to gate for example- their length and diameter is part of the response to a decision from the ECU and must be treated separately, empirically (experimentally) to dial in some exact behavior.
Furthermore the solenoid operates with some frequency range and displays its own characteristic behavior based on driver frequency output.

At some frequency settings the response will be more sluggish and the solenoid may become noisy.
The choice of what frequency to drive devices is based on the device and how it will be used.
For example in a robotic jelly-fish at my school they set the frequency of driver to peak resonance which conserves energy/battery.
In another example, pumps like fuel pumps may operate more smoothly/quietly with specific frequency drivers

In your example everything adds up. The response from the ECU, the power and frequency of the driver, the length of hoses deliverying the signal to the gate, the current velocity and direction of fluids within those tubes at the time of decision,

there is usually magic setting range where everything will work perfectly and smooth/quiet
And there are all kinds of ways to mess that up. Too long of hoses for example delay a signal and cause overshoot, undershoot or wavering of the result. Wrong driver frequency cause rough/noisy solenoid operation.

I like open loop for boost control because closed loop will account for changes over time which may obfuscate (obscure or cover up) issues such as vacuum leaks which need to be taken care of immediately and not masked by closed loop.

 

I'm glad a have a good baseline with the Eboost2 with only 0.3psi of boost fluctuation so I now hope the MSPro is as steady.

The only reason I'm switching to the MSPro is b/c the EB2 will out of nowhere power down/up so I figured I might as well see if I can get the MS to control it.



ks

 

Cool man. Wish I had ecu control but I'm forced to use $35 OEM 411 ecu to keep torque management which is my fav ECU feature.
My fav boost controller is ancient, Greddy Profec B Spec-II

Inferior in many ways to modern ECU control. But it can do the one important thing: It can hold a gate shut completely until the boost rises above a set point- making it helpful for spooling on the street with a large cold turbine, low egt

Solenoids are 'drived' at some duty cycle % "DC" just like pulsewidth for injector solenoids
There is some max DC a solenoid can be effective range to work in which depends on their construction and the driver frequency and wave/signal modifiers such as proportional gain.

Most boost controllers have effective ranges 30% DC to 60% DC
22% to 30% and 60% to 72% are sort of 'maybe'
It is rare to drive a 3-port style effectively past 80% for boost control or less than 20% DC.

The duty cycle represents a fraction of the spring pressure, plus exhaust gas pressure. We take exhaust gas pressure and add spring pressure to find the total boost pressure for gate opening. The gate manufacturer provides gate valve diameter (effective diameter of wastegate valve) and this is used to find the total pressure applied to the spring (larger valve = more pressure applied to spring = easier to open the gate)

This way one can work backwards from boost pressure to find exhaust gas pressure, given some spring pressure. But more importantly what the boost can effectively raise

 

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8/7/22 -
Bringing this thread back up for some help/thoughts:

Initial test with the MSPro controlling boost instead of the Eboost2 proved decent but a tad low on boost (27psi instead of 32psi). Maximum MAP was set at 340kpa so I raised it to 365 and went for a blast but boost was lower at a max of 25psi.

Given the screen shot of the solenoid and other settings is there something I can change to get the solenoid to get more boost like Maximum Duty(%) or Solenoid Frequency, etc?


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In open loop the ECU isn't keeping track of boost pressure, so it will always wander based on ambient conditions and solenoid route. For example if the solenoid is fed from the pre-intercooler than as the compressor heating up the air will be less dense at the same pressure so your map sensor in the intake manifold will gradually report less and less boost pressure even though the solenoid commanded duty is kept the same.

Next, I would never allow 100% duty cycle to the solenoid as it could create a tremendous boost spike. Perhaps 75% is a safer value. Every solenoid is different and the frequency driver is also playing a role, it must be tested and often a test can mean a rapid boost spike unwanted so I do not recommend too much messing around with limits.

In general you will raise or lower the frequency/duty cycle of the solenoid switching and depending on how the solenoid is routed to the gate, there are many ways to connect a solenoid to the gate and many different types of solenoids, you will need to raise and lower freq/duty in small steps to determine what the minimum and maximum boost control is capable of. For example if you have a 15psi spring in the gate with 1:1 intake:exhaust pressure ratio and a 3-port solenoid connected in a traditional fashion with the boost pressure feeding the solenoid which is feeding the dome, a typical maximum duty will be around 70 to 80% and max boost pressure will be near double the spring or approx 28psi or so.

The max setting is just for boost protection, it doesnt influence the duty cycle during normal boost.
There should be another place where you adjust duty cycle directly, a graph with some axis such as MPH or RPM is used vs duty cycle to the solenoid to adjust boost control. The one you show is just setup to turn the feature on and off and set the boundary for operation.

 

My over simple understanding. Open loop you are commanding a target duty cycle. Normally off a table. Closed loop you are commanding a target boost pressure. Something should be a table.

 

Don't know anything about a boost table but I found it and the 40 on the log file apparently came from this table..

Since I prefer to command a boost pressure maybe I should use Closed Loop..? I'll do some reading..

Thanks Gents!
ks

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Looks like it was working just as designed! Switch to closed loop or add duty cycle to that table to increase boost.

 

Sounds good... I just need to understand how all these settings work but I may be closer to getting it to work than I think.

I will change the max boost back to 340kpa which should give me 32psi then start adjusting other parameters from there.

ks

 

sound like there are a few misunderstandings here. overboost protection is not a target it is a point that if you hit it it shuts the engine down, say if the solenoid sticks, or you blow out a line or gate or if you know at what point the rods will divorce the engine.

i would stick with open loop it is more reapeatable than closed loop in my experience. closed loop can be nice but it take alot of tuning of a pid loop.

also why not "use" your table instead of a static number. you can vary your boost by throttle and rpm with it.