Boost control: Open loop -> closed - why? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 08-16-2013, 08:10 AM   #1
Elite Member
Thread Starter
 
Chiburbian's Avatar
 
Join Date: Feb 2008
Location: Gilberts, IL
Posts: 2,158
Total Cats: 131
Default Boost control: Open loop -> closed - why?

I have read a bunch about boost control on the megasquirt and most of the time it tells you to tune open loop first before moving to closed loop. Aside from knowing what duty cycles result in what boost and thus knowing that your EBC is set up correctly, what is the importance? It seems to be mostly irrelevant once you verify the EBC polarity.

I am running closed loop now without ever doing open loop. I am thinking of going back to at least get something reasonable loaded into my MSQ, but I am having a hard time justifying why when my closed loop seems to be working.
Chiburbian is offline   Reply With Quote
Old 08-16-2013, 08:12 AM   #2
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,846
Total Cats: 1,787
Default

what are you reading?
Braineack is offline   Reply With Quote
Old 08-16-2013, 08:23 AM   #3
Elite Member
Thread Starter
 
Chiburbian's Avatar
 
Join Date: Feb 2008
Location: Gilberts, IL
Posts: 2,158
Total Cats: 131
Default

Boost Control
Quote:
Closed-loop Tuning Tips This section reviews some tips for tuning closed-loop boost control. Tuning closed-loop boost control should be done in two steps:
  1. Tune open-loop boost control - In order to make sure that you have the proper polarity set for your valve, and to get a feel for the boost that certain duty cycles yield, it is recommended that open loop boost control is tuned first.
  2. Set Up Overboost Protection - The closed-loop boost control code uses the maximum boost set in Overboost Protection for some of its internal calculations. This was done purposely so that during the tuning process for boost control, if the settings wildly incorrect, boost will still not climb any higher than the Overboost Protection allows it.
  3. Tune Proportional-Integral-Derivative (PID) gains - The PID gains are the main controls for how quickly the boost will reach the target, and how close it will remain to the target through the RPM range. Steps for tuning this can be found below.
https://www.miataturbo.net/megasquir...details-60323/

Those to start - for example.

Maybe it's just what most people have done to find success, but I don't think you necessarily have to do open loop.
Chiburbian is offline   Reply With Quote
Old 08-16-2013, 10:14 AM   #4
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,846
Total Cats: 1,787
Default

has ms3, reads ms1 crap.
Braineack is offline   Reply With Quote
Old 08-16-2013, 10:44 AM   #5
y8s
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 406
Default

tuning open loop when you have MS3 closed loop is like jerking off when you have a horny supermodel laying next to you naked.
y8s is offline   Reply With Quote
Old 08-16-2013, 11:33 AM   #6
Elite Member
iTrader: (3)
 
Join Date: Mar 2008
Location: Granbury, TX
Posts: 6,009
Total Cats: 583
Default

Agree. Would not bother at all with MS3. It has a full PID algorithm that works.

With MS1, the control algorithm is integral-only. Over much of the map, you HAVE to run open loop, otherwise you get integral-windup that causes big boost excursions. That's why the thread title specifically states MS1.
hornetball is offline   Reply With Quote
Old 08-16-2013, 11:58 AM   #7
Elite Member
iTrader: (2)
 
Join Date: Aug 2012
Location: Indianapolis
Posts: 3,325
Total Cats: 235
Default

MS3 dox for you.

Though you said it's already working, for everyone else that finds this thread this is what you should be reading.
thenuge26 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
LucaCarMods's Boosted Dutch Miata Build! LucaCarMods Build Threads 11 02-14-2016 07:13 AM
Going back to stock. Need some 1.6 parts. Trent WTB 2 10-01-2015 01:15 PM
Time to start learning and play with tuning The Gleas MEGAsquirt 3 10-01-2015 10:30 AM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 07:51 PM.