closed loop boost control aka Boost kpa targets - Miata Turbo Forum - Boost cars, acquire cats.

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Old 07-26-2008, 10:42 PM   #1
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Default closed loop boost control aka Boost kpa targets

Has anyone had success with the Boost kpa target table 1?

Meaning got rid of the oscillation when controlling boost with that option instead of the duty targets table.

I hate the idea that my boost control is so temperature dependant.

or is it a processor speed limitation of the MSI?

Last edited by paul; 07-26-2008 at 10:58 PM.
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Old 07-27-2008, 02:55 AM   #2
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I also have the problem with temp, when it gets below 60 degrees I overboost bad, I would love the closed loop to work. I cant figure out the closed loop, like you said nomatter what I tried it would keep oscillating and just acting weird.
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Old 07-27-2008, 09:32 AM   #3
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Paul,
my experience is that it will over and under shoot target boost in a sine wave type pattern, no different than closed loop fueling. Must use the same algorithms. I recommend avoiding it.
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Old 07-27-2008, 11:17 AM   #4
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hmmm http://www.msextra.com/ucp.php?i=pm&mode=view&p=62556

edit for correct link. that link is to the post only. here is the thread. http://www.msextra.com/viewtopic.php...st=0&sk=t&sd=a
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Old 07-27-2008, 12:56 PM   #5
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Intresting. I would really like to get open loop to work.
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Old 07-28-2008, 09:24 AM   #6
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We've found open loop is much easier to tune - our red car isn't running closed loop either. The open loop is fairly practical but the closed loop code is really difficult to get working right.
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Old 07-28-2008, 10:41 AM   #7
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since we are talking about boost control anyway, is there a known procedure to find PWM rate, and the proportional/integral values for a given solenoid?
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Old 07-28-2008, 10:49 AM   #8
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The open loop EBC code is considered to be fairly stable code by the developers, though the closed loop code is considered experimental- They'll do more with the MS2 with the additional hardware resources they have I'm sure, however the MS1E closed loop EBC always has been experimental code and I've never bothered to try and dial it in to perfection, though I've always been very happy with the open loop EBC functionality. I get slight (1psi or so) boost increase on a cold day, but in my case at least, it doesn't hurt me any as I've laid out my tables with this in mind, and the cooler air is less detonation prone to boot. If it was 3-4 psi I'd be concerned, and different setups may vary. In my config I see about 1psi or so and it has never been an issue.
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Old 07-28-2008, 10:53 AM   #9
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Stupid noob question, What is the difference between open and closed loop?

From what I vaguely remember it was the difference between the MS using gego correction against the fuel table and not. But I have no idea what it means when in reference to EBC.

I have my DC table setup perfectly, but like some here on colder days it spikes. Using boost targets would be pretty slick.
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Old 07-28-2008, 10:57 AM   #10
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Open Loop means the boost duty cycle is static based on a table. The ECU is not trying to read what the current boost level is in real time and target a certain amount of boost.

Closed loop means that the ECU is not targeting a static duty cycle, but instead has a table programmed to allow it to target boost levels at different areas of the tables and dynamically attempt to adjust duty cycle of the EBC valve to attain the desired amount of boost on the fly. The 'loop' is closed as it's reading from the sensor, and using this data to determine how it controls the EBC valve, which is turn effects how much boost is made, which effects the reading at the sensor that it again reads, makes another adjustment if needed, etc, in a constant loop.
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Old 07-28-2008, 11:07 AM   #11
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Quote:
Originally Posted by Saml01 View Post
Stupid noob question, What is the difference between open and closed loop?

open means it simple reads your DC% map and controls the solenoid to your table exactly.

close loop means it reads your kPa targets table and your current conditions and tries to control the valve on the fly to achieve and maintain your target.
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Old 07-28-2008, 11:11 AM   #12
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Quote:
Originally Posted by Braineack View Post
close loop means it reads your kPa targets table and your current conditions and tries to control the valve on the fly to achieve and maintain your target.
and then overshoots to 18psi, then undershoots to 11 psi, then overshoots, then overshoots over and over again.
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Old 07-28-2008, 02:04 PM   #13
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Considering we have 20+ degree differential throughout the day this time of the year in NJ I get a bigger change in my max boost than just 1psi so I was hoping to find a way to make KPA targets work better.
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Old 07-28-2008, 02:14 PM   #14
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I wonder if the EGO ignition events per step was lessened to like 10 or less if it would have an effect.... pulling **** out of my *** here.
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Old 07-28-2008, 02:43 PM   #15
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The boost change from ambient temp differences is exactly what drove me to set up closed loop on the link. Worst case I was seeing over 3psi in change.
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Old 07-28-2008, 07:03 PM   #16
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Yeah In 5th gear on a 80 degree day, I hit my 14 psi. On a 60 degree day, I hit the boost cut at 16 psi in 4th..
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