Baro Correction Sensor Install Clarification - 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 11-16-2012, 05:23 PM   #1
Hear me Meow
Thread Starter
iTrader: (3)
 
skidude's Avatar
 
Join Date: Apr 2008
Location: Outside Portland Maine
Posts: 1,993
Total Cats: 13
Default Baro Correction Sensor Install Clarification

I bought a second MAP sensor to add to my MS3 so when I move to the mountains I'll be ready. Now I'm finding conflicting information on how exactly to install it.

Option one by Joe Perez:
Simply purchase a second 250kPa sensor ($28) and install it inside the case, upside-down and backwards across the pins of the first MAP sensor, with the signal pin bent up and wired to JS5.

Option two by richvrlimited and confirmed by Braineak:
Includes a couple extra components; this appears to be on MS1.

Obviously Joe's solution is easier, but will it work? Most of the info I find searching is about some 4bar sensor, or talks about how baro correction doesn't work well on MS1.
skidude is offline   Reply With Quote
Old 11-18-2012, 10:17 AM   #2
Hear me Meow
Thread Starter
iTrader: (3)
 
skidude's Avatar
 
Join Date: Apr 2008
Location: Outside Portland Maine
Posts: 1,993
Total Cats: 13
Default

Nobody knows, huh?
skidude is offline   Reply With Quote
Old 11-18-2012, 02:49 PM   #3
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

You're asking if the solution I posted will work? Of course it works. Why wouldn't it?


What you've read about the 4bar sensor is simply an artifact resulting from the release of the MapDaddy as an alternative to this kind of hack. The MapDaddy uses 4 bar sensors of a different design, primarily because two of them are small enough to fit upright into the space consumed by a single MPX4250.

You have to use the same type of sensor for both main MAP and baro, but aside from that, you can use any two of the same sensor you want, regardless of their scaling.
Joe Perez is offline   Reply With Quote
Old 11-18-2012, 03:35 PM   #4
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

ms3 can use different size map sensors. but you still need two caps and a resistor.




Attached Thumbnails
Baro Correction Sensor Install Clarification-conbaro.gif  
Braineack is offline   Reply With Quote
Old 11-18-2012, 04:41 PM   #5
Hear me Meow
Thread Starter
iTrader: (3)
 
skidude's Avatar
 
Join Date: Apr 2008
Location: Outside Portland Maine
Posts: 1,993
Total Cats: 13
Default

Quote:
Originally Posted by Braineack View Post
ms3 can use different size map sensors. but you still need two caps and a resistor.
Joe's solution still doesn't mention caps, but he's sure it will work, and Brain specifically says to use caps and a resistor. Unless I missread Joe's solution and he also wires that extra stuff in... I wonder if I have those components laying around. It's been a long time since I have opened my megasquirt, are the caps and resistor included in Joe's solution already because they're somewhere else on the board and I'm sharing them with the MAP sensor?
skidude is offline   Reply With Quote
Old 11-18-2012, 05:06 PM   #6
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

you need them else it wont work bro. Joe's solution is "our" solution, but he left out key ingredients for success.

and i disagree with what joe said about same same baro sensor to map.
Braineack is offline   Reply With Quote
Old 11-18-2012, 05:12 PM   #7
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Yeah, we're really talking about the same thing here.

The "sensors must be the same" applied to MS1 and 2. I hadn't noticed that you had an MS3.

The .1uf cap between +5 and GND can be omitted, since there's already one on the main sensor that you're bridging across. The other cap and resistor are a noise filter on the signal line, and that must be replicated on the second sensor.
Joe Perez is offline   Reply With Quote
Old 11-18-2012, 05:13 PM   #8
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Serious question, as it's been a while since I've read up on any of this:

Who cares about barometric correction in a MAP-based system? Seriously, what is it accomplishing?
Joe Perez is offline   Reply With Quote
Old 11-18-2012, 05:15 PM   #9
Hear me Meow
Thread Starter
iTrader: (3)
 
skidude's Avatar
 
Join Date: Apr 2008
Location: Outside Portland Maine
Posts: 1,993
Total Cats: 13
Default

Ok, thanks guys! That clears it all up for me.

Now that you mention it, I don't know why it's necessary either I just know I'll be driving up and down big mountains a lot in the future and they say it's a good thing to have.
skidude is offline   Reply With Quote
Old 11-19-2012, 11:12 AM   #10
Supporting Vendor
 
Matt Cramer's Avatar
 
Join Date: Sep 2006
Posts: 2,266
Total Cats: 51
Default

Quote:
Originally Posted by Joe Perez View Post
Serious question, as it's been a while since I've read up on any of this:

Who cares about barometric correction in a MAP-based system? Seriously, what is it accomplishing?
Mostly, compensating for different levels of exhaust back pressure.
Matt Cramer is offline   Reply With Quote
Old 11-19-2012, 11:59 AM   #11
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

the Baro corrections are in real time, so it'll always be referencing MAP to what the atomspheric pressure is. That can make a big change in the amount of fueling youll need during large elevation/pressure shifts.
Braineack is offline   Reply With Quote
Old 11-19-2012, 12:23 PM   #12
Senior Member
iTrader: (5)
 
Join Date: Sep 2009
Location: Lompoc, CA
Posts: 579
Total Cats: 12
Default

Quote:
Originally Posted by Joe Perez View Post
Serious question, as it's been a while since I've read up on any of this:

Who cares about barometric correction in a MAP-based system? Seriously, what is it accomplishing?
Going from the 5500 ft at my house up the fun mountain road to 10,500 ft. baro correction makes a big difference. However, I found that tuning out the barometric scaling table fixed all of my issues. I think the problem roots back to the issues with the physics equations being incorrect. So MS wants to pull way more fuel than it needs to with varying altitude. By adding back some fuel % based on initial baro readings I was able to fix these problems.
baron340 is offline   Reply With Quote
Old 11-19-2012, 12:27 PM   #13
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

While I haven't tuned it. I'm sure using the Baro Corrections Table in MS3 is pretty easy to tune: just add/subtract % of correction at a giving Baro reading to keep the fueling equal.

Just make sure to start with a tuned fuel map.
Braineack is offline   Reply With Quote
Old 11-19-2012, 12:27 PM   #14
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Quote:
Originally Posted by Braineack View Post
the Baro corrections are in real time, so it'll always be referencing MAP to what the atomspheric pressure is. That can make a big change in the amount of fueling youll need during large elevation/pressure shifts.
In a system where air entering the engine is measured by volume, I can see this. It's why the '90-'93 MiatŠ had a baro sensor inside the ECU.

But in a MAP-based system? A manifold pressure of 80 kPa is 80 kPa whether it's the result of the throttle being partially closed or the result of WOT slightly west of Denver. When we turbocharge our cars, we don't need to give the ECU a reference as to the ambient pressure inside the intake tract just before the throttle plate.


Quote:
Originally Posted by Matt Cramer View Post
Mostly, compensating for different levels of exhaust back pressure.
This I can maybe see. (Instinctively, I wouldn't have though exhaust backpressure to change radically with elevation. At least, not by a significant amount as compared to the normal magnitude of exhaust backpressure. Valid point, though.)
Joe Perez is offline   Reply With Quote
Old 11-19-2012, 12:35 PM   #15
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

Correct me if I'm wrong, but a MS running MAP alone, with a baro reading taking on startup, running on a perfect tune, then drives 5000ft. in elevation, will have leaned out AFRs until the car is reset and the thinned out air can be metered. Because that reading is part of the fuel equation.

Maybe if you turn off corrections completely you would be correct. I'm not well versed in this. But I do like that exhaust backpressure part of it. Even still, with an initial reading you'll still want to tune the non-linear table to fine tune the amount of corrections, as I'm pretty sure the default algorithum is not ideal.
Braineack is offline   Reply With Quote
Old 11-19-2012, 02:19 PM   #16
Senior Member
iTrader: (5)
 
Join Date: Sep 2009
Location: Lompoc, CA
Posts: 579
Total Cats: 12
Default

Quote:
Originally Posted by Braineack View Post
Correct me if I'm wrong, but a MS running MAP alone, with a baro reading taking on startup, running on a perfect tune, then drives 5000ft. in elevation, will have leaned out AFRs until the car is reset and the thinned out air can be metered. Because that reading is part of the fuel equation.
Maybe if you turn off corrections completely you would be correct. I'm not well versed in this. But I do like that exhaust backpressure part of it. Even still, with an initial reading you'll still want to tune the non-linear table to fine tune the amount of corrections, as I'm pretty sure the default algorithum is not ideal.
This is exactly what I found to be true.
baron340 is offline   Reply With Quote
Old 11-20-2012, 06:07 PM   #17
Supporting Vendor
iTrader: (1)
 
Join Date: May 2010
Location: San Diego
Posts: 491
Total Cats: 39
Default

Quote:
Originally Posted by Braineack View Post
Correct me if I'm wrong, but a MS running MAP alone, with a baro reading taking on startup, running on a perfect tune, then drives 5000ft. in elevation, will have leaned out AFRs until the car is reset and the thinned out air can be metered. Because that reading is part of the fuel equation.

Maybe if you turn off corrections completely you would be correct. I'm not well versed in this. But I do like that exhaust backpressure part of it. Even still, with an initial reading you'll still want to tune the non-linear table to fine tune the amount of corrections, as I'm pretty sure the default algorithum is not ideal.
This is the exact issue I've been fighting on my NA tune. When I climb altitude the car starts to run leaner and leaner. Once I cycle the ignition and restart the car everything other than idle will be rich. Something with the default algorithm is definitely off. I never take the time when I'm at the track altitude to mess with the non-linear table as I'm usually focused on the driving.
Lincoln Logs is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
Back to Stock Part Out!! Turbo Parts, MS2 Enhanced 01-05, Suspension, and MOAR! StratoBlue1109 Miata parts for sale/trade 16 10-02-2015 10:39 AM
Walbro 255lph Fuel Pump $50 lsc224 Miata parts for sale/trade 2 10-01-2015 10:17 AM
Got bad Crank Angle Sensor and Random Misfire codes, but runs fine. Greasyman General Miata Chat 2 09-28-2015 11:44 AM


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 07:19 AM.