Step 54 of MS assembly - 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 11-04-2007, 01:01 AM   #1
Elite Member
Thread Starter
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default Step 54 of MS assembly

Im up to the part of the MS install R4 and R7.

The "how to" says to remove R7 if sharing the stock CLT sensor. Braineak mentioned in some thread that it threw off the calculation on his car. But my question is, how does it even work in the car if the ECU doesnt even register the information sent to it by the Megastim when monitored in Megatune if the resistor is not in place.

Wouldnt it be smarter to follow the megamanual and get the appropriate resistor for a mazda? 2.2k ohm?

Now R4 refers to the AFM supposedly according to the "how to". How do we know that R4 is appropriate for our cars? I know we don't use AFM because of MAP, but I am curious.

Is there a separate table somewhere to determine the appropriate bias resistor for that? Why even install the resistor if we dont use it?

The megamanual all in all is very confusing about these two because it refers to them both together in one step and then links them as being responsible for the CLT.
Saml01 is offline   Reply With Quote
Old 11-04-2007, 01:54 AM   #2
Elite Member
Thread Starter
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default

http://www.megamanual.com/v22manual/sharesen.htm

Looks like R4 is for AIT not AFM, which answers my second question. That would mean the one sold by DIYautotune has the appropriate resistance to match the 2.49k ohm bias resistor.

This link also says to leave R7 out if sharing, but I still dont understand how its supposed to work.
Saml01 is offline   Reply With Quote
Old 11-04-2007, 02:41 AM   #3
:(
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,281
Total Cats: 2
Default

R7 splits the signal but if you are sharing already you don't need it resplit. any way you cut it my max temp with r7 installed was 74 C with r7 out it has gone to 104 or so,
magnamx-5 is offline   Reply With Quote
Old 11-04-2007, 11:23 AM   #4
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,842
Total Cats: 1,787
Default

when you finally flash the firmware you have to setup your intake and coolant sensor resistance values.

easytherm is already preloaded with the default values for the sensors, so with the additional resistor added inside MS, the bias resistance has changed and MS will display the temp value incorrectly. You can leave it in and then figure out what the bias resitance with R7 installed is.

and yes, R4 is for the AIT.

these two resistors are specifically the intake and coolant temp bias resistors.
Braineack is online now   Reply With Quote
Old 11-04-2007, 12:03 PM   #5
Elite Member
Thread Starter
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default

Quote:
Originally Posted by Braineack View Post
when you finally flash the firmware you have to setup your intake and coolant sensor resistance values.

easytherm is already preloaded with the default values for the sensors, so with the additional resistor added inside MS, the bias resistance has changed and MS will display the temp value incorrectly. You can leave it in and then figure out what the bias resitance with R7 installed is.

and yes, R4 is for the AIT.

these two resistors are specifically the intake and coolant temp bias resistors.
So what are the bias resistors supposed to compensate for?

Quote:
Originally Posted by magnamx-5 View Post
R7 splits the signal but if you are sharing already you don't need it resplit. any way you cut it my max temp with r7 installed was 74 C with r7 out it has gone to 104 or so,
Splits it for what reason? I don't understand. If the AIT that we install is not shared with anything, why does the MS need to split it internally?
Saml01 is offline   Reply With Quote
Old 11-04-2007, 01:42 PM   #6
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,842
Total Cats: 1,787
Default

the bias resitors move the reference voltage around, iirc.

Esaytherm generates a table with your giving inputs so MS can correctly understand what the resistance value it sees means.

example:
HTML Code:
; Generated 05/07/2004 22:21:41 by MStoolsII 
; GM #12146312 
; Standard GM type Coolant Thermistor for Megasquirt 
; Computed Steinhart-Hart coefficients: A=0.00162549  B=0.00019531  C=3.00954e-07
;	 0 Fahrenheit = 25000 ohm
;	 100 Fahrenheit =  1800 ohm
;	 210 Fahrenheit =   185 ohm
; For use with  2490 ohm bias resistor installed at R7.
THERMFACTOR:
		;	 ADC 	 Fahrenheit - Celcius - resistance in ohms
	DB	210T;	   0 - sensor failure, use limp home value.
	DB	255T;	   1	  408 	 209 	     10 ohms
	DB	255T;	   2	  353 	 178 	     20 ohms
	DB	255T;	   3	  323 	 162 	     30 ohms
notice the bias resistance statement? it's looking for a specific bias, when you're sharing that signal with the stock ECU the bais resistance is raised, becuase the stock ECU has it's own resistor. So the scale on which you generated your table will be off.

what will happen if you dont remove r7 and share the coolant sensor with the stock ECU is your temps will display 30*F cooler than they really are.
Braineack is online now   Reply With Quote
Old 11-04-2007, 03:01 PM   #7
Elite Member
Thread Starter
iTrader: (9)
 
Saml01's Avatar
 
Join Date: Jul 2007
Location: NYC
Posts: 5,730
Total Cats: 2
Default

Thats pretty awesome.

So I don't have to make a separate thread. How come Q9 and Q12 have to be on mica insulators?
Saml01 is offline   Reply With Quote
Old 11-04-2007, 03:18 PM   #8
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,842
Total Cats: 1,787
Default

I know those will get grounded out without the insulators and the MS will not work.
Braineack is online now   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Toyota Pickup Engine Swap B.S. Monk Build Threads 24 12-11-2016 03:21 PM
Need help - Stock Balancer and Fastforward overlay pulleys Frank_and_Beans Supercharger Discussion 13 09-12-2016 09:17 PM
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
elesjuan's mediocre 95 Miata adventure (google fiber edition) elesjuan Build Threads 8 02-16-2016 09:36 PM
Nuke Mars! Joe Perez Current Events, News, Politics 8 09-30-2015 05:41 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 04:22 PM.