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Idle requested RPM (scanner) vs Target idle RPM (calibration)
Yesterday, I was trying to lower my idle speed on TunerCat from 675 rpm to 625. But when I burned the chip and put it in, the scanner was showing that the computer was still requesting a 675 rpm idle speed. I repeated the process several times but could not get the computer to alter it's idle speed request. I also went back and cleaned the IAC, then changed to another IAC I had lying around, and performed the manual idle speed adjustment multiple times. No matter what I tried, it would not drop down past 675 rpm.
Re: Idle requested RPM (scanner) vs Target idle RPM (calibration)
Quote:
Originally posted by Pro-Tour71 Yesterday, I was trying to lower my idle speed on TunerCat from 675 rpm to 625. But when I burned the chip and put it in, the scanner was showing that the computer was still requesting a 675 rpm idle speed.
Which ECM & maskId? On most setups there are different requested idle speeds according to coolant temp and the drv/neut switch position.
Originally posted by Pro-Tour71 Yeah, that would help woundn't it?
It's a 7730 ECM and (not sure of the mask I.D.) it's based on an AUJP calibration.
I tried changing the "add rpm to Park/Neutral" value to zero. But the ECM wouldn't accept change that either.
OK, $8D it is. There are several items that affect the desired idle speed: coolant temp, prk/neut, battery voltage, hot restart, and A/C on. Here is a code snippet of the desired idle speed calc:
Code:
LDAA L005D ; FLT COOLANT TEMP
LDX #L8632 ; IAC CMD SPEED vs COOL TABLE
JSR LE3D0 ; 2D LOOK UP, NO OFF SET
TAB ;
BRCLR L00FE,#$80,LC269 ; BR IF NOT b7, PK/NEUT, 1 = NEUT
; (IAC Md Wd #2)
; .... else
ADDB L862E ; 100 RPM ADDED IF IN PK/NEUT
;
LC269: BRSET L00FD,#$80,LC270 ; BR IF AC STATUS OFF
ADDB L8630 ; 12.5 RPM ADDED IF A/C ON
;
LC270: BRCLR L003A,#$08,LC27E ; HOT RE-STRART RETARD OFF
LDAA L0063 ; Linear MAT value (from tbl)
LDX #L8673 ; HOT RESTART CMD SPEED vs MAT TBL
JSR LE3D0 ; 2d LOOK UP, NO OFF SET
ABA ;
TAB ;
;
LC27E: ADDB L01B5 ; DIFF DESIRED RPM FOR LOW BATTERY
From that the table addresses can be found (the L86xx numbers).
Code:
L8632 ; IAC CMD SPEED vs COOL TABLE
L862E ; 100 RPM ADDED IF IN PK/NEUT
L8630 ; 12.5 RPM ADDED IF A/C ON
L8673 ; HOT RESTART CMD SPEED vs MAT TBL
L8693: FCB 120 ; ADD O.S. TO DESIRED RPM IF BATT =< 12.0 V
L8694: FCB 135 ; SUB O.S. TO DESIRED RPM IF BATT > 13.5 V
;
L8695: FCB 5 ; ADD OFFSET IF BATT LO 5 SEC'S
L8696: FCB 1 ; ADD 12.5 RPM TO OFFSET IF BATT LO
;
L8697: FCB 20 ; CLR BATT IAC WHEN Vss > 20 MPH
;
L8698: FCB 8 ; LIMIT IAC OFFSET FOR LO BAT TO 75 RPM.
; ARG = RPM/12.5
From the looks of it the idle spd starts with the table value at L8632 vs coolant. Then each of the (edit: make that. . . ) 4 others just add to that idle spd to increase it.
Originally posted by Pro-Tour71 I don't recognize some of those parameters from TunerCat.
All I can locate that affect RPM at idle operation are:
Idle speed vs Coolant temp - 625 rpm
Add to RPM in Park/Neutral - 0
Add to RPM with A/C on - 0 (no A/C on my car)
The idle speed vs coolant should be a table that covers a range of coolant values. Make sure that the coolant is at the proper temperature for the desired idle spd.
OK to the prk/neut & A/C, eliminates those variables. That leaves the battery voltage and hot restart MAT corrections to check. Can either add the parameters or use a hex editor to check/change them.
Originally posted by Pro-Tour71 Thanks for the info. But I haven't delved deep enough into the program to know how to do Hex editing.
What is entailed in that?
Best bet would be to ask Tunercat to add the idle variables. They are good about adding items to the TDF files.
For hex editing, search the diy-efi archives. It isn't something to be taken lightly. You'll neeed to do conversions yourself and plug them into the proper EPROM bin file location.
Originally posted by RBob The idle speed vs coolant should be a table that covers a range of coolant values. Make sure that the coolant is at the proper temperature for the desired idle spd.
RBob.
Off topic: Is this what you would change to get the car into closed loop earlier if you have a lower temp. stat?
