Idle requested RPM (scanner) vs Target idle RPM (calibration)

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Jun 11, 2003 | 08:15 AM

ULTM8Z

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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.

Anybody experience anything like this?

Jun 11, 2003 | 09:13 AM

RBob

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From: Chasing Electrons

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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.

RBob.

Jun 11, 2003 | 09:25 AM

ULTM8Z

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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.

Jun 11, 2003 | 11:52 AM

RBob

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Quote:

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.

RBob.

Last edited by RBob; Jun 11, 2003 at 12:20 PM.

Jun 11, 2003 | 12:36 PM

ULTM8Z

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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)

Jun 11, 2003 | 01:09 PM

RBob

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From: Chasing Electrons

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Quote:

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.

RBob.

Jun 11, 2003 | 01:26 PM

ULTM8Z

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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?

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Jun 12, 2003 | 09:07 AM

RBob

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From: Chasing Electrons

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Quote:

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.

RBob.

Jun 12, 2003 | 10:46 AM

My90Iroc

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From: E. Patchogue, NY

Car: '90 Iroc

Engine: 305 TPI

Transmission: 5 spd

Quote:

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?