Rom address for value in km/h that fuel cut can occur?

RB30-POWER · Post by **RB30-POWER** » Tue Sep 11, 2007 6:28 pm

Hey Guys,

Im fairly sure there is a value in the bin file/rom somewhere that signifys that the fuel cut on decel (closed tps) can only occur when vehicle is travelling above set speed in km/h.

Once the speed parameter is met, then it refers to the rpm tables, that are already known and in the software.

Does anyone know what the location of this is at all?

Im fairly sure on the auto roms its around 60-70km/h (can't recall exactly)

Manuals have the same, but unsure of what speed, may be lower.

Regards
Mick

RB30-POWER · Post by **RB30-POWER** » Thu Sep 13, 2007 7:16 pm

EDIT: Its actually 8km/h according to the manual.

Must have just seemed like 60km/h because of the torque convertor not locked and dropping rpm under fuel cut rpm figure.

But if anyone knows where that 8km/h address is in the bin let me know.

Regards
Mick

Matt · Post by **Matt** » Fri Sep 14, 2007 1:16 am

Checks against speed is found and uses the folllowing comparison three times in the code. The one you are looking for...

9CD6 : bne L9D2E
9CD8 : ldaa X000C (Speed)
9CDA : cmpa XBF85 (Speed limit check)
9CDD : bcs L9D05 (skip)
9CDF : ldx #$BE40 (Fuel cut)
9CE2 : jsr LA8A1 (lookup table)

XBF85 address value is 0x04 hex VLT but you mulitply the speed x 2 to get KM/h so this is it

SPEED1_LIMIT,&H3F85,2,1,1,2,Speed based fuel cut check

(XBF4F is the address for R31)

datsunboy · Post by **datsunboy** » Fri Sep 14, 2007 12:25 pm

is there any problems with not running a speed sensor?
I had a CA in a Datsun 1600, and swapped the electronic speed sensor out for a cable one.
would this mean that the ECU will never cut fuel on decel?
other than economy....any problems with that?

Matt · Post by **Matt** » Fri Sep 14, 2007 9:37 pm

shouldn't be any probs. The ECU uses default (limp) values for most sensors when they are out of range (not detected) and then flags a DTC code which flashes out on the LEDs

FYI the first entry for most temperature based tables is the default temp based value when no temp sensor is available

Matt · Post by **Matt** » Fri Sep 14, 2007 9:39 pm

shouldn't be any probs. The ECU uses default (limp) values for most sensors when they are out of range (not detected) and then flags a DTC code which flashes out on the LEDs

FYI the first entry for most temperature based tables is the default temp based value when no temp sensor is available

RB30-POWER · Post by **RB30-POWER** » Sat Sep 15, 2007 2:53 pm

Well i set the value to 0km/h, but it didn't fuel cut when speed signal was not present.

Long story short, vl's have a cable that goes from box to dash cluster, cluster head then has a setup to produce a speed signal for the ecu and cruise control module etc.

I think the dash has a bad solder joint, but can't really be stuffed pulling it out, sometimes the speed signal works (fuel cuts on decel as per normal) when its not present the ecu does not fuel cut and cruise control does not work etc on the car.

I thought setting the value to 0km/h would make it fuel cut all the time regardless of the speed signal.

Did not fuel cut however with this value changed.