Modifying As-Built Data Guide

[fionic]

Two more to add to the sheet:

Disable Door Ajar Chimes
IPC 720-01-02 xx0x xxxx

Rear Axle Ratio
BCM 726-12-01 xxXX xxxx xxxx
where XX =
3B : 3.15
4B : 3.31
63 : 3.55
75 : 3.73
9A : 4.10

that axle ratio was able to be written?

good find on the disable door ajar chime! weird that it's in the ipc.

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[Spart]

Two more to add to the sheet:

Disable Door Ajar Chimes
IPC 720-01-02 xx0x xxxx

Rear Axle Ratio
BCM 726-12-01 xxXX xxxx xxxx
where XX =
3B : 3.15
4B : 3.31
63 : 3.55
75 : 3.73
9A : 4.10

Interesting that the hex values are increasing even if it doesn't seem at first to be linear with the diff ratio. Have you tried plugging in other values to see if you can do in between sizes? That would be particularly useful for people who run a different size tire from factory.

 

[fionic]

Interesting that the hex values are increasing even if it doesn't seem at first to be linear with the diff ratio. Have you tried plugging in other values to see if you can do in between sizes? That would be particularly useful for people who run a different size tire from factory.

it's literally ratio in hex, so it could work.

3.85 = x81
5.00 = xF4

etc

edit: looks like it is the first half word.

nnnn xxxx xx

where

nnnn = ratio in hex

so
3.15 = 013B
3.31 = 014B
3.55 = 0163
3.73 = 0175
4.10 = 019A
8.99 = 0383 (if it accepts it)
etc.

 

[Spart]

Ahh interesting. I wasn't looking at the right decimal place.

 

[plc268]

Most do it with a tune. You don't have to, but your odo and mileage will become slightly incorrect if you don't cater for the ratio change.

Cant do it with a tune, afaik. You have to do it with a whipple flare wheel/axle tool, which basically does the same thing you listed.


You should be able to change the tire size as well. I know with the whipple tool, you change it by changing the revs per mile. Don't know how easily that'll translate.

 

[gt_stang]

that axle ratio was able to be written?

good find on the disable door ajar chime! weird that it's in the ipc.

Yes, writable, tested switching from 331 to 355 and 373.

 

[gt_stang]

Cant do it with a tune, afaik. You have to do it with a whipple flare wheel/axle tool, which basically does the same thing you listed.

With an sct/bama x4 you can.

 

[Redraven571]

This thread talks about the Pedal Commander and how, for $300, it can alter throttle response to make the car more responsive.

Think it can be done via Forscan?

 

[fionic]

This thread talks about the Pedal Commander and how, for $300, it can alter throttle response to make the car more responsive.

Think it can be done via Forscan?

perhaps maybe if we can figure out where it is maybe maybe

 

[Freman]

3.15 = 013B
3.31 = 014B
3.55 = 0163
3.73 = 0175
4.10 = 019A
8.99 = 0383 (if it accepts it)

Anyone know if the ratios are from a pre-set list so-to-speak. Or could you program it to any number you like. If it takes any number then would it not be feasible to fine tune this to make the speedo much more accurate?

 

[Spart]

Anyone know if the ratios are from a pre-set list so-to-speak. Or could you program it to any number you like. If it takes any number then would it not be feasible to fine tune this to make the speedo much more accurate?

Curious about this too.

I am highly annoyed by factory speedos that purposely read fast. BMW is a huge offender here - I've observed 4% off even though the odometer was dead nuts on.

That said, my 17 GT W/PP is dead on from the factory with the Pirellis. If I decide to change tire sizes down the road, though, it would be nice to know that I can program the car to match - even it it's just 1% off.

 

[fionic]

try it out

 

[Spart]

try it out

Weather's been shitty and the car's been in the garage. Finally got it out this afternoon after I installed a Steeda clutch spring but more rain just came through.

My weekend is shot, if there's good weather next week I can probably try it out though. I'd want to compare my speedo against GPS to see if the settings actually make the correct difference.

 

[Cobra Jet]

I have not seen this one asked yet:

Can the speed limiter be adjusted?

 

[fionic]

I have not seen this one asked yet:

Can the speed limiter be adjusted?

I think this one is in the PCM, so a tune prob only option.

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