Vehicle Speed

Where road speed comes from, plus wheel circumference and differential ratio. Get these wrong and speed-based shifting is wrong everywhere.

5 parameters: 3 documented, 2 not yet documented. 1 of the undocumented ones carry the vendor's own description and nothing else. 1 exist only on firmware 10.77.

5 parameters

Differential Ratio

# 0x6CB8 1×1

Your final drive (differential) ratio, for example 2.56 or 3.46. The TCU computes road speed from this plus the wheel circumference, and speed feeds shift points and lockup logic, so get it right after any diff change.

Speed Limit

# 0x2853 8×1

A road-speed limiter that only functions on BMW Exx-series integrations. 255 means no limit, which is how to leave it on anything else.

Detail

TurboLamik XDF

255 Off speed limit Only BMW Exx Series

From the official base maps what they contain, not what it does

Every official base map ships 255 in all 8 cells.

Address: 0x1F0E 7950
Size: 8×1 cells
Width: 8-bit
Firmware: 10.75, 10.77

Speed limit sensitive

# 0x2C4E 1×1

No explanation exists yet.

From the official base maps what they contain, not what it does

Official base maps ship 199.22 on 8HP50, 8HP51, 8HP70, 8HP75, 8HP90; 100 on 8HP45.

Detail

Address: 0x1F16 7958
Size: 1×1 value
Width: 8-bit
Firmware: 10.75, 10.77

Wheel circumference (cm)

# 10.77 only Vendor description only 0x7BCF 1×1

TurboLamik XDF

If you enter the circumference, you do not need to enter the diameter.

Detail

Address: 0xE68 3688
Size: 1×1 value
Width: 16-bit
Firmware: 10.77

Wheel diameter (inches)

# 0xB9D 1×1

Rolling circumference of a driven wheel in centimetres. Measure it at normal tyre pressure; the TCU derives road speed from this and the diff ratio. Re-check after a tyre size change.