Shift Torque Management (Cut & Blip)

Applies to: IOcan · Standalone controller. What this means

The DBW Modifier is a 1.0.17 feature, on the standalone drivers only. Version details: feature → minimum firmware.

Fast, smooth gearshifts need the engine to cooperate:

  • Cut (upshift) — engine torque is briefly reduced so the driveline is unloaded while the next gear engages.
  • Blip (downshift) — engine torque/revs are briefly raised to match the lower gear, avoiding driveline shock.

How this is done depends on the driver family.

On the OEM gateways (BMW, PDK)

The factory TCU decides when a cut or blip is needed and how strong it should be. The gateway forwards those requests on two outputs:

Output Meaning
Cut request The TCU asks the engine to reduce torque (upshift)
Blip request The TCU asks the engine to raise torque (downshift)

Route them — together with the Engine torque output — to your ECU over CAN or a pin, and configure the ECU to act on them (a torque-reduction / throttle-blip strategy, ignition retard, etc.). The ECU does the actual cutting and blipping; the gateway only relays the TCU's request. If the ECU ignores the requests, the transmission still shifts, but shift quality suffers and manual downshifts arrive without rev-matching.

On the standalone direct-control drivers

The standalone transmission drivers generate cut/blip demands themselves and offer two ways to execute them:

  • Request outputs — same as the gateways: the driver raises cut/blip request outputs and the ECU executes them.
  • DBW Modifier — the driver is wired into the accelerator-pedal circuit (pedal sensor in, throttle out) and momentarily overrides the pedal signal itself: down for a cut, up for a blip. This gives clean clutchless shifts without any ECU support, calibrated with per-gear cut/blip tables (target position, ramp-in/out and duration).

The DBW Modifier is a feature of the standalone drivers only — the 8HP and PDK OEM gateways do not include it. With a gateway, shift-time torque control is always executed by the ECU via the request outputs.