What the table controls
When NSP's Transmission Control function is in the middle of a shift, the Shifting Target table sets the line pressure the ECU aims for. Line pressure is what clamps the clutch packs and bands. More pressure applies them harder and faster; less lets them slip in more gently. Once the shift finishes, control goes back to the In Gear Target.
This table sets the pressure you want. Turning that into solenoid duty is the job of Shifting Base Duty Cycle, so make sure that's set up first.
Where to get your starting numbers
In order of preference:
- A base map for your transmission. Import its target pressure tables.
- Your transmission builder. If the unit has upgraded clutches, bands or valve body parts, ask the builder what pressures it wants. Their advice beats any generic map.
- A tuned car with the same transmission, or pressures from the OEM service manual.
- A base map for a different transmission. Better than guessing, but it can cause harsh shifts or extra wear, so treat it as a rough start and watch closely.
How we tune it
- Start high and come down. Too much pressure feels harsh but is easy on the clutches. Too little means slipping, heat and wear. Begin on the high side and work down until shifts feel right.
- More torque needs more pressure. Tune across load, not just at one throttle position.
- Harsh doesn't always mean too much. In most units, more pressure gives a quicker, firmer shift. But if pressure is too low, the shift can drag, slip and then bang in, which also feels harsh. Log it before you assume.
- With no relevant base map, start very high and lower pressure step by step until quality gets worse or the engine flares (RPM rising when it shouldn't). Then raise it back to where shifts were clean.
- Slipping between shifts is a different table. If it slips while holding a gear, raise the in-gear pressure.
Reading a shift in the logs
Pressure and time work together. If the shift can't finish in the time the ECU allows, you get a sloppy shift regardless of feel. Here's how to check:
- Log Engine RPM alongside three transmission channels: Transmission Control Shift Progress, the current Transmission Control State, and how long it has been in it (Transmission Control State Time).
- On an upshift, find where RPM starts dropping and where it settles at the new gear's speed.
- Compare that with Shift Progress. If it hits 100% and the state changes while RPM is still falling, the transmission hasn't finished shifting when the ECU thinks it has.
- Fix it by raising the Shifting Target, lengthening the Shift Duration, or both, until the shift completes in time.
Erring long on Shift Duration is fine. The only cost is that the next shift can't begin until the ECU considers this one finished and the post-shift lockout has passed.
Troubleshooting
| Symptom | Usually |
|---|---|
| Hard, banging shifts | Shifting pressure too high, or so low the shift slips then grabs; check logs |
| RPM flares during the shift | Shifting pressure too low for the torque |
| Shift progress ends before RPM settles | Shift Duration too short or Shifting Target too low |
| Slipping while cruising in gear | In-gear target too low, not this table |
FAQ
Can I use a base map from a different transmission?
As a last resort, yes. Start conservatively and watch for harsh shifts or flares.
Why does the shift feel different cold?
Fluid viscosity and solenoid behavior change with temperature. Temperature correction handles that.
More background is in line pressure control.
