Converter lockup and slip
The torque converter lets the engine turn while the car is stopped, but it slips, and slip is lost drive and heat. Lockup clamps it solid; slip strategy lets it slip a controlled amount on purpose. This is where street smoothness, track efficiency and drift behaviour are won or lost. Read torque setup and program tuning first.
What the converter does
Between the engine and the gearbox is a fluid coupling. At a standstill it slips completely (engine idles, car holds on the brake). As revs rise it transmits more torque, but always with some slip, which turns drive into heat. The lockup clutch mechanically bridges it so there is zero slip and 1:1 drive. The TCU decides when to lock, how hard, and whether to allow a deliberate sliver of slip.
- Locked = efficient, accurate (no slip in the number on a dyno), but harsh if locked too early or too low.
- Open / slipping = smooth and forgiving, keeps revs up in a slide, but makes heat and loses drive.
The Lock program value
Each program carries a Lock value 0-2 (see program tuning) that picks a
lockup strategy: 0 loosest (street/drift), 2 tightest (track/dyno). That value selects rows in
the lockup tables below.
When does it lock? The Lockup ON map
Lockup ON RPM/TPS (10 × 8) sets the RPM at which the converter locks, by throttle position, for
each of eight lockup strategy maps. Lower number = locks earlier (more efficient, can feel harsh);
higher = stays open longer (smoother, more heat).
This is the table decoded from the BMW E90 Petrol 8HP70 base map. Rows are the lockup strategy map, columns are throttle %, cells are the RPM at which lockup engages:
| \ throttle % | 0% | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|---|
| Lock map 1 | 1400 | 1400 | 1400 | 1400 | 1400 | 1400 | 1400 | 1400 | 1400 | 1400 |
| Lock map 2 | 1100 | 1100 | 1100 | 1100 | 1100 | 1100 | 1100 | 1100 | 1100 | 1100 |
| Lock map 3 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 |
| Lock map 4 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1100 | 1200 | 1600 |
| Lock map 5 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1200 | 1400 | 2200 |
| Lock map 6 | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | 1500 | 1700 | 1900 | 2700 |
| Lock map 7 | 1400 | 1400 | 1400 | 1400 | 1500 | 1700 | 1900 | 2300 | 2500 | 2800 |
| Lock map 8 | 1900 | 1900 | 1900 | 1900 | 2000 | 2200 | 2400 | 2800 | 3000 | 3000 |
Read it: the early maps (3-5) lock around 1000 RPM at light throttle, so the converter is solid almost all the time on the street, that is efficiency and a connected feel. The later maps (7-8) hold lockup open to 1900-3000 RPM and only lock progressively, leaving converter slip available at higher throttle, which is what you want for launch and for keeping the engine in its band.
Supporting tables:
- Lockup Hysteresis — the RPM gap between locking and unlocking, stops it hunting on/off around the threshold.
- Selector/Gear swap lockup ON RPM (8 Gear × 3) — per-gear, per-
Lock-value override of the lockup point. - Open Lockup rpm < Min. RPM Limit — force unlock below a floor so you do not stall.
Slip strategy (controlled slip)
Instead of fully locked or fully open, the converter can be held at a small, controlled slip, smooth like an open converter, but most of the efficiency of a locked one. This is the modern OEM trick and TurboLamik exposes it:
- Enable slip strategy / Enable semi slip strategy / Enable slip all the time — global slip modes.
- Enable slip P1..P8 and P1..P8 activate limited lockup slip — turn slip on per program.
- Lockup Slipt RPM (3) — the target slip in RPM (e.g. hold ~40-80 RPM of slip).
- Slip difference Multiplier, Slip Torque Pres Correction, Slip difference Max Pressure — the closed-loop gains that hold the target slip under load.
- Lockup I. / Lockup P. — the integral/proportional terms of the lockup controller.
- Lockup Slipt Warmup multiplier / Oil temp Warmup — relax slip control until the fluid is warm.
A controlled-slip setup feels glassy on the street (no lockup clunk) while still locking up for efficiency. It needs accurate torque and a bit of patience to tune the gains.
Settings by use case
| Use | Lock | Strategy | Why |
|---|---|---|---|
| Street / cruise | 0-1 | controlled slip on | smooth, no clunk, still efficient |
| Track | 2 | locked, minimal/no slip | direct drive, less heat over a session, accurate |
| Drag | 2 | locked above launch | converter slip for the launch, solid once hooked |
| Drift | 0 | loose / open | keeps revs up mid-slide, converter cushions abuse |
| Dyno | 2 | locked, no slip | no converter slip hiding in the numbers |
Heat and safety
Slip makes heat. A converter held slipping under high load, or lockup that never engages because the
ON map is set too high, will cook the fluid. Watch oil temperature (Max Oil Temp., Max Oil Temp safe mode, and Max RPM in Oil Temp safe mode back you up, the box pulls RPM if it
overheats). On track, prefer tighter lockup; for sustained slip, make sure cooling is adequate.
Sources: firmware V10.75 XDF (Lockup ON RPM/TPS, slip-strategy flags and gains as named),
the manual’s tuning pages, and 8speed.au. The example map is the
8HP70 petrol base, values vary per box, get yours from download.turbolamik.eu.