Why the torque model exists
Factory cars share torque information between modules constantly. An automatic transmission asks the engine to back off torque for a moment during a shift so the clutches don't take a beating. A traction control module asks for a larger cut when a wheel starts spinning. Some ABS and stability systems also want to know how much torque the engine is producing so their own logic works.
When a Haltech Elite replaces the factory ECU, it has to take over both halves of that job: report believable torque figures, and reduce torque by the amount that's asked. The torque model is how it does that. If it's set up badly, shifts can feel harsh, stability systems can misbehave, and traction control may cut too little or far too much. That's why this is one of the areas we don't rush.
How a torque reduction is applied
Modules can send two kinds of message: a reduction (take away this much) and a limit (don't go above this much). If more than one is active, the ECU acts on whichever results in the lowest torque. It then gets there using retard, cylinder cut or both:
- Ignition retard is smooth and quick to recover, which suits small reductions like a gearshift.
- Cut drops a share of ignition or injection events. It's coarse, but it can remove a lot of torque, which suits big requests like a traction control intervention.
Settings tab
| Setting | What it does | Our advice |
|---|---|---|
| Ignition Correction Enable | Lets the ECU retard timing in response to a request, and adds the Ignition Correction table to the navigator | On for almost every car that uses the torque model |
| Cut method: Disable | No cut is ever used, only retard (if enabled) | Only when the requests are always small |
| Cut method: Ignition | Drops ignition events to remove torque | The usual choice |
| Cut method: Injection | Drops injection events to remove torque | Use when your setup calls for a fuel cut instead |
| Torque Strategy | Picks which engine generation's torque strategy to use | Match the engine that's actually in the car, which matters on swaps |
The three tables, in the order you tune them
1. Engine Torque
Found under ECU Navigator > Torque Model > Engine Torque. This is the ECU's estimate of how much torque the engine is making for a given amount of air. Everything else in the torque model depends on it, so it gets tuned first.
The intended axes are Load - Normalised Air Mass Flow across the top and RPM up the side, though you can pick any channel, such as manifold pressure, mass air flow or throttle position. To change axis values, select the table and press F3. Editing an existing axis site rescales the table so its shape is preserved, which is handy when you want to move breakpoints without starting over.
What a good table looks like:
- With normalised air mass flow as load, the map should be smooth and close to a straight line. On other load axes it won't be linear, and that's expected.
- Torque falls off sharply at low load and low rpm.
- No cell should ever be negative.
Here's the catch. Some transmissions or chassis modules won't behave until the ECU reports sensible torque, so you may need to fill in rough estimates before you can even start fuel and ignition tuning. Once the engine tune is done, replace those estimates with measured figures from a dyno.
This table can't be tuned accurately on the road. If you're on a chassis dyno, make sure it's set up with the right tire size, final drive and gear ratio so it calculates engine torque, not just wheel torque. Bad dyno setup means bad torque numbers, and every module relying on them inherits the error.
2. Ignition Correction
Found under Torque Model > Ignition Correction. This sets how much timing is pulled for a given reduction request. It's meant to use Torque Reduction Total (Nm) or Torque Reduction Percentage as an axis, though you can change both axes to other channels.
Because retard keeps the engine running smoothly, this table should carry the small requests: shift torque management, gentle stability interventions and the like.
3. Cut Percentage
Found under Torque Model > Cut Percentage. Same idea and the same suggested axes, but the output is the share of cylinder events to cut. It supports up to 3D mapping. Haltech's default layout leaves this at zero for small requests and only brings cut in for large ones, such as a traction event. That's the balance we keep: retard for finesse, cut for force.
Testing reductions without the other module
You don't need a transmission shifting or a wheel spinning to tune the retard and cut tables. Under Torque Model > Tuning there are two test values:
| Setting | What it does | Resets to |
|---|---|---|
| Temporary Torque Reduction | Sends a reduction request of the amount you enter | 0.0 Nm on every ECU restart |
| Temporary Torque Limit | Sends a limit request at the value you enter | 3000.0 Nm on every ECU restart, which is out of reach for most engines, so nothing happens |
Both are always active, which is why their defaults are set to values that do nothing. Leave them at those values when you're finished.
Worked example
Here's how a session typically goes for us once the Engine Torque table is tuned from dyno data:
- Hold the engine at a steady load and rpm on the dyno and note the measured torque.
- Enter a small value in Temporary Torque Reduction, a modest fraction of that torque.
- Watch the dyno. If torque drops by less than you asked for, add retard in that part of the Ignition Correction table; if it drops by more, take some out.
- Repeat with larger reductions. When retard alone can't get there, or would need unreasonable timing, bring in Cut Percentage.
- Test the limit side with Temporary Torque Limit set a little below the measured torque, and confirm the engine settles at that figure.
- Set both test values back to their defaults.
The goal is simple: the torque the dyno measures should drop by the amount the ECU was told to remove.
Troubleshooting
| Symptom | Usually |
|---|---|
| Harsh or flared automatic shifts | Engine Torque table inaccurate, or retard not delivering the requested reduction |
| Traction control bogs the car badly | Cut Percentage too aggressive for the size of request |
| Traction control barely helps | Cut method disabled, or cut not reached for large requests |
| Engine won't make power after tuning | Temporary Torque Limit left low or Temporary Torque Reduction left non-zero (both stay active until changed or the ECU restarts) |
| ABS or stability warning lights | Reported torque unrealistic, often negative cells or rough placeholder values |
Torque model FAQ
Do I need the torque model on a manual car?
Only if something in the car asks for engine torque or torque reductions, such as an ABS or traction control module. If nothing does, you can leave it alone.
Can I use estimated torque numbers?
As a starting point, yes, and sometimes you have to so the car will drive. Replace them with measured values once the tune is finished.
Retard or cut for torque reduction?
Retard for small, frequent reductions because it's smooth. Cut for large reductions because it's powerful. Most cars use both, split by request size.
Related reading: boost control, transient throttle and deceleration. Working on a transmission swap? Get in touch and we'll help you plan the torque side.
