Megasquirt ECU Tuning with TunerStudio

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name: megasquirt-tuner

description: Megasquirt ECU tuning and calibration using TunerStudio. Use when working with Megasquirt engine management systems for: (1) VE table tuning and fuel map optimization, (2) Ignition timing maps and spark advance, (3) Idle control and warmup enrichment, (4) AFR target tuning and closed-loop feedback, (5) Sensor calibration (TPS, MAP, CLT, IAT, O2), (6) Acceleration enrichment and deceleration fuel cut, (7) Boost control and launch control setup, (8) Datalog analysis and troubleshooting, (9) Base engine configuration and injector setup, (10) MSQ tune file analysis and safety review, (11) Any Megasquirt/TunerStudio ECU tuning tasks.

---

# Megasquirt ECU Tuning with TunerStudio

Guidance for tuning Megasquirt engine management systems using TunerStudio software.

Core Concepts

Required Fuel Equation

Megasquirt calculates fuel delivery using:

Pulse Width = Required Fuel × VE% × MAP × AFR Target Correction × Air Density × Warmup × Accel Enrichment × Other Corrections

**Required Fuel** is the base injector pulse width at 100% VE, 100kPa MAP, standard temperature.

Key Tuning Tables

| Table | Purpose | Typical Resolution |

|-------|---------|-------------------|

| VE Table | Volumetric efficiency vs RPM/MAP | 16×16 or 12×12 |

| AFR Target | Desired air-fuel ratio vs RPM/MAP | 12×12 |

| Spark Advance | Ignition timing vs RPM/MAP | 12×12 or 16×16 |

| Warmup Enrichment | Fuel correction vs coolant temp | 10-20 points |

| TPS-based Accel | Accel enrichment vs TPSdot | 10-20 points |

| MAP-based Accel | Accel enrichment vs MAPdot | 10-20 points |

Tuning Workflow

1. Base Configuration

Before tuning, verify:

2. Sensor Calibration

Calibrate sensors before tuning:

3. VE Table Tuning (Speed Density)

**Method 1: Wideband O2 Feedback**

1. Enable EGO correction with moderate authority (±15-20%)

2. Set realistic AFR targets

3. Run engine at steady state (fixed RPM/load cell)

4. Allow EGO to correct, note correction percentage

5. Adjust VE by inverse of correction (if +10% correction, increase VE by 10%)

6. Save and move to next cell

**Method 2: Calculate from Measured AFR**

New VE = Current VE × (Measured AFR / Target AFR)

**Tuning Order:**

1. Start with idle region (600-1000 RPM, 30-50kPa)

2. Light cruise (1500-2500 RPM, 40-60kPa)

3. Part throttle acceleration

4. WOT high load

5. Transition regions

4. AFR Target Table

Set targets based on application:

| Condition | Target AFR | Lambda |

|-----------|-----------|--------|

| Idle | 13.5-14.5 | 0.92-0.99 |

| Light Cruise | 14.5-15.5 | 0.99-1.06 |

| Part Throttle | 13.5-14.5 | 0.92-0.99 |

| WOT Naturally Aspirated | 12.5-13.0 | 0.85-0.88 |

| WOT Turbo/Supercharged | 11.5-12.5 | 0.78-0.85 |

5. Ignition Timing

**Base Settings:**

**Typical Spark Advance Table (Naturally Aspirated):**

**Knock Considerations:**

6. Idle Control

**Idle Valve PWM Settings:**

**Idle Target RPM Table:**

7. Warmup Enrichment

**Afterstart Enrichment:**

**Warmup Enrichment Curve:**

8. Acceleration Enrichment

**TPS-based (Alpha-N blending):**

**MAP-based (for MAP-dot systems):**

**Cold Multiplier:**

Advanced Features

Boost Control

**Open Loop:**

**Closed Loop (if supported):**

Launch Control

Flat Shift

Datalog Analysis

Key Parameters to Log

| Parameter | What to Watch |

|-----------|---------------|

| RPM | Stability, limiter hits |

| MAP | Response to throttle, leaks |

| AFR (wideband) | Deviation from target |

| EGO Correction | Should stay within ±10% |

| CLT | Reaches operating temp |

| IAT | Heat soak effects |

| Spark Advance | Matches table |

| Injector PW | Headroom, max duty cycle |

| TPS | Smooth operation, TPSdot |

Common Issues

**Lean at Tip-In:**

**Rich at Decel:**

**Idle Hunting:**

**Knock at High Load:**

TunerStudio Specific

Project Setup

1. Create new project → select firmware (MS1, MS2, MS3)

2. Load base tune (.msq file) or start from default

3. Connect to controller (serial, USB, or Bluetooth)

4. Sync with controller to load current settings

Tuning Interface

Auto-Tune

Safety Limits

**Rev Limiter:**

**Overboost Protection:**

**Lean Cut:**

MSQ Tune File Analysis

The skill can analyze `.msq` tune files to identify safety issues, optimization opportunities, and configuration problems.

Using the Analyzer

Run the analysis script on any MSQ file:

python3 scripts/analyze_msq.py your_tune.msq

Or provide the tune file content directly for analysis.

How to Provide the MSQ File

**Option 1: Paste the file content** (Recommended)

**Option 2: Upload the file**

**Option 3: Provide a file path** (if running locally)

python3 scripts/analyze_msq.py /path/to/your/tune.msq

**Security Restrictions for Script Usage:**

**Option 4: Share key sections**

If the file is large, paste specific sections you're concerned about:

Example Prompts

"Review this MSQ file for safety issues before I start my engine: [paste content]"

"Check my VE table - does anything look suspicious? [paste veTable section]"

"Analyze my ignition timing map for knock risk: [paste sparkTable section]"

"I just updated my AFR targets, review them: [paste afrTable section]"

What Gets Analyzed

**Safety Checks:**

**Configuration Review:**

**Optimization Opportunities:**

Interpreting Results

**Example Analysis Output:**

📋 VE Table
----------------------------------------
  ⚠️ VE table has very low values (15.0) - check for empty/untuned cells
  📊 12 cells have >30% jumps from neighbors - consider smoothing
  ✓ VE table range: 15.0 - 105.0 (avg: 62.3)

📋 Ignition Timing
----------------------------------------
  ⚠️ High ignition advance (48°) - verify on dyno with knock detection
  ✓ Spark advance range: 8° - 48° BTDC

SUMMARY
============================================================
🚨 CRITICAL ISSUES: 0
⚠️  WARNINGS: 2
✓ Suggestions: 4
ℹ️  Notes: 1

Common Issues Detected

**High Priority:**

**Medium Priority:**

**Low Priority:**

Tune Review Workflow

1. **Before First Start:**

```

You: "Review this base tune before I start the engine"

AI: [Runs analysis, flags safety issues]

```

2. **After Changes:**

```

You: "I just updated my VE table, check it"

AI: [Analyzes for anomalies, suggests smoothing]

```

3. **Before Dyno/Track:**

```

You: "Review my tune before high load testing"

AI: [Checks timing, AFR, safety limits, injector headroom]

```

Reference Materials

For detailed documentation, see:

Quick Reference Formulas

**Injector Duty Cycle:**

DC% = (Injector PW / Injection Period) × 100

Keep under 85% for safety margin.

**Required Fuel Calculation:**

Required Fuel (ms) = (Engine CC × 5) / (Number of Injectors × Injector CC/Min) × 2

(The ×2 accounts for 2 rotations per cycle)

**Airflow Estimation:**

MAF (g/s) ≈ (RPM × Displacement × VE% × MAP/100) / (2 × 60 × R × Temp)

Safety Checklist

Before starting engine:

During tuning: