How to MegaSquirt Your Honda or Acura

Models Covered

  • 1992–2000 Civic/Del Sol/Integra (Honda & Acura)
  • 1992–2001 Prelude
  • 1992–2002 Accord 4‑cylinder
  • Many OBD0 Hondas (varies by model)

Engines commonly supported include D16, B16A, B18C, H22A, and F23A. This guide does not cover later coil‑on‑plug systems (e.g., S2000, D17 Civics).

What’s Covered

Our install articles focus on the most platform‑specific step: ignition control.

Honda Distributor Signals (VR)

1990s Honda/Acura distributors use three VR sensors:

  • CYP/CYL (1 pulse per cam rev)
  • TDC (4 pulses per cam rev) — use this one
  • CKP (24 pulses per cam rev)

Many F/H‑series place TDC/CKP at the crank. For MegaSquirt the simplest/most robust approach is to use the TDC sensor only and ignore CKP/CYP. Typical TDC wire colors: orange/blue (+) & white/blue (−) or green (+) & red (−); confirm in the factory diagram.

Using MegaSquirt‑II (V3.0/V3.57) with the Honda Ignition Module

MS‑II PCB V3.0 mods

  • Build VR conditioner; TachSelect→VRIN, TSEL→VROUTINV; R52/R56 fully CCW.
  • Jumpers: JS10→IGBTIN and IGBTOUT→IGN.
  • Install a TIP120 (or BIP373) in Q16 as a switching transistor (not direct‑coil drive).

MS‑II PCB V3.57 mods

  • Jumpers: JP1=1–2, J1=5–6; R52/R56 ≈ five turns CCW.
  • JS10→IGBTIN; Q16: TIP120 (or BIP373) used as a switch.

External ignition wiring (MS2)

  • TDC (+) → DB37 pin 24; TDC (−) → ground (use harness shield as ground if available).
  • Honda ignitor input → DB37 pin 36.

TunerStudio ignition configuration (MS2)

  • Trigger Offset ≈ 10° (verify with light; see “Trigger Offset” below).
  • Ignition Input Capture = Falling Edge
  • Cranking Trigger = Trigger Rise
  • Coil Charging Scheme = Standard Coil Charging
  • Spark Output = Going High (Inverted)
  • Dwell = 3.0 ms

Setting Trigger Offset (all versions)

  1. Warm the engine and hold a steady idle.
  2. In TunerStudio → Tools → Trigger Wizard, set a fixed timing (e.g., 10°–16° depending on service‑manual base timing) and adjust Trigger Offset (and/or rotate the distributor) until the timing‑light reading matches the wizard’s value.
  3. Return to mapped timing (Fixed Angle = −10 on MSnS‑E).

IAC Valves (PWM)

  • Honda PWM IAC runs ≈ 500 Hz.
  • MS1/Extra: set frequency to 20 (per its scaling).
  • MS2 (B&G code): enter 500 Hz directly.
  • V3.57: no IAC hardware mods needed; V2.2/V3.0: add TIP120 at Q4 (see MK‑PWMIAC kit).

VTEC Control

VTEC solenoid is 12V powered by the OE ECU. Easiest retrofit is to add a relay control output from MegaSquirt (e.g., MK‑RelayCtrl) to switch power to the VTEC circuit.

  • MS2: RPM + TPS (and other conditions).

Advanced non‑relay transistor circuit is also possible: connect the node labeled “To MS CPU” to a spare processor output configured for VTEC control.

Suggested Parts (DIYAutoTune / AMP EFI)

Legal/Emissions: For off‑road/closed‑course use where required. Verify local compliance and any warranty impacts before modifying engine controls.