Why this page matters
The Engine Configuration node holds the basic facts about your engine: how big it is, how many cylinders it has, what order they fire in and how it breathes. The ECU uses these to work out event timing, pressure estimates and which sensor belongs to which cylinder. A wrong entry here can show up as anything from a car that won't start to a misleading channel in your logs, so it's worth two minutes of checking.
Engine information
| Setting | What it does | Our advice |
|---|---|---|
| Engine Capacity | The engine's displacement | Choose liters or cubic inches in NSP under Preferences > Units Options, then enter the real figure |
| Engine Type | Piston 4 Stroke, Piston 2 Stroke or Rotary | Nearly every car engine is 4-stroke piston. Pick Rotary for Mazda Wankels |
| Number of Cylinders/Rotors | Cylinder count, or rotor count on a rotary | A 13B is 2, not 4 |
| Compression Ratio (Nexus ECUs only) | Static compression, used to estimate cylinder pressure at TDC and produce the Estimated Cylinder Compression Pressure channel | Use the build sheet figure rather than a guess |
| Aspiration | Tells the ECU how to estimate exhaust manifold pressure if there's no EMAP sensor | See below |
| Max Cranking RPM | Below this, the engine is treated as cranking; above it, running. Default 380 rpm | Leave the default unless the engine cranks unusually fast or idles unusually low |
How aspiration affects the pressure estimate
The ECU needs an Engine Pressure Ratio, which compares exhaust and intake pressure. Without an EMAP sensor, it makes an assumption based on your aspiration setting:
- Naturally Aspirated and Supercharged: exhaust pressure is assumed to be barometric pressure.
- Turbocharged: exhaust pressure is assumed to be barometric until manifold pressure goes above atmospheric, and then it's assumed to equal MAP. That's a rough stand-in for the backpressure a turbine creates.
If an EMAP sensor is enabled, the ECU uses the real measurement and ignores this estimate. On a turbo car where accuracy really matters, that's the better route.
Engine geometry
Firing order
The Cylinder list is where the firing order goes, and it decides the sequence of injector and ignition events. Haltech's convention is simple: output number equals cylinder number. Injector 1 and ignition 1 go to cylinder 1, injector 2 and ignition 2 go to cylinder 2, and so on. Don't wire outputs in firing order and then enter 1-2-3-4. The ECU handles the sequence for you.
Worked example: a small block Chevy with firing order 1-8-4-3-6-5-7-2 gets injector 8 wired to cylinder 8 and that order typed into the Cylinder list. The ECU then fires output 8 second.
Odd fire engines and TDC angle
Odd Fire Engine is off by default, and should stay off for almost everything. With it off, the ECU assumes the cylinders fire at even intervals and calculates the angles itself. Turn it on only when your engine really does fire at uneven intervals. That unlocks a TDC Angle for each cylinder, where you enter the actual firing angle so fuel and spark land in the right place. Getting these wrong on an odd fire engine will cause misfires and poor running, so take the values from reliable engine data.
Bank info
Each cylinder can be assigned to bank 1 or 2 (two banks is the maximum). Any function that works per bank reads this, for example:
- O2 control with a sensor in each bank, so each sensor trims the right cylinders.
- Nitrous with per-bank corrections.
- Knock detection and control.
V engines like V6s and V8s have two banks. Inline engines usually have one, unless the sensors are split, such as an inline 6 with twin turbos and a wideband in each exhaust.
Common mistakes
| Symptom | Usually |
|---|---|
| Starts but runs on the wrong cylinders or backfires | Firing order entered incorrectly, or outputs wired in firing order instead of cylinder order |
| Poor starting, RPM flickers during cranking | Max Cranking RPM set too close to cranking speed or to idle |
| One bank's O2 trim pulls fuel from the wrong side | Bank assignment doesn't match which exhaust the sensor sits in |
| Rotary runs very badly | Engine Type or rotor count set incorrectly |
Next steps: set up the trigger, check dwell time and set fuel density. If you're unsure of anything on a new install, book a free consultation.
