The pinout planner for standalone swaps
Pick the right ECU.
Plan every pin.
Most people choose a standalone ECU backwards: brand first, build second. StandaloneHQ does it the other way round. Describe the engine and how you’re running it, and it counts the inputs and outputs the build actually needs, shows which wire-in ECUs clear that bar, and lays the wiring out pin by pin.
What it does
An ECU is a box with a fixed number of the right – or wrong – kinds of pin
Whether one fits your swap comes down to a single question: does it have enough of the right types of input and output for what your engine needs, with a little headroom? Spec sheets flatten that into big friendly numbers. The planner unflattens them.
Counts are easy. Types are the trap.
Eight injector drivers is only useful if they are the peak-and-hold kind your low-impedance injectors want. Smart LS coils and dumb Coyote coils need different ignition outputs. The planner tracks the type of every channel, not just the count.
Triggers are not digital inputs
Crank and primary cam need dedicated trigger inputs, and most ECUs have two. Extra cam sensors on a four-cam VVT engine run on ordinary digital inputs. Counting them all as triggers rules out perfectly good ECUs; the planner knows the difference.
Every sensor eats more than one pin
A three-wire sensor takes a signal input, a tap off a 5V reference, and a tap off a sensor ground. Stack enough of them and you run out of reference capacity before you run out of analogue inputs. That fan-out is budgeted, not guessed.
How it works
Choose the ECU last
Three steps, in this order. Skip the middle one and you find out you are two outputs short halfway through the wire-up, which is a bad time to find out anything.
Describe the build
Cylinders and layout, port or direct injection, sequential or batch, coil-on-plug or wasted spark, how many cams are variable, NA or boosted, and the extras: flex fuel, drive-by-wire, traction control, a PDM.
Get the I/O tally
The planner turns those decisions into a needs list: how many of each output and input type, plus trigger, 5V-reference and sensor-ground budgets. This is the number that decides your build, not the one on the box.
Shortlist, then plan the pins
See which ECUs clear the bar with headroom and where each falls short. Pick one, and the planner maps every signal to a connector pin so you can wire from the sheet instead of the forum.
Guides
Read before you buy
The same framework the planner runs, written out so you can follow it on paper. Start at the top; the order is the order you will meet each decision in.
How to Choose a Standalone ECU for Your Engine Swap: A Practical Framework
A builder's framework for choosing a standalone ECU for an engine swap: define the build, count the I/O it actually needs, then shortlist. No…
Read the guide → Guide 02 · Choose & selectStandalone Wire-In vs Plug-In ECUs: Which Is Right for Your Build?
A straight comparison of wire-in and plug-in standalone ECUs – cost, effort, reliability, reversibility and tuning ceiling – with a decision guide for your…
Read the guide → Guide 03 · Choose & selectPlug-In ECUs Explained: When the Factory Connector Is the Smart Choice
How plug-in standalone ECUs actually work: adaptor boards, what you inherit from the factory harness, the real limits, and which platforms are well-served.
Read the guide →Stop counting pins on a napkin
The planner is free, runs in the browser, and keeps nothing about you. Describe the engine, get the tally, pick the box.