Fuel tuning on a modern diesel comes down to a handful of numbers, and one of the most overlooked is where injection actually ends. We've just built that number into ECUPlex with the brand-new EOI Calculator — so you can stop estimating it and start tuning with it.
Select your maps, and ECUPlex works out the End of Injection for you in seconds. No spreadsheets, no manual crank-angle math, no guessing where your timing lands. Just clean, repeatable results pulled straight from the data already in front of you.
What is End of Injection — and why should you care?
End of Injection (EOI) is the point in the engine cycle where fuel delivery stops, expressed in crank angle degrees relative to TDC. It isn't a value you set directly. It's the result of three things working together: your Start of Injection (SOI), the injection duration, and rail pressure — all of which shift with RPM and injected quantity.
Because EOI falls out of those inputs, it's easy to ignore. That's exactly why it bites people. You can have a perfectly reasonable SOI and a duration that looks fine on its own, but combine them at high load or high RPM and your injection event ends far later in the cycle than you intended. EOI is the number that tells you whether your fuelling is landing where the engine can actually use it — or spilling into the wrong part of the stroke.
What a bad EOI actually costs you
When injection finishes too late, the consequences aren't subtle. Fuel that's still being delivered deep into the cycle doesn't burn cleanly — it ends up washing the cylinder walls, diluting the oil, driving up exhaust gas temperatures, and leaving you with incomplete combustion and soot. On a high-output build, that's the difference between a tune that holds together and a very expensive afternoon.
The trouble is that EOI drifts as you push fuel. Raise injected quantity to chase power, and your duration grows. Grow the duration without watching the back end of the event, and your EOI quietly marches later and later until it's well outside the safe window. Most tuners only find out after the damage is done.
How the EOI Calculator fits your workflow
ECUPlex already recognises and labels the maps in your file. The EOI Calculator builds on that: point it at the relevant injection maps, and it returns the End of Injection across your operating range — so you can see at a glance where timing stays safe and where it's heading into risky territory.
- Tune safer. Spot dangerous EOI values before you flash the file, not after a teardown. Catch the operating points where your injection event runs too late and fix them while it's still just numbers on a screen.
- Work faster. Converting pulse width, rail pressure and RPM into crank angle by hand is slow and error-prone. The calculator does it instantly, every time, with no spreadsheet babysitting.
- Build with confidence. Whether you're chasing peak power or dialling in a reliable daily, knowing your EOI turns guesswork into a deliberate decision. Clean, consistent results you can actually trust.
Why we built it
ECUPlex exists to take the tedious, error-prone parts of tuning off your plate so you can focus on the decisions that matter. EOI is a perfect example: a value every serious diesel tuner should be checking, that almost nobody calculates by hand because it's a pain. Now it's one click away, sitting right inside the workflow you already use.
Try it now
The EOI Calculator is live for all ECUPlex users. Log in, load a file, select your maps, and see exactly where your injection ends — before it costs you anything.
Start tuning smarter at ecuplex.com.