What Quick-Tune actually does
Every cell in the Nexus Base Fuel Tuning table is the ECU's starting point for fueling at that rpm and load. If the engine runs leaner or richer than the target lambda for that point, the cell is wrong. Quick-Tune works out how wrong from the difference between target and measured lambda, then rewrites the cell so the next time the engine is there, it lands on target.
If that sounds like short-term fuel trim, it's close. The difference is that trims correct fueling on the fly and forget it, while Quick-Tune writes the fix permanently into the base table.
It has limits, and they matter:
- It only edits the Base Fuel Tuning table. It won't touch corrections, transient fuel or anything else.
- It needs a working, correctly set-up wideband O2 input. On Nexus that's usually a WB1 or WB2 CAN controller.
- It's only as good as your setup. Engine size, injector data and every other fuel-related setting need to be right first, or Quick-Tune will "correct" around the mistake.
- It's a roughing-in tool, not a tune. Ignition timing, transients, cold start and engine safety still need a human.
Two ways to use it
| Instant (Q) | Cell trace (T, then R) | |
|---|---|---|
| What it corrects | One cell: the one the engine is in right now | Every visited cell inside the range you select |
| Data used | A single snapshot of target vs measured lambda | Up to the last 2 seconds of samples per cell, averaged |
| Best for | Steady-state dyno work, one cell at a time | Ramp runs, street drives, covering a lot of the map quickly |
| Main risk | Correcting from a moment that wasn't stable | Applying corrections to cells with poor or transient data |
Instant method: press Q
Press Q and NSP selects the cell at the current operating point, if it isn't selected already. It then reads target and measured lambda at that instant and adjusts the cell so they should match.
It doesn't blend with neighboring cells. If the engine is sitting on the edge between two cells, the ECU is interpolating between them, but Q only changes one. So hold rpm and load as near the center of the cell as you can before you press it. On a steady-state dyno that's easy. On the street it's much harder.
Give the wideband a moment after each correction. If you press Q again before the new fueling has reached the sensor, you're correcting based on the old reading, and you'll overshoot.
Cell trace method: T, drive, then R
Press T to start a cell trace. You've probably seen the trace line NSP draws through the table as rpm and load move around. With Quick-Tune, NSP also quietly records target and measured lambda for whichever cell is closest to the operating point, many times per second. It keeps a rolling window of up to 2 seconds of samples for each visited cell.
When you're done, select a cell or a range of cells and press R. NSP averages each traced cell's samples and corrects every visited cell in your selection. Unvisited cells are left alone.
Reading the cell colors
While a trace is running, NSP colors every visited cell by comparing its averaged measured lambda with its averaged target, and it updates the colors live:
| Color | What it means |
|---|---|
| Gray | Not visited during this trace, so there's no data |
| White | Measured lambda exactly matched target |
| Light red | Lean, by less than 12% |
| Strong red | Lean by more than 12% |
| Light blue | Rich, by less than 12% |
| Strong blue | Rich by more than 12% |
| Much darker red or blue | On a 4D table (slice axis on), that row and column were only visited on a different slice |
Click any visited cell and NSP shows a line of text above the table with the numbers behind its color. We check a few of those before pressing R, especially on cells that are strongly red. A cell that's badly lean on a single brief visit may just be a tip-in transient, not a base table problem.
A worked example on the dyno
The old way to tune full load was a ramp run, then studying the log, then editing cells by hand, then another run, over and over. With cell trace it looks more like this:
- Confirm injector data, engine setup and target lambda are correct, and the wideband reads accurately.
- Press T and do one controlled ramp run through the rev range. On a boosted car, do one run per boost level you want to cover.
- Check the colors. Click a few red and blue cells to see how far off they are and that they had enough data.
- Select the traced area and press R.
- Do one more ramp run and confirm lambda tracks target across the whole run.
That's often a single confirmation run instead of an afternoon of back-and-forth edits.
Using it on the street
For a solo driver, cell trace is ideal: press T, drive normally for as long as you like, then pull over, select the whole Base Fuel Tuning table and press R. Only cells you actually visited get changed. On your next drive, those areas should sit on target.
Street tuning means watching lambda, knock and temperatures while driving. Have a passenger run the laptop, stay out of heavy load until the map is close, and never do sustained wide-open-throttle pulls on public roads. When in doubt, get it on a dyno.
How O2 control and trims interact
If O2 control is running while you trace, the fuel trim it's applying is included in the Quick-Tune correction. The aim is that after you apply Quick-Tune, the trims can go back to zero. If O2 control long-term fuel trims are enabled, those are applied to the table before Quick-Tune does its work, and NSP tells you when that's happening. Just be aware that trims will change the table along with Quick-Tune.
Troubleshooting Quick-Tune
| Symptom | Usually |
|---|---|
| Cells get worse after pressing R | Wideband lag or bad data from transients. Slow the run down, or apply to a smaller range |
| Corrections look huge everywhere | Injector data, engine size or fuel pressure settings are wrong. Fix the setup, not the table |
| Q changes a cell, but lambda still misses | You weren't centered in the cell, or you pressed it before the wideband settled |
| Nothing happens | Wideband isn't configured or reading, or no cells were visited inside your selection |
Once you've applied changes, Compare Map is a quick way to see exactly what Quick-Tune changed against your previous file.
Quick-Tune FAQ
Can Quick-Tune tune my whole car?
No. It gets the base fuel table close to target lambda. It doesn't touch ignition timing, and it can't judge whether your target lambda is safe for your engine. That's still the tuner's job.
Does it work without a wideband?
No. It needs a configured wideband O2 input to know what the engine is actually doing.
Should I save my map before pressing R?
Always. Save a copy first so you can compare or roll back. If you'd rather have us rough in and finish the map, get in touch.
