Only tune an engine that's mechanically healthy. Start rich and lean it toward your target gradually. Keep an eye on coolant temperature the whole time. If you hear or see detonation, or the mixture goes lean under load, lift off straight away and fix the table before trying again.
Where this fits in the process
This step comes after idle and no-load tuning. By now the engine should idle cleanly and rev freely with good mixtures. Loading it is where the fuel table really gets filled in.
A dynamometer is by far the best way to do it, because you can hold the engine at a fixed speed and load while you adjust. The approach is the same whether it's a chassis dyno with the whole car or an engine dyno with just the motor.
The anchor-and-interpolate method
The idea is simple: carefully tune a handful of cells, then let the software fill the gaps between them with a straight line. You check those in-between cells afterward instead of tuning every single one by hand.
- Pick an RPM column. Hold the engine at a speed that lines up with one of your table's RPM breakpoints.
- Add some load and tune that cell. Bring the throttle in until the engine sits at a load point partway up the table, and adjust fuel until the AFR matches your target.
- Drop back to idle. The idle cell in that column should already be right. If it isn't, go back and finish no-load tuning first.
- Interpolate. Select from the idle cell up to the cell you just tuned and linearize the cells between them. You now have a reasonable estimate for the whole span.
- Repeat, moving up in load until you reach full load, linearizing between each pair of tuned cells.
- Sweep and verify. Ramp through the column and add fuel anywhere it reads leaner than target.
- Move to the next RPM column and do it again, working up the rev range.
By the time you've covered the RPM range this way, the car should drive reasonably well, and you can move on to refining the base tables.
A worked example
Say your table has breakpoints every 500 RPM and every 10 kPa of load. You hold the engine at 2000 RPM, bring in enough throttle to sit at a light-cruise load, and tune that cell. The idle-load cell at 2000 RPM is already right from no-load tuning, so you select the cells between and linearize. Next you add more load, tune a higher cell, and linearize between the two tuned cells. Keep going until you hit full load, then step up to 2500 RPM.
Two rules that keep untuned cells safe
Fuel should rise with load
More air in means more fuel needed. If you tune in injection time, you'll see the numbers climb across the table as load goes up. In VE mode, VE may only creep up slightly, but the calculated injection time still rises because manifold pressure does most of the work, unless VE is dropping off sharply.
After tuning a cell, make sure every cell to its right (higher load) is at least as large. Then when you push into load you haven't tuned yet, the mixture starts out rich rather than lean.
Fuel usually rises with RPM too
As the engine gets more efficient, it generally wants more fuel at higher speeds. This doesn't hold all the way to redline, but using it as a guide means untuned areas err rich. Rich is always the safer mistake.
On a turbo or supercharged engine, fuel demand can climb far faster than a straight line once boost comes in. Tune load points closer together through the boost range so you never interpolate across a wide span.
Don't cook the engine
An Elite changes values in real time, so it's tempting to hold the engine at high load while you adjust. Don't. At mid and high RPM near full load, apply load just long enough to read the mixture, back off, make your change, then load it again to check. That keeps heat and stress down and gives more consistent readings.
Troubleshooting
| Symptom | Usually |
|---|---|
| Goes lean as soon as you enter new load | Cells to the right of the tuned cell are lower than it. Raise them before continuing |
| AFR wanders between tuned points | Tuned points too far apart; add another anchor in the middle |
| Mixture drifts during a long hold | Heat soak. Shorten the time under load |
| Idle cell wrong when you return | No-load tuning not finished; go back and complete it |
FAQ
Can I do this on the street instead of a dyno?
It's much harder to hold steady load and RPM on the road, and much less safe. Features like Quicktune help, but a dyno is the right tool. If you don't have access to one, talk to us.
Why not tune every cell individually?
It burns dyno time and puts needless wear on the engine. Interpolating between well-tuned anchors gets you close, and you correct the rest on the sweep.
