What no-load tuning is for
No-load tuning means setting the low-load part of the fuel table with the car stationary, using nothing but the throttle. You're only reaching the lightest-load cells, so it's a starting point, not a tune. What it gives you is an engine that starts, idles and revs cleanly, which is exactly what you want before applying load on a dyno or the road.
Before you touch the map
- Warm the engine fully to operating temperature and let the temperatures settle. Warm-up enrichment and cold running will mess up any numbers you set before that.
- Open the Engine Data page in ESP and check every sensor reads sensibly: coolant and air temp, MAP, throttle position, battery voltage and your wideband.
- Make sure idle is sorted first. Our idle fuel guide covers that step.
The free-rev routine
- Using the throttle alone, bring the engine up to the first RPM row above idle, often 1000 RPM.
- If you're sitting exactly on a row, only that row is being used, which makes the adjustment easy to see. Between rows, the ECU blends the two nearest.
- Adjust fuel until the mixture is at or near stoichiometric, as close as you can get while the engine still runs smoothly without misfiring.
- Move up to the next row (1500, then 2000, 2500, 3000 RPM and so on) and repeat.
When you're done, the engine should start easily and rev cleanly with gentle throttle inputs. Sharp stabs of throttle are a transient fueling problem, which you'll deal with later. QuickTune can speed up the row-by-row work if you have a wideband connected.
Free-revving an unloaded engine at high RPM doesn't teach you much about the tune and puts needless stress on a fresh build. We stop at moderate RPM and leave the rest for when the engine is under load.
Use the free rev as a trigger check
This is also the perfect time to check the trigger. While revving higher, compare the RPM in ESP with what the engine is actually doing. If the reading jumps around, drops out or lags behind, check the Trigger Edge setting in the Trigger setup before going any further. A trigger problem that shows up in neutral will get much worse under load.
Once the free-rev map is sound, move on to tuning the base tables under load.
