A tuning file is not flash and go
Most people expect to write a file and have the car simply work. Often it does. But a tuned engine asks for more boost, more fuel and more rail pressure than the standard one, and that extra demand exposes faults the standard calibration never reached. When that happens, a new file cannot fix it. Only finding the fault can.
That is why, before any tune, you should always read the fault codes (DTCs) and take a datalog of the car as it is.
What a datalog is
A datalog is a recording of what the ECU asks for and what it actually gets, measured many times a second while the car is driven.
Autotuner offers native logging for most common cars, with the same tool you read the ECU with. For the cars you work on most, or the car you are working on now, ask us for a specific logging solution.
What a datalog shows that nothing else can
- Boost leaks, the most common fault. The ECU requests a boost pressure and the turbo cannot reach it. The log shows requested and actual boost drifting apart. The car feels flat and may go into limp mode, even though the file is fine.
- Rail pressure the pump cannot hold. If the high-pressure fuel pump cannot keep up, actual rail pressure falls below requested at high load. On a diesel that means lost power or limp mode. On a petrol engine it means a lean mixture.
- Other common faults: a clogged fuel filter, a sticking turbo actuator, a faulty MAP or MAF sensor, or a slipping clutch.
Before you tune: fault codes and a stock log
Do this before every tune. A fault found before tuning is one the tune will not be blamed for, and it saves you a comeback.
- Read the fault codes and save them. A stored fault is a problem to fix first: a tune does not fix a fault, and the extra load usually makes it worse.
- Take a datalog of the car as it is, before the file goes in.
- Send both with the job, in the job's messages in the portal.
What to log
A full-throttle pull in 3rd or 4th gear, from low rpm to near the limiter, done safely on a closed road or a dyno. Record:
- Engine speed and pedal position.
- Requested and actual boost.
- Requested and actual rail pressure.
- Requested and actual injection quantity.
- Requested and actual torque.
- Injection duration on a diesel. Lambda, ignition timing and knock correction on a petrol engine.
- Exhaust gas temperature and exhaust back pressure, if the car has those sensors.
After the flash
Log again the same way and check for fault codes. Comparing the two logs shows the file is doing what it should, and if something is wrong, where.
How to send it
Attach the log file to the job's messages in the portal, with the fault codes. Say what the car does and when: under load, when cold, in which gear.
Without a log
Without a log, the tuner can only guess. A file is reworked at no extra cost within 30 days of delivery, and in most cases a rework starts with a datalog.