What to data log

A good log is the difference between us tuning your car properly and us guessing.
Before you record anything, scan the vehicle for fault codes and note what is
already there. A pre existing fault will change how the engine behaves and we need
to know about it.

What to record on a petrol engine

• Engine speed
• Air mass
• Injection opening time
• Lambda, both specified and actual
• Inlet air temperature
• Exhaust gas temperature
• Boost pressure, both specified and actual
• Wastegate duty cycle (N75 on a VAG car)
• Ignition timing, and any ignition retard

What to record on a diesel

• Engine speed
• Air mass
• Injection quantity
• Injection opening time
• Lambda
• Inlet air temperature
• Exhaust gas temperature
• Boost pressure, both specified and actual
• Wastegate duty cycle

Record the original maximum value and the modified maximum value for each, so
there is something to compare.

How to take a clean log

1. Two people in the car. One drives, one operates the logging tool. Do not try to
   do both.
2. Somewhere safe and legal, and within the speed limit. No log is worth a
   licence.
3. Put the car in the right gear to load the engine properly. Third or fourth on
   most cars.
4. Note where the rev limiter starts, so you know where to stop.
5. Bring the revs down to 1300 to 1500rpm and let them settle.
6. Press record.
7. Full throttle, all the way to just before the limiter.
8. Off the throttle, then stop the recording.

Building up on a Stage 2, Stage 3 or turbo swap

Do not go straight to full throttle on a car with new hardware. Work up in four
passes and read the log each time before you go again.

1. Quarter throttle. 1500 to 3000rpm, then 3000 to 4500, then
   4500 to 6000. Stop and read the log.
2. Half throttle. Same three ranges. Stop and read the log.
3. Three quarter throttle. Same again. Stop and read the log.
4. Full throttle. Only once the first three look right.

At every stage you are checking the same four things: does actual boost follow
requested boost closely, is the ignition timing healthy, is timing being pulled
back, and does the air fuel ratio look safe.

Abort the pull, do not finish it

If anything in the live data looks wrong, come off the throttle and check the
log. Do not complete the run to get a tidy graph. Watch the live data on every
pass and you will not have a problem.

Sending it to us

Attach the log files to your request on the dealer portal along with the fault
code scan. Tell us what the car is doing, not just that it does not feel right, and
say what hardware is fitted.

A note on VAG cars and VCDS

Select the Turbo group, and the UDS button next to it where the car offers it.
Watch the sampling rate on the left of the logging screen: it wants to be at least
4. If it is lower you are asking for too many values at once. Log fewer values and
take a second run for the rest.