How to datalog an EA888 Gen3: the channels a tuner reads first

Every tier of the tuning service ends with a datalog. Not because the service does not trust the file, but because the file was written from a stock read and the log is the first time the tuner sees the engine actually running it. This is what to record and why.

The channels

Most logging tools for the Gen3 offer a hundred channels. Six of them decide whether the tune is safe.

Engine speed and throttle. Without these the rest cannot be placed. A log is read as "at this rpm, at full throttle, the engine did this".

Boost, requested and actual. Two columns. The request is what the file asked for; the actual is what the turbo delivered. The difference is boost error. A small error is normal; a large one means the turbo cannot meet the request, or a leak is letting it out, and either is worth knowing before the request is raised further.

Timing, and timing pull per cylinder. The advance the ECU ran, and how much it retarded on each cylinder because it heard knock. A healthy Stage 1 on the right fuel shows small, occasional pulls. Sustained pull on one cylinder is a plug, a coil or a mechanical problem, not a tuning one.

Lambda, requested and actual. The mixture. The Gen3's factory wideband reports this directly, which is why no aftermarket gauge is needed for Stage 1. The tuner checks that the actual mixture follows the request under boost and does not go lean at the top of the pull.

Intake air temperature. Because a hot charge knocks sooner, and a log taken after five minutes in traffic in July looks different from one taken on a cool morning. The tuner reads the other channels in the light of this one.

The pull

One log, one pull, full throttle in third gear from about 2,000 rpm to just short of the rev limiter, on a private road, a closed course or a dyno. Third gear, because the load is high enough to show the truth and the speed is low enough to be sane. From low rpm, because the interesting part of a turbo log is how boost builds, not only where it peaks. One clean pull is worth more than ten stitched-together partial ones.

Log at the fastest rate the tool allows. Do it with the car warm, the fuel you declared in the tank, and the air conditioning off.

What a good log looks like

Boost actual tracking request within a psi or so. Timing advancing smoothly with rpm, pull near zero. Lambda holding its target under boost. Intake temperature rising a little through the pull and no more. That log gets a reply that says the car is safe and the order is complete.

What a bad log looks like

Boost falling away at high rpm: a leak or a tired turbo. Timing pull on one cylinder: check that cylinder's plug and coil. Lambda drifting lean at the top: the fuel system is at its limit, which on a stock car usually means a weak pump. Each of those is found by the log and none of them is found by the seat of the pants.

The simulator below cannot log a real car, but its knock gauge shows what timing pull is protecting against. Then, when the car is ready, the booking form is the next step.