Engine temperature calibration

A lot of modern petrol engines are run hotter than you would expect – a coolant target
of around 105 degrees at light load is normal on a BMW N55 or B58, an Audi 3.0 TFSI and a
number of others. The engine has a map-controlled thermostat, and the ECU asks for the high
temperature because a hot engine has less friction and cleaner emissions in the test cycle.

The trouble is that it leaves very little headroom. Push the car hard, on a track day or a
hot motorway climb, and the temperature climbs from a high starting point, the ECU starts
pulling ignition timing to protect itself, and the car goes flat. On a tuned car that margin
is smaller still.

What the calibration does

The target temperature is brought down to a conventional figure, typically around 90
degrees, and the fan strategy is adjusted to match. The thermostat opens earlier, the engine
runs with more margin, and it holds its power for longer under sustained load. It is a common
part of a Stage 2 build on these engines and a sensible one on any car that gets driven hard.

What it does not do

It does not fix a cooling system that is not working. If the car is overheating in normal
driving, the thermostat, water pump, radiator or a head gasket wants looking at, and no
calibration will save it. We check that first.

For the trade

This is one of the jobs available through our dealer file service. Send the
original read, tell us the vehicle and what you need, and the file comes back
checked. If a job carries mechanical conditions on the car, they are listed in the
coverage table below and they apply to your customer’s vehicle too.

More about becoming a JFA tuning dealer