Engine Tuning/Chiptuning

Introduction

Chiptuning or remapping is a popular way of tuning any kind of engine, especially turbocharged or supercharged engines since these allow for the biggest gains to be made.
The ECU (Electronic Control Unit) regulates air/fuel ratio's, injection and ignition timing, turbo boost pressure, and many other variables, these can be tweaked to provide up to 10% more power on normal petrol engines, and 20% to 30% more power on turbodiesel engines. Besides having more power and torque available, throttle response and fuel economy are also improved.

A 3D representation of one of the many tables in the ECU

How is chiptuning applied?

Chiptuning is something you normally can't do yourself, special equipment for reprogramming the ECU is required and this is very expensive. Furthermore you need to know what the engine's thermal and mechanical limits are and make sure the car will still meet emission standards. A good tuner performs a before and after dyno test for several reasons:

To determine if the engine is in good condition prior to tuning it
To tweak the ECU maps to get the best performance
To show you the actual result of the tuning

Chiptuning can be done in three ways:

Via the OBD port, the ECU stays in the car and a computer of laptop is connected to the OBD port to reprogram it.
Serial, the ECU is removed from the car but not disassembled, a programmer device is connected to the ECU which is reinstalled in the car after remapping.
Chip, the ECU is removed from the car, and the chip, or chips which hold the data are removed and replaced by remapped ones.

An ECU from a fiat engine

Powerbox

Another way of tuning which some people consider to be chiptuning is installing a powerbox, this is a device which is installed between various sensors (Air flow, temperature, turbo boost, air/fuel ratio, etc.) to fool the ECU into thinking more fuel can be added.
This will most likely cause higher fuel consumption, tons of black smoke in diesel engines due to incomplete combustion, carbon clogging up valves and variable nozzle or vane turbo's. Melting exhaust manifolds, pistons, valves and heads are even possible. This sort of damage is not very common but ECU's going into "safe" mode and cars not passing emission tests are by no means an exception.