A lean mixture or detonation can quickly destroy a forced induction engine, even at low boost levels. Likewise too much advance can cause detonation and too much retard can over heat the engine. When tuning under boost it is important to monitor the fuel mixture, exhaust temperature and check that detonation is not occurring. A wide band lambda meter or gas analyzer should be used to monitor the mixture, and tuning aborted at the first sign of an overly lean mixture. A detonation monitor or similar should be used to check that detonation is not occurring. It is also worth monitoring the fuel pressure during tuning to make sure the mixture is not going lean from in sufficient fuel supply. It is a good idea to monitor the exhaust gas temperature as well.

With a forced induction engine, it is recommended that the engine is first tuned without any boost. To do this a supercharger can be disconnected or bypassed, and the waste gate held open for a turbocharger. Intercooler pipes should not be disconnected as this may over-rev the turbo. Compressed air may be used to hold the waste gate open. Once the engine is tuned for the non-boost portion of the tables boost can be introduced gradually and the engine tuned in steps. Otherwise boost tends to increase so sharply so that large portions of the fuel and ignition tables are not mapped.

It is best to over-fuel the engine initially, and gradually lean the mixture out. Most engines will make more power as the mixture is leaned out, but will run hotter and be more prone to detonation. If the engine does not make additional power when the mixture is leaned out then it is best to keep the mixture as rich as possible before the engine loses power. Each engine will respond slightly differently to the mixture settings, so there are no definitely guides to the mixture that will produce the most power or be the most reliable.

With the ignition it is best to start using a setting which is slightly retarded. If the ignition timing is significantly retarded the exhaust manifold and turbo will over heat as the unburned mixture burns in the exhaust manifold. As the ignition timing is advanced peak cylinder pressures increase. Normally this will make more power but places more stress on the engine, particularly the piston and rods. As the ignition timing is advanced at a certain point detonation or pre-ignition will occur. Detonation increases peak cylinder pressures hugely, causes the temperature to rise inside the cylinder and can destroy the engine very quickly.