WHat is detonation or knock on a Toyota Celica GT4

Detonation is quite a complex subject and this article only suggests explanations in basic simple speak! A basic and brief part of an engine cycle...

Normal	Detonation
Piston goes down	Piston goes down
Air is taken into the engine	Air is taken into the engine
Piston starts it's upwards journey	Piston starts it's upwards journey
	Fuel and air goes bang prematurely
Piston reaches top of cylinder - ish	Piston may not reach top of cylinder!
Spark plug "sparks" and ignites fuel	Spark plug fires - may ignite remaining fuel
Fuel and air goes bang	Last bit of fuel and air may go bang
Piston goes down	Piston may go down
Car surges forwards	Car sort of goes forwards/may blow up
Normal engine sound	Tinkling / crap engine sound

Reason	Why?	Cure...
Ignition timing	Too far advanced	Retard the timing
Air sent to cylinders too hot	Poor IC efficiency Hot air drawn into air intake Turbo inefficient	Improve IC efficiency Replace turbo Cold air feed to air intake Fit Water Injection
Turbo inefficient	The boost pressure set is too high for this turbo. The turbo is operating out of its maximum efficiency range producing lots of hot compressed air	Upgrade turbo Run lower boost pressure
Hot spots in the cylinder	Carbon build up Sharp edges/burrs/protrusions	Overhaul Porting and polishing
Lack of fuel/lean mixture	Insufficient cooling by fuel Air fuel ratios rubbish	Add more fuel - larger injectors, increase fuel delivery pressure Sort out you air/fuel ratios You may need a replacement or ECU add on Change the fuel filter Replace the stock fuel pump with e.g. Walboro
Incorrect grade of spark plug	Spark plugs are not dissipating heat quickly enough	Run colder grade plugs
Poor quality fuel	Octane rating low	Run super unleaded - Optimax

Hot spots in the cylinder - overhaul head and remove carbon deposits/sharp edges around valve seats is the definitive cure. To "help" remove these deposits - run Redex, Optimax and Water Injection. WI will have the added benefit of cooling the intake air temperature dramatically.

Lack of fuel - upgrade fuel pump, run larger injectors, fit a fuel pressure regulator, get the car setup by a professional, get an upgraded ECU or ECU add on e.g. Dastek, Apexi S-AFC, MoTec, Haltech, Autronic - have a look here

Poor fuel - put your hand in your pocket and buy super unleaded. Optimax is the highest rated RON petrol in the UK.

Detonation can damage your cylinder head, piston, piston rings, con rods and bearings. Avoid detonation it's expensive.

You should be able to hear a "metallic tinkling sound" from the engine. Often referred to as men with tiny hammers! You should also notice a decrease in engine output power, as the ECU retards the ignition timing. The ECU takes in a signal from the knock sensor to determine when the engine is knocking i.e. detonating. Click here for pictures of the knock sensor.