People talking about getting det ???? What are you on about cause i've no idea :slap:

Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts

Have a look here for detailed description mate:

http://www.germanmotorcars.com/Detonation.htm

Ohhhhhhhh

 

Cool. THanks. Does this happen before the turbo or in the manifold?

In the cylinder. Not good. It's the petrol/air mix exploding instead of burning. It fubars your piston / engine / crank / con rods etc depending on how bad / terminal it is.

ah, boooo, that doesn't sound good

Roughly (and I'm sure a proper techy would do better) it's down to the fuel/air ratio. If you're running lean (i.e. more air), the mixture gets more prone to exploding. If you're adding more boost, you're adding more air so get more prone to detting. If you're fuelling lean because you can't get enough fuel into the cylinder, you're more prone to detting.

 

But the richer you run (for safety) you burn more fuel and get less power. To get the best power, you need to burn a stochiometric ratio which, for petrol (not sure which octane) is 14.7:1 - i.e. 14.7 parts air by weight to 1 part fuel. Eg my stock TT Z dynod at 266 standard but 285 by running 10% lean.

 

But if you go too far, then the fuel/air mix can dip too lean at just the wrong point in the revs map and then bangety-bang. This explains the importance of the knock sensor (aka det or detonation sensor) - if it detects detting, it goes to safety boost to reduce detting and save your engine.

when you own a zed....... you get into det (debt) pretty quick!! :rofl:

Have a look here for detailed description mate:

http://www.germanmotorcars.com/Detonation.htm

 

Thats cleard things up, what I thought was Det is actually Pre-ignition. :headvswal