Suck Squish Bang Blow part 5 Avoidance of Detonation


aem water injection
AEM’s water injection system is one of the best.  We feel that water injection is one of the best ways to stop detonation in a forced induction car.  It actually reduces overall operating temperature as well due to water’s tremendous latent heat of vaporization.

The least common cause of detonation is glowing sharp areas in the combustion chamber causing the mixture to light off prematurely.

Secondary flame fronts and subsequent detonation can be triggered by these numerous things;

1. over advanced ignition timing
2. poor quality low octane gas
3. too high of a compression ratio
4. glowing hot sharp edges in the combustion chamber
5. too much nitrous, turbo or supercharged boost pressure
6. an engine running too hot
7. too hot of a sparkplug (hot heat range)
8. too lean of an air fuel mixture (burns hot)
9. a mixture richer than 10:1
10. and surprisingly enough, very retarded after TDC timing (which causes the engine to run hot by firing the mixture too late).
11. poorly designed combustion chamber geometry
12. poor water circulation in the head by design
13. turbo system with too much exhaust restriction
14. cam timing
15. non-functioning EGR
16. a combination of several or even all of these things

This list will give you items to look for when eliminating sources of detonation. When modifying your engine, detonation is to be avoided at all costs.  Some engines like rotaries, especially the turbocharged variety, can be destroyed with only one or two pings of detonation.  Unless you are very experienced with rotary engines stick to the factory timing and boost specs.

aem water injection
The AEM water injection system injects a water fog directly into the intake tract.  It cools the intake charge by vaporization and acts in the combustion chambers to slow combustion, in a way just like race gas.  If you overdo the amount of water, you lose power.  The AEM system is very tunable.

By eliminating detonation completely through tuning, you will be amazed with what you can get away with power wise and how much more reliable your tuning endeavors will be.

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