- proper fuel octane
- proper spark plug gap
- proper heat range for plug
- proper ignition/spark timing

 

what exactly is spark knock and how do i get rid of it???

Spark knock is just regular engine 'knock' or 'detonation' brought on by either too agressive ignition timing or using a fuel without a high enough octane rating. You can get rid of knock by removing some ignition (2 degrees at a time, generally not more than 4) from the place in the map that the knock is happening at.

The basic idea with knock/detonation is the fuel/air mixture in the cylinder, instead of burning completly and correctly after the skark plug ignites it, explodes all at once, sending a massive instant shockwave to your piston, causing the 'pinging' sound (really sounds more like change in a tin can). The problem is the fuel cannot stand up to the heat and pressure it is being exposed to when it is being combusted and it 'gives up' and just blows up. More octane or less ignition timing will generally fix it. Octane is a direct rating of how resistant to knock/detonation the fuel is, so upping it obviously will help. Removing ignition timing helps by starting the combustion event slighly later, causing less pressure (and less power) to be generated in the cylinder because of the difference in position of the piston in the compression and power stroke when the fuel is ignited.

Pre-ignition is when the fuel ignites BEFORE the plug fires and is VERY deadly for motors -- instead of being an instant 'ping' of force, pre-ignition causes the fuel mixture to be compressed AS it is expanding on the compression stroke across a longer period of time. Pre-igintion usually causes detonation as well, but you cannot tell the difference until your motor simply blows unless you're watching your plugs very carefully. Pre-ignition can be caused by using too 'hot' of plug, cylinder temperatures being way way too high, or left over carbon causing hot spots in the cylinder.

Generally, you won't run into pre-ignition on most setups using normal methods of tuning and the 'knock' you may find is a result of too agressive timing for the fuel you are running and can just be tuned out.

Hope that helps.

Wayne

 

thanks