Template:Spark Curve

Revision as of 06:02, 31 May 2016; view current revision
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The more compression, the less advance the engine can handle.

• In the distributor, weld the advance slots partially to limit mechanical advance
• Keep the stock vacuum advance (it will have no effect under boost)
• Connect vacuum advance up directly to manifold. This will help idle and starting out under low throttle, but the vacuum advance will have no effect under boost
• Set initial timing at lower than normal, say 3 degrees or 0 degrees
• In the distributor, weld the advance slots partially to limit mechanical advance. For example, maximum advance at 16 psi boost: 23 degrees

Better than all this is to use a fully programmable ignition system with a crank trigger. MegaSquirt and other ECUs can provide initial timing, limited full timing, timing under boost and even retard under boost and compensate for high temperatures.

Consequences of too much spark advance:

cracked pistons, broken ring lands