aggravation

Regarding making adjustments in the ignition maps in the EZK versus adjusting the cam timing....what's the difference or is there?
Is either way of adjusting simply changing the relationship of when the ignition event takes place relative to the valves opening?

Obviously adjusting the cams incorrectly could create valve and piston interference on my S4 that ignition timing adjustments won't but what else makes them different?

EDIT to add: I just remembered - Valve timing adjustments change the relationship of crank/piston position to the valves position where adjusting the ignition timing electronically doesn't change them....I guess that's what makes them different but what is the significance in that to the engine tuner? that is, other than spark to valve position relationship what else are you able to affect by using one over the other?

dr bob

Craig--

Adjusting valve timing affects how well the cylinder fills (and empties...) under different operating conditions. There are issues with the mass of air moving, the sizes of openings (ports and valves), and the speed you expect.

Adjusting ignition timing affects the point in the piston movement where the flame front and subsequent gas expansion occur. Along with the effective cyinder pressure (determined by charge density and effective compression ratio), you adjust ignition timing to maintain gas expansion just shy of 'explosion', staying in the area where the flame front is a nice even controlled wave pushing on the piston top.

The relationship bwteen the two is around the charge density and how it affects flame propogation.


Does that help any?

123quattro

In general, very general, advancing ignition timing under load increases power. Right up to the point where the cylinder knocks due to unstable combustion and ruins your head gasket or breaks your piston. Changing cam timing adjusts the window your engine likes to make power in. Retarding cam timing raises the engine speed where peak power is made. This can be extra useful on a boosted engine running naturally aspirated cams.

Jim bailey - 928 International

85-95 engines changing the cam timing while it would move the ignition rotor should not change the igniton timing the wide tip of the rotor is there so that ignition timing can be varied and the spark generated by the collapse of the coil field can still jump to the cap...

John Speake

................. because igntion timing is related to the flywheel sensor, not to the cam timing.