Trans ign and fuel cut ign retard?

[Guest |99|]

Hi Ray,

Q1. When using the 'over run fuel cut' does the ignition retard subtract from the ignition map. ie. if the ignition map is 23 degrees and fuel cut ignition retard is -10 degress the actual ignition during fuel cut is 13 degrees.

Q2. When using the 'transient ignition retard' going from closed throttle to full throttle will both retards (fuel cut & transient) sum together? ie ignition map 23 degress, fuel cut retard -10 degress and transient retard -8 degrees. Ignition timing going from closed throttle to full open throttle would be 23-10-8 = 5 degrees?? with the decay rate being some combination of the fuel cut and transient based on fixed time + degress/cycle + hold time??

If this is the case then it would be possible to actually end up with timing ATDC depending on how the retards are configured.

[Guest |85|]

Based on the conditions you described, logic would dictate the following ignition advance: 23/13/23/15

(hope i did not shoot myself in the foot)

[rayhall]

I believe that is how it should work, but does not do that on my emulator. I am trying to get you an answer.

Ray.

[Guest Marcel B]

I could be wrong , but I would think that the "transient ignition retard" relates to retarding the ignition in an INCREASING transition in the TPS voltage , therefore applying ignition retard when the throttle is opening and not the other way around as in the fuel cut function , I could be wrong :mrgreen:

[Guest |99|]

Your logic is right Marcel and in general there would be no problems. However, the point of the original questions was what happens during the period when going from closed throttle to full open quickly. There is a period of time coming out off fuel cut ignition retard when the ignition returns to the ignition point in the map. It is possible during this time, when the throttle is rapidly opened and the transient ignition operates that the two retards (no poor taste jokes please) will sum together.

[CCS]

Bumping this up. Will both the retard add up?

[Scott]

individual ignition trims will be applied at the same time. For example, a -12 degree 4D ignition trim and a +6 degree 5D ignition trim can both be applied to a +20 degree value from Ignition table 1, giving an ignition angle of 14 degrees BTDC. 20+6-12 = 14.

If you are uncertain about this open the runtime values window (F12 key) and look at the ignition tab. You can see the value from ignition table 1, the various trims, and the actual ignition angle being used.

Scott