A general question about Ignition Timing.

Hi All,

I have just started tuning ecu by myself and it's a RX7, I just have two maybe stupid question I want to ask for you guys opinion.

I was told or actually being taught that the more timing advance you can get, the faster the rpm goes up since combustion process will be completed faster. Is this true? (This being in a Natural Aspirated engine)

Secondly, I wanted to ask if the first is true, then in a turbo or Rotary, does it generally help to run abit less timing than I can since the volume of air going into the engine is much more now and in a rotary by design they have less time during the combustion process?

Thanks.

Thomas.

It's not that simple. Be very cautious advancing the ignition timing on a rotary. By the time you notice it's knocking, the damage to the apex seals may already be done.

You need to learn about combustion burn time, and how it is decreased with denser mixtures (so less advance is needed to have peak pressure at the ideal time) and increased with less dense mixtures -- so at part throttle you will need a bit more advance. Since the burn time remains constant, the general trend will be increased advance angle, as the engine speed increases.

Ok... Thanks. I get what you mean and it totally got me thinking again. Maybe I should read up more on combustion time. I have the basic idea I think. Ignite at a time to generate most energy to push down on the piston or push the rotor in a rotation in general but I guess I never put mixture density into the equation.