[jpnovak]

Ignition Maps

Initial timing maps are easy to get set up. Look up a timing curve from the factory manual for your engine build. There are many curves available and they are safe to operate. Program a curve that matches the distributor advance vs rpm across the entire engine load. This will get the engine running and driving. This is just a starting point that will allow the engine to run at full throttle and related to rpm.

Once you have adjusted the fuel trim and have the engine running and driving reasonably well then you can look at options to optimize timing. There are different techniques here. Knock sensors give great feedback. Det-cans (look up detonation cans) connected to a stethoscope or ear muffs can be easily made and work well. Both of these have to be installed while assembling the EFI system and not every install has them. They are not required but just another tool in the toolbox. ( more later)

Here are some Basic rules to follow when adjusting your advance curve. You can use idle advance to tune your idle speed. Chugging or bucking at low speeds means you have too much timing. If the engine runs hot, you do not have enough timing. You can run quite high timing advance under lean load conditions (off throttle and cruise). Advancing the timing during off-throttle will help the car slow down due to more engine braking. If the car feels like its fighting itself you have too much timing. If the engine feel lacking power and lazy there is not enough timing. The leaner the mixture, the slower it burns because the fuel molecules are further apart and therefore the earlier you have to ignite the mixture with advanced timing.

Ideally, this is the one time that using a load Dyno with power absorption readout is super useful. You can manipulate timing on the fly and see power gains/loss. MBT (mean Brake timing) is easy to find in this condition. Timing can make the difference between an engine with a lazy or urgent response.
I will say that timing adjustments may change as you optimize fuel quantity. And, the converse is true. The fuel trim may change (AFR) if the timing is adjusted. Let’s explore that briefly.

With someone else driving the car you can change the timing. Often you can watch the AFR as you advance and retard the timing. Typically, you will find that if you start with the timing conservative (retarded) the AFR will lean out as you advance the timing in a given load cell. The AFR will stabilize lean. This is usually within a degree of MBT optimal timing. Now, you have to do that in the car under controlled conditions for almost each cell in the engine operational space. Fun times.