Ignition timing

[alfa boxer]

Hello
As I understand it, when you give the engine more fuel the timing advances i.e. on the tps 0 being closed and 100 fully open, ive done a map for the alfa and the driveability is great. So when the throttle is hardly open it has less advance and progressivly gets higher with more fuel/throttle. When I looked at examples of 3d maps in the libary they were all basically the opposite way around to mine i.e higher advance at closed throttle to open throttle. Even the rolling road man agreed with this.Ive tried the map the other way like most of the other examples and it was unresponsive. Now ive got the new firmware in it feels smoother. Very strange.

[Oliver Sedlacek]

I think it would help if you just give a few specific timing figures. At sub 1000 RPM and light throttle, most engines will want at least 20 degrees advance. However, at full throttle and 1000 RPM, the same amount of advance will almost certainly give you major knock, and my own engine wont take more than 10 degrees advanve.

[MartinM]

Remember it's 3D ignition so you have two variables to think about at the same time - rpm and "load", where "load" is either TPS position or measured vacuum (assuming a n/a engine).

Relating advance to "giving an engine more fuel" is a bit too simple.

In the 3D world:
- advance increases with rpm
- advance increases with vacuum (which is why we all used to have "vacuum advance" pipes from manifold to distributor, but now we have MAP-based MJLJs!)

But the terminology is always a bit confusing:
- 0% TPS = closed throttle = minimum load = maximum vacuum = low kPA
- 100% TPS = open throttle = maximum load = minimum vacuum = high kPa

In a traditional map (rpm numbers increase left to right, load numbers increase top to bottom) as shown in the MJLJ Configurator you should have:
- in any row, advance increasing left to right
- in any column, advance increasing bottom to top

So in simple 2x2 MAP-based map you should see something like (with made up figures)

Code: Select all

            low rpm       high rpm
low kPa       20             40
high kPa      10             30

And in simple 2x2 TPS-based map you should see something like (same made up figures)

Code: Select all

            low rpm       high rpm
low TPS       20             40
high TPS      10             30

i.e just the same

As far as I recall, all the maps in the library are this way round (well, they should be!)