"Safe" map

[rmaddock]

I was just looking at the new tuner software and noticed, when I loaded the basic map supplied by Brent, that the advance figure decreases in each RPM bin as the KPa figure increases.

Now I'll show my ignorance by asking if all maps should look like this or is it this factor which makes this a safe starter map.

If I am writing my own map, based on what I know of vacuum and centrifugal advances and given RPMs, would the advance figure increase as the KPa does? I.e., looking at the map display, you have the smallest values at the top left and largest at the bottom right?

Thanks in advance.

Robert.

[4600cc]

100 kPA is same pressure as outside.
30 kPA is vacuum you have with throttle shut.

kPA figure will increase as you open throttle, i.e. vacuum will decrease as you open throttle. We tend to decrease advance as vacuum decreases, or decrease advance as kPA increases.

* A good way to think about kPA is to think of it as ENGINE LOAD. If you're using MLJT software to tune, it will already have those labeled as ENGINE LOAD and ENGINE SPEED.

Advance will be decreasing as engine load increases. Also, advance will be increasing as engine speed increases.

[MartinM]

Another good way of thinking...

On 'old-fashioned' distributor-based engines there is a pipe from the manifold to the distributor used for 'vacuum advance'.

i.e when there is a vacuum the ignition is advanced

i.e when the kPa decreases the advance increases