Timing advance

[asanga]

hi guys, does any one know how the timing is advanced by the ECU on BA 1997 1.8L engine.????

Its not Vacuum advanced.....

[Cosmo Dude]

The timing will be mapped against engine speed and load (RPM, throttle possition, air flow). Base timing can be changed easily enough though.

[asanga]

but how does the ECU physically change the timing , since there is a dizy there must be a way as to how the ECU alter the timing according to load and engine speed

[Cosmo Dude]

In short the ECU de-energises the coil to create the spark based on a signal from a sensor in the distributor (crank angle sensor on V6) and load.

[asanga]

thanks cosmo!

The reason I asked is, when I adjust the base idle (800 RPM) & timing (12 BTDC) by shorting TEN & GND its all good , but when I remove the jumper (TEN & GND) the timing retards to 0 or even lower together with idle speed

[Cosmo Dude]

If you had vac advance then you'd pull the vac before setting the timing. Once you re-attached the vac you'd have the same issue.

[asanga]

there is no vac advance system on BA!

[Cosmo Dude]

No it doesn't and idle doesn't reflect base setting either.

[asanga]

well that's what I thought too! but it seem to be reflecting the base timing. cause if I set base idle to 650rpm and remove the jumper wire, the timing stays at 10-12 BTDC. Anything above 650rpm, timing retards!