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dpetryk · #7 03-12-2002, 05:57 PM

I am curious MB DOC, how do you set the timing?

I know this to be true:

The timing is controlled by the EZL ignition control module. It gets a signal from a crankshaft position sensor located on the flywheel and is not adjustable. One way to change the timing would be to move the position of the sensor (very difficult) or change the value of the reference resistor. But generally speaking there is no need to adjust the timing, it is set by the EZL ignition module.

The EZL ignition control unit contains a microcomputer, pressure sensor and the power output stage for control of the ignition coil. It is fitted to the left wheelhouse and is installed with heat conducting paste. The control unit receives information concerning engine speed (crankshaft position), intake manifold vacuum (load condition), engine temperature (coolant), and full load (throttle valve switch).

The EZL control unit compares information from these inputs with ignition maps for typical load and speed ranges which are stored in the microcomputer. The optimal ignition timing for each operating condition is instantaneously determined from the stored maps and the power output stage switches the primary current of the ignition coil between terminals 16 and 31 of the control unit. Furthermore, a TD (top dead center) reference signal is provided to the CIS-E control unit, tachometer, fuel pump relay, and diagnostic socket.

During cranking and up to approx. 450 RPM, the ignition timing is controlled via the segment edges (fixed) of the flywheel. After approx. 460 RPM has been attained a transition from the fixed ignition timing to dynamic ignition timing (instantaneous, ignition map comparison) is made.

Various ignition characteristic curves are inhibited in the warm-up range depending on the coolant temperature in order to reach the normal operating temperature as rapidly as possible. When a full load signal is received from the throttle valve switch the control unit adapts a fixed full load ignition map characteristic. At temperatures above approx. 203°F the ignition will be retarded to counter any further rise in temperature.

I have attached a typical ignition timing map of the EZL unit. As you can see the timing has a complicated relationship to the various factors that influence it.