505 turbo engine management crash course

[webmaster]

Okay, here's a crash course in N9Txx engine management (paraphrased

from the manual to ensure zero errors):

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The ignition ECU calculates the optimal spark advance and provides an

engine RPM signal for the injection ECU and the tachometer.

The ignition ECU determines the basic spark advance by using:

- The camshaft position via the hall-effect sensor in the

distributor. This is the pulse that gets sent to the injection ECU

and tachometer.

- Engine load percentage via the "basic injection duration" which is

sourced from the injection ECU.

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The ignition ECU then modifies this basic advance factor with the

following data:

- Throttle-open percentage via the TPS and throttle microswitch

(closed throttle)

- Detonation status from each cylinder via the knock sensor

- Electrical system voltage

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The ignition ECU also provides a control for the "Full Load Data"

pin, which provides a signal for a WOT condition to the injection

ECU. BTW, this is pin 18 on the ignition ECU and pin 3 on the

injection ECU.

Notes:

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* "Basic injection duration" is calculated by the injection ECU. It

is basically an indication of air density and is a combination of:

- Engine RPM, from ignition ECU

- Air mass, from AFM metering vane

- Air temperature, from AFM ambient air temp sensor

- Altitude, from Altitude sensor

The engine RPM signal arrives during the ignition ECU's "basic spark

advance" calculation phase. Therefore, the injection ECU is an

integral part of the ignition ECU's most basic function.

* By using the camshaft position data (from distributor), an internal

counter, and the stored detonation information for each cylinder, the

ECU is able to selectively control the spark advance for each

cylinder.

Special thanks to Joe Grubbs for the above writeup

[Guest OB6D]

Quote: "BTW, this is pin 18 on the ignition ECU and pin 3 on the injection ECU."

Weird, i don't even have 18 pins...

On my car it's pin 5 cable number 11 from the knock control unit to pin 11 of the injection modulator.